unit 1.pdf

Introduction to Computer: A computer is a programmable electronic device that accepts raw data as input and processes it with a set of instructions (a program) to produce the result as output. It renders output just after performing mathematical and logical operations and can save the output for fu...

Introduction to Computer: A computer is a programmable electronic device that accepts raw data as input and processes it with a set of instructions (a program) to produce the result as output. It renders output just after performing mathematical and logical operations and can save the output for future use. It can process numerical as well as non-numerical calculations. The term "computer" is derived from the Latin word "compute" which means to calculate. A computer is designed to execute applications and provides a variety of solutions through integrated hardware and software components. It works with the help of programs and represents the decimal numbers through a string of binary digits. It also has a memory that stores the data, programs, and result of processing. The components of a computer such as machinery that includes wires, transistors, circuits, hard disk are called hardware. Whereas, the programs and data are called software. It is believed that the Analytical Engine was the first computer which was invented by Charles Babbage in 1837. It used punch cards as read-only memory. Charles Babbage is also known as the father of the computer. Computer definition Computer A computer is an electronic device, operating under the control of instructions stored in its own memory that can accept data (input), process the data according to specified rules, produce information (output), and store the information for future use. Working of Computer ▪ A computer works on the three basic steps:- Input ↓ Process ↓ Output Functionalities of a computer 1. Accept data 2. Store data 3. Process data as desired 4. Retrieve the stored data as and when required 5. Print the result in desired format. Data, Information and Knowledge Data: Facts and figures which relay something specific, but which are not organized in any way and which provide no further information regarding patterns, context, etc. So data means "unstructured facts and figures that have the least impact on the typical manager.“ Information: For data to become information, it must be contextualized, categorized, calculated and condensed. Information thus paints a bigger picture; it is data with relevance and purpose. It may convey a trend in the environment, or perhaps indicate a pattern of sales for a given period of time. Essentially information is found "in answers to questions that begin with such words as who, what, where, when, and how many". Knowledge: Knowledge is closely linked to doing and implies know-how and understanding. The knowledge possessed by each individual is a product of his experience, and encompasses the norms by which he evaluates new inputs from his surroundings. The content of the human mind can be classified into 3 categories: 1. Data: symbols 2. Information: data that are processed to be useful; provides answers to "who", "what", "where", and "when" questions 3. Knowledge: application of data and information; answers "how" questions The basic parts of a computer are as follows − 1. Input Unit − Devices like keyboard and mouse that are used to input data and instructions to the computer are called input unit. 2. Output Unit − Devices like printer and visual display unit that are used to provide information to the user in desired format are called output unit. 3. Control Unit − As the name suggests, this unit controls all the functions of the computer. All devices or parts of computer interact through the control unit. 4. Arithmetic Logic Unit − This is the brain of the computer where all arithmetic operations and logical operations take place. 5. Memory − All input data, instructions and data interim to the processes are stored in the memory. Memory is of two types – primary memory and secondary memory. Primary memory resides within the CPU whereas secondary memory is external to it. 6. Motherboard: It is the part that connects all other parts or components of a computer. Advantages of Using Computer Now that we know the characteristics of computers, we can see the advantages that computers offer 1. Computers can do the same task repetitively with same accuracy. 2. Computers do not get tired or bored. 3. Computers can take up routine tasks while releasing human resource for more intelligent functions. 4. To increase our productivity. 5. To connects us to the internet. 6. It reduces waste and can store vast amount of data.To improve our employment options. 7. To save the time. 8. To assist the physical challenged. 9. To keep us entertained. 10. To help us automate and monitor. 11. To gave you a better understanding of data. 12. They help us organize, sort and search through information Disadvantages of Using Computer 1. Computers have no intelligence; they follow the instructions blindly without considering the outcome. 2. Regular electric supply is necessary to make computers work, which could prove difficult everywhere especially in developing nations. Limitations of a Computer ▪ They don’t have emotions and feelings. Characteristics of Computer Speed, accuracy, diligence, storage capability and versatility are some of the key characteristics of a computer. A brief overview of these characteristics is - 1. Speed: The computer can process data very fast, at the rate of millions of instructions per second. Some calculations that would have taken hours and days to complete otherwise, can be completed in a few seconds using the computer. For example, calculation and generation of salary slips of thousands of employees of an organization, weather forecasting that requires analysis of a large amount of data related to temperature, pressure and humidity of various places, etc. 2. Accuracy: Computer provides a high degree of accuracy. For example, the computer can accurately give the result of division of any two numbers up to 10 decimal places. 3. Diligence: When used for a longer period of time, the computer does not get tired or fatigued. It can perform long and complex calculations with the same speed and accuracy from the start till the end. 4. Storage Capability: Large volumes of data and information can be stored in the computer and also retrieved whenever required. A limited amount of data can be stored, temporarily, in the primary memory. Secondary storage devices like floppy disk and compact disk can store a large amount of data permanently. 5. Versatility: Computer is versatile in nature. It can perform different types of tasks with the same ease. At one moment you can use the computer to prepare a letter document and in the next moment you may play music or print a document. Computers have several limitations too. Computer can only perform tasks that it has been programmed to do. 6. Consistency: Computer is usually consistent.this means that given the same data and the same instruction.they will produce the same answer every time that particular process is repeated. 7. Automation: A computer is an automatic device. This is because once given the instruction it is guided by this instruction and carry on its job automatically until it is complete. Basic Applications of Computer 1. Home - Computers are used at homes for several purposes like online bill payment, watching movies or shows at home, home tutoring, social media access, playing games, internet access, etc. They provide communication through electronic mail. They help to avail work from home facility for corporate employees. Computers help the student community to avail online educational support. 2. Medical Field - Computers are used in hospitals to maintain a database of patients’ history, diagnosis, X-rays, live monitoring of patients, etc. Surgeons nowadays use robotic surgical devices to perform delicate operations, and conduct surgeries remotely. Virtual reality technologies are also used for training purposes. It also helps to monitor the fetus inside the mother’s womb. 3. Entertainment - Computers help to watch movies online, play games online; act as a virtual entertainer in playing games, listening to music, etc. MIDI instruments greatly help people in the entertainment industry in recording music with artificial instruments. Videos can be fed from computers to full screen televisions. Photo editors are available with fabulous features. 4. Industry - Computers are used to perform several tasks in industries like managing inventory, designing purpose, creating virtual sample products, interior designing, video conferencing, etc. Online marketing has seen a great revolution in its ability to sell various products to inaccessible corners like interior or rural areas. Stock markets have seen phenomenal participation from different levels of people through the use of computers. 5. Education - Computers are used in education sector through online classes, online examinations, referring e-books, online tutoring, etc. They help in increased use of audio-visual aids in the education field. 6. Government - In government sectors, computers are used in data processing, maintaining a database of citizens and supporting a paperless environment. The country’s defense organizations have greatly benefitted from computers in their use for missile development, satellites, rocket launches, etc. 7. Banking - In the banking sector, computers are used to store details of customers and conduct transactions, such as withdrawal and deposit of money through ATMs. Banks have reduced manual errors and expenses to a great extent through extensive use of computers. 8. Business - Nowadays, computers are totally integrated into business. The main objective of business is transaction processing, which involves transactions with suppliers, employees or customers. Computers can make these transactions easy and accurate. People can analyze investments, sales, expenses, markets and other aspects of business using computers. 9. Training - Many organizations use computer-based training to train their employees, to save money and improve performance. Video conferencing through computers allows saving of time and travelling costs by being able to connect people in various locations. 10. Arts - Computers are extensively used in dance, photography, arts and culture. The fluid movement of dance can be shown live via animation. Photos can be digitized using computers. 11. Science and Engineering - Computers with high performance are used to stimulate dynamic process in Science and Engineering. Supercomputers have numerous applications in area of Research and Development (R&D). Topographic images can be created through computers. Scientists use computers to plot and analyze data to have a better understanding of earthquakes. What is Memory? The computer memory holds the data and instructions needed to process raw data and produce output. It is the same as a human mind, where data, information, and instructions are stored. It is a data storage device or a data storage component where instructions for processing data are kept along with the data that has to be processed. Both the input and the output can be held here. The computer memory is divided into large number of small parts known as cells. Each cell has a unique address which varies from 0 to memory size minus one. Computer memory is of two types: Volatile (RAM) and Non-volatile (ROM). The secondary memory (hard disk) is referred as storage not memory. Primary Memory (Main Memory) Primary memory holds only those data and instructions on which computer is currently working. It has limited capacity and data is lost when power is switched off. It is generally made up of semiconductor device. These memories are not as fast as registers. The data and instruction required to be processed reside in main memory. It is divided into two subcategories RAM and ROM. Characteristics of Main Memory 1. These are semiconductor memories it is known as main memory. 2. Usually volatile memory. 3. Data is lost in case power is switched off. 4. It is working memory of the computer. 5. Faster than secondary memories. 6. A computer cannot run without primary memory. Primary memory is of two types: RAM (Random Access Memory): It is a volatile memory. Volatile memory stores information based on the power supply. If the power supply fails/ interrupted/stopped, all the data and information on this memory will be lost. RAM is used for booting up or start the computer. It temporarily stores programs/data which has to be executed by the processor. Advantages of RAM ( Random Access Memory ) There are many advantages of RAM is given below. Disadvantages of RAM ( Random Access Memory ) 1. RAM Faster than secondary storage. There are many disadvantages of RAM, which is given below. 2. RAM can capably read and write any type of data. 1. RAM is an expensive memory. It means costly. 3. RAM consumes less power compared to hard disk, CD, DVD, FLOPPY disk. 2. RAM is slower than the CPU cache memory. 4. No part of RAM moves when RAM executes an 3. RAM memory has limited space for storing data. instruction. 4. RAM is volatile memory means; stored data in RAM 5. RAM memory increases your computer speed. cannot permanent. 6. Central Processing Unit (CPU) reads any data faster because of RAM. Features and Characteristics of RAM 1. RAM memory is capable to do both operations like write and erase. 2. Adding more RAM helps to boost up your computer system speed and working performance. 3. RAM memory allows the CPU to access data faster so that the computer can complete an instruction quickly. 4. RAM is less expensive than SSD, but in comparison to performance, RAM completes any instruction from SSD quickly. RAM is of two types: 1. SRAM (Static RAM): SRAM uses transistors and the circuits of this memory are capable of retaining their state as long as the power is applied. This memory consists of the number of flip flops with each flip flop storing 1 bit. It has less access time and hence, it is faster. Static RAM also known as SRAM. In this RAM the information is stored as long as the power supply is ON. SRAM are of higher coast and consume more power.They have higher speed than Dynamic RAM 2. DRAM (Dynamic RAM): DRAM uses capacitors and transistors and stores the data as a charge on the capacitors. They contain thousands of memory cells. It needs refreshing of charge on capacitor after a few milliseconds. This memory is slower than SRAM. Dynamic RAM also known as DRAM, This type of RAM stores information in a very short times basically, a few milliseconds even though the power supply is ON. The Dynamic RAM is cheaper and of moderate speed and also they consume less power. Characteristics of SRAM Characteristics of DRAM Here, are the important characteristics of SRAM Here, are important characteristics of DRAM 1. SRAM is faster than DRAM 1. Cost-effective 2. Several times more expensive than DRAMs 2. It has a short data lifetime 3. Takes up much more space than DRAMs 3. Requires to refresh 4. Consume less power than DRAMs 4. Slower compared to SRAM 5. Usage: level 1 or level 2 cache 5. More power consumption 6. Cycle time is much shorter compared to DRAM because it does not require to pause between accesses. 7. It is often used only as a memory cache Advantages of SRAM Advantages of DRAM Here, are pros/benefits of using SRAM: Here, are pros/benefits of DRAM: 1. SRAM performance is better than DRAM in terms of 1. Cheaper compared to SRAM. speed. It means it is faster in operation. 2. It has a higher storage capacity. Hence it is used to create a 2. SRAM is used to create a speed-sensitive cache. larger RAM space system. 3. It has medium power consumption. 3. Offers simple structure. 4. It doesn’t require refreshing the memory contents. 5. You don’t need to refresh the memory contents and its access time is faster. Logic or circuitry is needed, so the memory module itself is simpler. Disadvantages of SRAM Disadvantages of DRAM Here are the cons/drawbacks of using SRAM: Here are the drawbacks/cons of using DRAM: 1. It is costlier compared to DRAM. 1. It is comparatively slower than SRAM, so it takes more time for accessing data or information. 2. It is volatile, so you will lose the data when memory is not powered. 2. You will lose data when power is OFF. 3. SRAM does not offer to refresh programs. 3. It has higher power consumption compared to SRAM. 4. It has a low storage capacity. 5. SRAM offers a more complex design. 6. Reduces the memory density. ROM (Read Only Memory): It is a non-volatile memory. Non-volatile memory stores information even when there is a power supply failed/ interrupted/stopped. ROM is used to store information that is used to operate the system. As its name refers to read-only memory, we can only read the programs and data that is stored on it. It contains some electronic fuses that can be programmed for a piece of specific information. The information stored in the ROM in binary format. It is also known as permanent memory. ROM is of four types: 1. MROM (Masked ROM): Hard-wired devices with a pre-programmed collection of data or instructions were the first ROMs. Masked ROMs are a type of low-cost ROM that works in this way. 2. PROM (Programmable Read Only Memory): This read-only memory is modifiable once by the user. The user purchases a blank PROM and uses a PROM program to put the required contents into the PROM. Its content can’t be erased once written. Once a chip has been programmed, the recorded information cannot be changed. It is a non-volatile memory. 3. EPROM (Erasable Programmable Read Only Memory): EPROM is an extension to PROM where you can erase the content of ROM by exposing it to Ultraviolet rays for nearly 40 minutes. EPROM chip can be programmed by erasing the information stored earlier in it. Information stored in EPROM exposing the chip for ultraviolet light. 4. EEPROM (Electrically Erasable Programmable Read Only Memory): You can delete and reprogrammed EEPROM up to 10,000 times. Erasing and programming take very little time, i.e., nearly 4 -10 ms (milliseconds). Any area in an EEPROM can be wiped and programmed selectively. It is programmed and erased by special electrical waves in milliseconds. A single byte of data or the entire contents of the device can be erased. Advantages & Disadvantages of PROM Advantages and Disadvantages of Programmable Read-Only Memory ( PROM ) are given below. Advantages Of PROM Disadvantages Of PROM There is a lot of software available in Data of PROM cannot be modified or the market for programming today, so rewrite if any error has occurred. we don't depend on hardwiring the ROM chip to program. Advantages & Disadvantages of EPROM Advantages and Disadvantages of Erasable Programmable Read-Only Memory (EPROM ) are given below. Advantages Of EPROM Disadvantages Of EPROM EPROM is Non-volatile in nature. EPROM consumes high static power. EPROM is capable to deleted and Takes more time to delete the data of rewrite the program. the EPROM Memory Chip. EPROM Cost-effective than PROM. EPROM is not capable of deleting any specific byte, if you delete one byte of EPROM then all the bytes of EPROM are deleted together. Advantages & Disadvantages of EEPROM Advantages and Disadvantages of Electrically Erasable Programmable Read-Only Memory (EEPROM ) are given below. Advantages Of EEPROM Disadvantages Of EEPROM The data of EEPROM is deleted and The retention time of EEPROM data is upload through electric current. limited. EEPROM is capable of delete and EEPROM is more expensive than other rewriting data an infinite number ROM Chip. of times. Different voltages are required for many The data on the EEPROM chip can be tasks such as deleting and writing deleted byte-wise. data of the EEPROM memory chip. To delete data from EEPROM or to write new data EEPROM does not need to exit that device Advantages of ROM The following are some advantages of ROM: 1. The major advantage of ROM is its non-volatile nature, which helps it retain information even after you turn off the power or shut down the computer. 2. ROM stores all the data necessary for your PC to start and load the operating system. 3. It's a more reliable memory since all of its circuitry is very simple. 4. Compared to other types of secondary memory, MROM is cheaper and more compact. 5. You can use software to program a PROM chip without hard-wiring it. 6. EPROMs are cost-effective as compared to PROM, which allows you to erase and reprogram an EPROM chip multiple times. 7. You can reprogram an EEPROM chip an unlimited number of times without using any additional device, which allows you to erase data bit by bit without erasing the entire content. 8. Flash ROMs have high data transfer rates, are less prone to damage, and can save data without power. Disadvantages of ROM Here are some disadvantages of using ROM: 1. One of the most significant disadvantages of ROM is its slow speed and inability to store large amounts of information. 2. If an MROM contains a design error, you cannot use it, and the code requires replacement. 3. After burning or programming a PROM chip, you cannot erase or change its data. 4. EPROMs consume a lot of static power and take a long time to erase the content, which makes it necessary to remove the entire content to modify it. 5. In contrast to RAM, incorrectly erasing ROM content damages the memory. 6. Flash ROMs are comparatively more expensive than hard disks and there is a limitation on the number of read or writes (R/O) operations that it can perform. Characteristics and Features of ROM There are many characteristics and features of ROM Memory, which are given below. 1. ROM Memory consumes low power. 2. ROM memory is not expensive than RAM. 3. The simple interface of ROM compared to RAM. 4. The testing method of ROM Memory is very simple. 5. ROM is a non-volatile memory. Non-Volatile Means Permanent data that doesn't get deleted. 6. The data of the ROM is not deleted even after the computer shuts down suddenly. 7. ROM is a static nature memory that does not need to be refreshed frequently. 8. ROM Memory is capable to store data for a long time permanently. 9. ROM is a very reliable memory because all the circuits used in this computer memory are very simple. 10. The data of ROM memory is always known, so the data in this memory can be easily verified. 11. All kinds of necessary data are already stored in ROM memory, which is required to start our computer system and load the ope rating system. Secondary Memory This type of memory is also known as external memory or non-volatile. It is slower than main memory. These are used for storing data/Information permanently. CPU directly does not access these memories instead they are accessed via input-output routines. Contents of secondary memories are first transferred to main memory, and then CPU can access it. For example : disk, CD-ROM, DVD etc. Characteristic of Secondary Memory These are magnetic and optical memories It is known as backup memory. 1. Data is permanently stored even if power is switched off. 2. Computer may run without secondary memory. 3. It is a slow memory but reusable. 4. It is a reliable and non-volatile memory. 5. It is cheaper than primary memory. 6. The storage capacity of secondary memory is large. 7. A computer system can run without secondary memory. 8. In secondary memory, data is stored permanently even when the power is off. 9. Portable one can store data and transfer them effortlessly from one device to another. Types of Secondary Memory 1. Floppy Disk – A floppy disc refers to a magnetic disc housed in a square plastic container. It is primarily used to store information and then transfer it from one device to another. There are two sizes of floppy discs (a) Size: 3.5 inches, 1.44 MB storage capacity (b) Size: 5.25 inches and 1.2 MB storage capacity. A computer must consist of a floppy disc drive for using a floppy disc. Such a storage device is now obsolete, and DVDs, CDs, and flash drives have taken its place. A floppy disk is a secondary storage system that consisting of thin, flexible magnetic coating disks for holding electronic data such as computer files. It is also known as Floppy Diskette.The stored data of a floppy disk can be accessed through the floppy disk drive. Since most programs were larger, that required multiple floppy diskettes to store large amounts of data. Therefore, it is not used due to very low memory storage. 2. Compact Disc – A Compact Disc or the CD is a type of secondary storage media that is widely utilized. Its surface is covered in tracks and sectors. It is composed of polycarbonate plastic and has a round form. CDs have a data storage capacity of up to 700 MB. A CD is also known as a CD-ROM (Compact Disc Read-Only Memory) because computers can read the data on it but not write new data onto it. A CD is an optical disk storage device, stands for Compact Disc. It is a storage device used to store various data types like audio, videos, files, OS, Back-Up file, and any other information useful to a computer. The CD has a width of 1.2 mm and 12 cm in height, which can store approximately 783 MB of data size. It uses laser light to read and write data from the CDs. There are two types of CDs: 1. CD-R or compact disc recordable – It is not possible to remove data that has been written onto it; it can only be read. 2. CD-RW or compact disc rewritable – It’s a particular kind of CD that allows us to wipe and rewrite data as many times as we desire, so It’s also known as an erasable CD. 3. Digital Versatile Disc – DVD stands for Digital Versatile Disc. It resembles a CD, but it has a larger storage capacity; up to 4.7 GB of data can be stored. To use a DVD on a computer, a DVD-ROM drive is required. Video files, such as movies or video recordings, are commonly saved on DVDs, which may be played with a DVD player. DVD is an optical disc storage device, stands for Digital Video Display or Digital Versatile Disc. It has the same size as a CD but can store a larger amount of data than a compact disc. It was developed in 1995 by Sony, Panasonic, Toshiba and Philips four electronics companies. DVD drives are divided into three types, such as DVD ROM (Read Only Memory), DVD R (Recordable) and DVD RW (Rewritable or Erasable). It can store multiple data formats like audio, videos, images, software, operating system, etc. The storing capacity of data in DVD is 4.7 GB to 17 GB. There are three different kinds of DVDs available: 1. DVD-ROM or Digital Versatile Disc Read-Only Memory – The manufacturer writes the data on the DVD-ROM, and the users can only read it; they cannot create new data on it. For example, a movie DVD has already been written by the maker, and we can only watch it; we cannot add new data to it. 2. DVD-R or Digital Versatile Disc Recordable – You can write data on a DVD-R, but only once. It is not possible to remove data that has been written onto it; it can only be read. 3. DVD-RW or Digital Versatile Disc RW (Rewritable and Erasable) – It’s a particular kind of DVD that allows us to wipe and rewrite data as many times as we desire. It’s also known as an erasable DVD. 4. Blu-ray Disc – It resembles a CD/VD, but it can actually hold up to 25 Gigabytes data or information. You’ll need a Blu-ray reader if you wish to use a Blu-ray disc. The name Blu-ray comes from the technology used to read the disc: ‘Blu’ comes from a blue-violet laser, and ‘ray’ comes from an optical ray. 5. Hard Disk – A hard disk is a computer's permanent storage device. It is a non-volatile disk that permanently stores data, programs, and files, and cannot lose store data when the computer's power source is switched off. Typically, it is located internally on co mputer's motherboard that stores and retrieves data. It is a large storage device, found on every computer or laptop for permanently storing installed software, music, text documentation, videos, operating system, and data until the user did not delete. 6. Flash Drive – A flash drive or pen drive is available in a variety of storage capacities, including 1, 2, 4, 8, 16, 32, 64 GB, and 1 TB. Da ta is transferred and stored using a flash drive. To use a flash drive, it must be plugged into a computer’s USB port. A flash d rive is quite popular nowadays because it is simple to use and small in size. 7. Solid-state Disk – A Solid-state Disk (SSD) is a data storage and retrieval device that is non-volatile. It’s faster, makes no noise (since it doesn’t have any moving parts like a hard drive), uses less electricity, and so on. If the price is right, it’s a perfect replacement for regular hard drives in laptops and desktops, and it’s also ideal for tablets, notebooks, and other devices that don’t require a lot of storage. 8. SD Card – A Secure Digital Card (SD Card) is commonly used to store data in portable devices such as cell phones and cameras. It comes in a variety of capacities, including 1, 2, 4, 8, 16, 32, and 64 GB. You can access the data present in the SD card by removing it from the device and inserting it into a computer using a card reader. The data in the SD card is stored in memory chips (which are included in the SD card), and there are no moving elements like there are on a hard disc. 9. Pen Drive-A pen drive is a portable device used to permanently store data and is also known as a USB flash drive. It is commonly used to store and transfer the data connected to a computer using a USB port. It does not have any moveable part to store the data; it uses an integrated circuit chip that stores the data. It allows the users to store and transfer data like audio, videos, images, etc. from one computer to any USB pen drive. The storing capacity of pen drives from 64 MB to 128 GB or more. 10. Cache Memory - Cache memory is a very high speed semiconductor memory which can speed up CPU. It acts as a buffer between the CPU and main memory. It is used to hold those parts of data and program which are most frequently used by CPU. The parts of data and programs are transferred from disk to cache memory by operating system, from where CPU can access them. Cache memory uses parallel searching of the required data. it first compare s the incoming address to the address present in the cache. if the address matches , it is said that a hit has occurred. Then the corresponding data is read by the CPU. If the address does not match, it is said that a miss occurred. When a miss occurs, the data is read from the main memory. The data read from the main memory is also written to the cache memory, so that when this specific address is accessed next time a hit occur. Advantages 1. The advantages of cache memory are as follows: 2. Cache memory is faster than main memory. 3. It consumes less access time as compared to main memory. 4. It stores the program that can be executed within a short period of time. It stores data for temporary use. 5. It is faster than the main memory. 6. When compared to the main memory, it takes less time to access it. 7. It keeps the programs that can be run in a short amount of time. 8. It stores data in temporary use. Disadvantages 1. The disadvantages of cache memory are as follows: 2. Cache memory has limited capacity. 3. It is very expensive. 4. Because of the semiconductors used, it is very expensive. 5. The size of the cache (amount of data it can store) is usually small. Register Memory Register memory is the smallest and fastest memory in a computer. It is not a part of the main memory and is located in the CPU in the form of registers, which are the smallest data holding elements. A register temporarily holds frequently used data, instructions, and memory address that are to be used by CPU. They hold instructions that are currently processed by the CPU. All data is required to pass through registers before it can be processed. So, they are used by CPU to process the data entered by the users. Registers hold a small amount of data around 32 bits to 64 bits. The speed of a CPU depends on the number and size (no. of bits) of registers that are built into the CPU. Registers can be of different types based on their uses. Some of the widely used Registers include Accumulator or AC, Data Register or DR, the Address Register or AR, Program Counter (PC), I/O Address Register, and more. Advantages of Register Memory Register memory has the following advantages: 1. It is the fastest memory block hence executes the instructions faster than the main memory. 2. With the help of registers, instructions are handled by the CPU in a very simple way. 3. In today’s digital world, there will hardly be any CPU which does not have registers. Disadvantages of Register Memory Register memory has the following disadvantages: 1. Register memory is small in size so that a large amount of data cannot be stored in it. 2. It is quite expensive as compared to other memory. 3. If the instruction is bigger than the CPU, then the cache or main memory has to be used along with the register for the operation. Types and Functions of Computer Registers: 1. Data Register: It is a 16-bit register, which is used to store operands (variables) to be operated by the processor. It temporarily stores data, which is being transmitted to or received from a peripheral device. 2. Program Counter (PC): It holds the address of the memory location of the next instruction, which is to be fetched after the current instruction is completed. So, it is used to maintain the path of execution of the different programs and thus executes the programs one by one, when the previous instruction gets completed. 3. Instructor Register: It is a 16-bit register. It stores the instruction which is fetched from the main memory. So, it is used to hold instruction codes, which are to be executed. The Control Unit takes instruction from Instructor Register, then decodes and executes it. 4. Accumulator Register: It is a 16-bit register, which is used to store the results produced by the system. For example, the results generated by CPU after the processing are stored in the AC register. 5. Address Register: It is a 12-bit register that stores the address of a memory location where instructions or data is stored in the memory. 6. I/O Address Register: Its job is to specify the address of a particular I/O device. 7. I/O Buffer Register: Its job is to exchange the data between an I/O module and the CPU. Primary Memory Secondary Memory It is also known as temporary memory. It is also known as a permanent memory. Data can be access directly by the processor Data cannot be accessed directly by the I/O or CPU. processor or CPU. Stored data can be a volatile or non-volatile The nature of secondary memory is always non- memory. volatile. It is more costly than secondary memory. It is less costly than primary memory. It is a faster memory. It is a slower memory. It has limited storage capacity. It has a large storage capacity. It required the power to retain the data in It does not require power to retain the data in primary memory. secondary memory. Examples of primary memory are RAM, ROM, Examples of secondary memory are CD, DVD, Registers, EPROM, PROM and cache HDD, magnetic tapes, flash disks, pen drive, memory. etc. What is an Input Device The electromagnetic devices that accept data or a set of instructions from the outside world and then translate that data into machine-readable and understandable form are known as input devices. Computer input devices serve as an interface between the outside world and the computer for proper communication. Characteristics of input devices 1. Below are some characteristics of input devices. 2. Input device allow information to be entered into the computer system in different formats, like audio, image, text, etc. 3. Input device translate the information provided by the user into machine readable form. 4. It is a part of the hardware of computer and can be connected through wire or wireless. 5. To use the computer, Input device is necessary to enter data and input device is easy to use. Need an input device Input devices are crucial today because they enable interaction with and the addition of new data to a computer. Suppose, if a computer have no input devices it could still function, but it would be impossible to change its settings, or perform other common tasks. W ithout an input device we wouldn’t be able to add new data to the computer like text, documents, pictures, etc. Different Types of Input Devices Keyboard For entering data into a computer, the keyboard is the most common and commonly used input device. It contains various keys for entering letters, numbers, and characters. Although there are some additional keys for completing various activities, the keyboard layout is identical to that of a standard typewriter. It is generally available in two different sizes 84 keys or 101/102 keys and for Windows an d the Internet, it is also available with 104 keys or 108 keys. It is connected to a computer system with the help of a USB or a Bluetooth device. The keys on the keyboard are: Numeric Keys: These keys are used to enter numeric data and move the cursor. It is typically made up of 17 keys. Keyboard Shortcuts: These keys include the letter keys (A-Z) and the number keys (09). Control Keys: The pointer and the screen are controlled by these keys. It comes with four directional arrow keys. Control keys include Home, End, Insert, Alternate (Alt), Delete, Control (Ctrl), and Escape. Special Keys: Enter, Shift, Caps Lock, Num Lock, Tab, and Print Screen are some of the special function keys on the keyboard. Function Keys: The 12 keys from F1 to F12 are on the topmost row of the keyboard. Generally, the keyboard is of three types: 1. QWERTY Keyboard 2. AZERTY Keyboard 3. DVORAK Keyboard i) QWERTY Keyboard: It is the most commonly used keyboard with computers in modern times. It is named after the first six letters of the top row of buttons and is even popular in countries that do not use Latin-based alphabet. It is so popular that some people think that it is the only type of keyboard to use with computers as an input device. ii) AZERTY Keyboard: It is considered the standard French keyboard. It is developed in France as an alternative layout to the QWERTY layout and is mainly used in France and other European countries. Some countries have manufactured their own versions of AZERTY. Its name is derived from the first six letters that appear on the top left row of the keyboard. The Q and W keys in AZERTY keyboard are interchanged with A and Z keys in QWERTY keyboard. Furthermore, in AZERTY keyboard M key is located to the left of the L key. AZERTY keyboard differs from QWERTY keyboard not only in the placement of letters but also in many other ways, e.g., it gives emphasis on accents, which is required for writing European languages like French. iii) DVORAK Keyboard: This type of keyboard layout was developed to increase the typing speed by reducing the finger movement while typing. The most frequently used letters are kept in a home row to improve typing Characteristics of Keyboard: 1. The keyboard has various functions keys for a different purpose 2. Instead of using the mouse, we can utilize the arrow keys on the keyboard to do the same purpose as the mouse. 3. The main keyboard, cursor keys, numeric keypad, and function keys are the four primary components of a keyboard. 4. Keyboards are more affordable. Mouse The mouse is the most used pointing device. While clicking and dragging, the mouse moves a little cursor across the screen. If you let off of the mouse, the cursor will come to a halt. You must move the mouse for the computer to move; it will not move on its own. As a result, it’s a device that accepts input. Or we can say that a mouse is an input device that allows you to control the coordinates and movement of the on-screen cursor/pointer by moving the mouse on a flat surface. The left mouse button can be used to pick or move items, while the right mouse button displays additional menus when clicked. It was invented in 1963 by Douglas C. Engelhard. Characteristics of the mouse: 1. A mouse is used to move the cursor on the screen in the desired direction. 2. A mouse allows users to choose files, folders, or multiple files or text or, all at once. 3. Hover over any object with the mouse pointer. 4. A mouse can be used to open a file, folder, etc. You must first move your pointer to a file, folder, and then double-click on it to open or execute. Generally, the mouse is of four types: 1. Trackball Mouse 2. Mechanical Mouse 3. Optical Mouse 4. Wireless Mouse i) Trackball Mouse: It is a stationary input device that has ball mechanism to move the pointer or cursor on the screen. The ball is half inserted in the device and can be easily rolled with finger, thumb or the palm to move the pointer on the screen. The device has sensor to detect the rotation of ball. It remains stationary; you don't need to move it on the operating surface. So, it is an ideal device if you have limited desk space as you don't need to move it like a mouse. ii) Mechanical Mouse: It has a system of a ball and several rollers to track its movement. It is a corded type of mouse. A mechanical mouse can be used for high performance. The drawback is that they tend to get dust into the mechanics and thus require regular cleaning. iii) Optical Mouse: An optical mouse uses optical electronics to track its movement. It is more reliable than a mechanical mouse and also requires less maintenance. However, its performance is affected by the surface on which it is operated. Plain non-glossy mouse mat should be used for best results. The rough surface may cause problems for the optical recognition system, and the glossy surface may reflect the light wrongly and thus may cause tracking issues. iv) Cordless or Wireless Mouse: As the name suggests, this type of mouse lacks cable and uses wireless technology such as IrDA (infrared) or radio (Bluetooth or Wi-Fi) to control the movement of the cursor. It is used to improve the experience of using a mouse. It uses batteries for its power supply.  Joystick A pointing device used to move the cursor around the screen is the joystick. Both the bottom and top ends of the stick have a spherical ball affixed to them. A socket contains the lower spherical ball. You can adjust the joystick in all directions. Trackballs became quite popular in laptops and PCs since they fit neatly inside the case and take up less room when in use. They are more precise and long-lasting than a mouse, which is why they are still utilized. It is invented by C.B.Mirick Characteristics of Joystick: 1. It’s utilized to regulate the cursor’s position across a display screen. 2. It’s utilized in computer games to move the characters and symbols around. 3. It commonly features one or more push buttons, the condition of which can be controlled by the computer as well. Light Pen A light pen is a pointing device that has the appearance of a pen. It can be used to draw on the monitor screen or to pick a menu item. In a small tube, a photocell and an optical system are housed. The photocell sensor element determines the screen location and sends a signal to the CPU when the tip of a light pen is moved across a monitor screen while the pen button is pressed. Characteristics of the light pen: 1. Drawing can easily be changed. 2. It provides the capability of interactive graphics.  Scanner A scanner is a type of input device that works in the same way as a photocopier. It’s used when there’s data on paper that needs to be transferred to the computer’s hard disc for further processing. The scanner collects images from the source and translates them to a digital version that can be saved on the hard disks. These graphics can be changed before they are print ed. Generally, the scanner is of five types: 1. Flatbed Scanner 2. Handheld Scanner 3. Sheet fed Scanner 4. Drum Scanner 5. Photo Scanner Characteristics of Scanner: 1. You can scan film negatives via a scanner if there is a transparent media adaptor. 2. A scanner may also scan low-quality or non-standard-weight paper. 3. The scanners are adaptable, allowing you to scan a wide range of items regardless of their size. You can scan small items as well as large documents if you can locate them. i) Flatbed Scanner: It has a glass pane and a moving optical CIS or CCD array. The light illuminates the pane, and then the image is placed on the glass pane. The light moves across the glass pane and scans the document and thus produces its digital copy. You will need a transparency adapter while scanning transparent slides. ii) Handheld Scanner: It is a small manual scanning device which is held by hand and is rolled over a flat image that is to be scanned. The drawback in using this device is that the hand should be steady while scanning; otherwise, it may distort the image. One of the commonly used handheld scanners is the barcode scanner which you would have seen in shopping stores. iii) Drum Scanner: Drum scanner has a photomultiplier tube (PMT) to scan images. It does not have a charge-coupled device like a flatbed scanner. The photomultiplier tube is extremely sensitive to light. The image is placed on a glass tube, and the light moves across the image, which produces a reflection of the image which is captured by the PMT and processed. These scanners have high resolution and are suitable for detailed scans. iv) Photo Scanner: It is designed to scan photographs. It has high resolution and color depth, which are required for scanning photographs. Some photo scanners come with in-built software for cleaning and restoring old photographs. v) Sheetfed Scanner: In this scanner, the document is inserted into the slot provided in the scanner. The main components of this scanner include the sheet-feeder, scanning module, and calibration sheet. The light does not move in this scanner. Instead, the document moves through the scanner. It is suitable for scanning single page documents, not for thick objects like books, magazines, etc. Digitizer Digitizer is a computer input device that has a flat surface and usually comes with a stylus. It enables the user to draw images and graphics using the stylus as we draw on paper with a pencil. The images or graphics drawn on the digitizer appear on the computer monitor or display screen. The software converts the touch inputs into lines and can also convert handwritten text to typewritten words. It can be used to capture handwritten signatures and data or images from taped papers. Furthermore, it is also used to receive information in the form of drawings and send output to a CAD (Computer-aided design) application and software like AutoCAD. Thus, it allows you to convert hand-drawn images into a format suitable for computer processing. OCR OCR stands for Optical Character Recognition in its full form. OCR is a computer reading technique that reads numbers, characters, and symbols. OCR is a technique for recognizing text in documents that have been scanned into digital form. Optical character recognition (OCR) refers to a device that reads printed text. Character by character, OCR scans the text, converts it to a machine-readable code, and saves it into the memory of the system. OCR also functions as a scanner, scanning documents, photos, images, and handwritten text and storing the information in memory, which may then be compared to previously stored data. Characteristics of OCR: The technology offers a complete solution for form processing and document capture. 1. It has capabilities for defining shapes, scanning, image pre-processing, and identification. Barcode Reader A bar code reader is a device that reads bar-coded data (data that is represented by light and dark lines). To label things, number books, and so on, bar-coded data is often utilized. It could be a standalone scanner or a component of one. A barcode reader is a device that reads barcodes and extracts data from them. The code bar is used to read the bar code printed on any goods. By impacting light beams on barcode lines, a barcode reader identifies existing data in barcodes. Characteristics of Barcode Reader: 1. When a card is inserted, auto-start barcode scanners begin scanning immediately. 2. Reading indicators give the user confirms that the card has been swiped correctly. 3. It’s simple to use, simply hold your phone up to the code and scan it. Web Camera A webcam is an input device since it records a video image of the scene in front of it. It can either be incorporated inside the computer (for example, a laptop) or connected via USB. A webcam is a small digital video camera that is connected to a computer. Because it can capture pictures and record video, it’s also known as a web camera. Characteristics of Web Camera: 1. Webcams are used to allow individuals to see one other while chatting online. This is formally referred to as ‘teleconferencing’. 2. Because webcams can take a picture only if movement is detected in the scene in front of them, they are commonly utilized in burglar alarms and other security systems. 3. Hundreds of webcams can be found all around the world, each pointing to a fascinating scene such as the exterior view of a facility in the Arctic or Niagara Falls. The webcam is connected to a computer that regularly sends an image to an internet server. After that, people connect to the server to view the most recent image. Graphic Tablet A graphics tablet, also known as a digitizing tablet, is a computer input device that allows users to draw drawings and graphics by hand, much like they would with a pencil and paper. A graphics tablet is a flat surface on which the user can draw a picture with the help of an attached stylus, which is a pen-like drawing device. Characteristics of a Graphics Tablet: 1. The graphics tablet is a pressure-sensitive tablet that is controlled by a pen. 2. Drawing, writing, inserting, etc. can be done with the pen. 3. It provides more precision and the ability to monitor (than a touch screen). Digital Camera Digital camera is a device that takes photographs as input. Images are saved on memory cards as data. It comes with an LCD display that allows users to view and review photographs. A digital camera contains photo sensors that record the light that enters into the camera lens. So, when the light strikes the photo sensors, they return the electric current and this electric current is used to create images. Characteristics of Digital Camera: 1. Users can immediately examine images and movies on the LCD screen. 2. All the photos can be stored in the storage device. 3. Users can select and choose the images they want to develop. 4. Easily portable & takes less space. Microphone The microphone is a computer input device that is used to input the sound. It receives the sound vibrations and converts them into audio signals or sends to a recording medium. The audio signals are converted into digital data and stored in the computer. The microphone also enables the user to telecommunicate with others. It is also used to add sound to presentations and with webcams for video conferencing. A microphone can capture audio waves in different ways; accordingly the three most common types are described below: Dynamic: It is the most commonly used microphone with a simple design. It has a magnet which is wrapped by a metal coil and a thin sheet on the front end of the magnet. The sheet transfers vibrations from sound waves to the coil and from coil to electric wires which transmit the sound like an electrical signal. Condenser: It is designed for audio recording and has a very sensitive and flat frequency response. It has a front plate called diaphragm and a back plate parallel to the front plate. When sound hits the diaphragm, it vibrates the diaphragm and alters the distance between the two plates. The changes in distance are transmitted as electric signals. Ribbon: It is known for its reliability. It has a thin ribbon made of aluminum, duralumin, or nanofilm suspended in a magnetic field. The sound waves cause vibrations in the ribbon, which generate a voltage proportional to the velocity of the vibration. The voltage is transmitted as an electrical signal. Early ribbon microphones had a transformer to increase the output voltage, but modern ribbon microphones come with advanced magnets to produce a strong signal Magnetic Ink Character Recognition (MICR) MICR computer input device is designed to read the text printed with magnetic ink. MICR is a character recognition technology that makes use of special magnetized ink which is sensitive to magnetic fields. It is widely used in banks to process the cheques and other organizations where security is a major concern. It can process three hundred cheques in a minute with hundred-percent accuracy. The details on the bottom of the cheque (MICR No.) are written with magnetic ink. A laser printer with MICR toner can be used to print the magnetic ink. The device reads the details and sends to a computer for processing. A document printed in magnetic ink is required to pass through a machine which magnetizes the ink, and the magnetic information is then translated into characters. Paddle: It is a simple input device that is widely used in games. It is a wheel that is held by hand and looks like a volume knob on a stereo that is used to increase or decrease the volume. Paddle moves or controls cursor or any other objects in the game in a back-and-forth motion. It is widely used as an alternative to the joystick. Besides this, the term paddle also refers to many handheld devices designed to control a function in an electronic device, computer, etc. Steering wheel: It is used as an input device in racing video games such as car racing games or in driving programs as virtual simulators to steer a vehicle. It works like the real steering wheel by allowing you to take a right or left turn. A steering wheel may be provided with acceleration and brake pedal devices and a mechanism for shifting gears. Thus, it makes racing games more adventurous and entertaining. Gesture recognition devices: These devices take human gestures as input. There are many such devices that respond to gestures. For example, Kinect is one such device that observes the movement of a player's body and interprets these movements as inputs to video games. This feature is also available in certain tablets and smartphones where you can perform certain tasks such as taking pictures using finger gestures such as swiping, pinching, etc. Light Gun: As the name suggests, it is a pointing input device that is designed to point at and shoot the targets on the screen in a video game, or arcade, etc. The light gun was used for the first time on the MIT Whirwind computer. When the gun is pointed at the target on the screen and the trigger is pulled, the screen goes blank for a fraction of a second. During this moment, the photodiode, which is present in the barrel, determines where the gun is pointed. For example, shooting ducks in a duck hunt game. Touchpad: It is usually found in laptops as a substitute for the mouse. It allows you to move or control the cursor on the screen using your finger. Just like a mouse, it also has two buttons for right and left click. Using the touchpad, you can perform all the tasks that you do with a mouse, such as selecting an object on the screen, copy, paste, delete, open a file or folder, and more. Remote: It is a hardware device designed to control the functioning of a device, e.g., a TV remote that can be used to change channels, increase or decrease the volume, from a distance without leaving the seat. The first cordless TV remote was invented by Dr. Robert Adler of Zenith in 1956. The remote sends the electromagnetic waves to communicate with the device. These waves can be infrared rays, radio waves, etc. Touch screen: It is the display screen of a device such as a Smartphone, tablet, etc., that allows users to interact or provide inputs to the device by using their finger. Today, most of the electronic devices come with touch screen as an alternative to a mouse for navigating a graphical user interface. For example, by touching, you can unlock your phone, open emails, open files, play videos, etc. Besides this, it is used in lots of devices such as Camera, Car GPS, Fitness machine, etc. The concept of the touch screen was first introduced and published by E.A. Johnson in 1965. The first touch screen was developed at the beginning of the 1970s by CERN engineers Frank Beck and Bent Stumped. VR: VR stands for virtual reality. It is an artificial or virtual environment which is generated by computers. A person can interact with virtual objects of this artificial environment using some input devices such as headsets, gloves, headphones, etc. For example, he or she can find himself or herself walking on a beach, watching a football match, walking in the sky, etc., without actually doing all this. Webcam: Any camera which is connected to a computer is called a webcam. The in-built camera provided on a computer can also be considered a webcam. It is an input device as it can take pictures, and can be used to record videos if required. The pictures and videos are stored in the computer memory and can be displayed on the screen if required. Although it works almost the same as the digital camera, it is different from a digital camera, as it is designed to take compact digital photos that can be uploaded easily on the Web Pages and shared with others through the internet. Biometric Devices: Biometrics refers to a process in which a person is identified through his or her biological features such as fingerprints, eye cornea, face structure, etc. It is done by using biometric devices, which can be of different types based on their scanning features and abilities, such as: i) Face Scanner: It is designed to identify a person by scanning his or her face. It takes the face measurements of a person. For example, the distance between eyes, nose, and mouth, etc., accordingly, it confirms the identity of a person. Besides this, it is smart enough to differentiate between a person's picture and the real person. ii) Hand Scanner: The hand of a person can also be used to verify his or her identity as every person has a unique pattern of veins in the palm, just like fingerprints. This device takes advantage of this feature; it identifies a person by scanning the palm of his hand. It uses infrared light to scan veins' patterns and blood flowing in them. Palm is even more unique than fingerprints. iii) Fingerprint Scanner: It scans the fingerprints to identify people or for biometric authentication. This device is developed, keeping in mind the fact that no two persons in the world can have the same fingerprints. It is widely used in companies as a fingerprint attendance system to mark the attendance of employees. This type of scanners captures the pattern of valleys and ridges found on a finger and store it in the memory or database. When you press your finger on the given space, it verifies the identity by using its pattern-matching software. iv) Retina or Iris Scanner: It scans the retina or iris of a person's eye to confirm the identity. This device is more secure than others as it is next to impossible to copy the retina or iris. It works by mapping the retina's blood vessel patterns of the eye. The blood vessels of retina absorb light more easily as well as can be identified with appropriate lighting. In this scan, a beam of low-energy infrared light falls on the retina through the scanner's eyepiece. Then, the software captures the network of blood vessels in the retina and uses it to verify a person's identity v) Voice Scanner: It records the voice of a person and digitizes it to create a distinctive voice print or template. The voiceprints are stored in the database, and are used to verify the voice of a person to confirm his or her identity. The person is required to speak in the normal or same voice that was used to create a voice template. It is not much reliable as it can be misused using a tape recording. Output Devices Output Devices are those devices which show us the result after giving the input data to a computer system. Output can be in different forms like image, graphic audio, video, etc. What is an Output Device? Any peripheral that accepts data from a computer and prints, projects, or reproduces it is known as an output device. The output may be audio, video, hard copy – printed paper, etc. Output devices convert the computer data to human understandable form. We give input to the computer using input devices and the computer performs operations on the data and displays the output to the user using the output device. How Does an Output Device Work In order to show the output, an output device uses a signal it receives from the computer to accomplish a task. An output device’s fundamental operation is listed below as an illustration. 1. If you enter ‘Hi’ on a computer keyboard (input device), the computer receives the signal. 2. Once the input has been processed by the computer, an output device—a monitor—is signaled. 3. The display (output) of the ‘Hi ’ on the screen occurs once the monitor receives the signal. 4. Another example of an output device is a printer, which might print that ‘Hi ’ if it were supported. If the computer was working and had no output device attached, you could still type ‘Hi ’ on the keyboard and it would still be processed. Without an output device, you couldn’t see what happened or verify the input, though. Different Types of Output Devices The various output devices are as below: 1. Monitor A computer’s principal output device is a monitor, often known as a visual display unit (VDU). It displays the processed data like text, images, videos, audios, etc. It makes images by arranging microscopic dots in a rectangular pattern, known as pixels. The sharpness of an image is determined by the number of pixels. There are two types of monitor viewing screens: 1. Cathode-Ray Tube (CRT): This type of monitor is based on a cathode ray tube. In which the cathode ray tube generates a beam of electrons with the help of electron guns they strike on the inner surface of phosphorescent of the screen to generate images. The CRT monitor holds millions of phosphorus dotes in three different colors, i.e., red, blue, and green. These dots glow when the beam struck on them and create an image. The main parts of the CRT monitor are the electron gun, fluorescent screen, glass envelope, deflection plate assembly, and base. 1. Display on a Flat Panel Monitor with a Cathode-Ray Tube (CRT): A flat-panel display is a type of video display with less volume, weight, and power consumption than a CRT. They can be put on the wrist or hang on the wall. Calculators, video games, monitors, laptop, and graphical displays all use flat-panel displays. 2. Plasma Monitor: It is also a flat panel display but it is based on plasma display technology. In a plasma monitor, a small cell is present in between two glass surfaces and these cells contain a solution of noble gases and mercury. So when the electricity supply on the gas present in the cell converts into plasma and produces UV light that creates an image. It is much better than an LCD monitor. The resolution of this monitor is also high up to 1920 x 1920. It has a good contrast ratio, high refresh rate, etc. LCD Monitor The LCD monitor is a flat panel screen that is compact and light-weight as compared to CRT monitors. It is based on liquid crystal display technology which is used in the screens of laptops, tablets, smart phones, etc. An LCD screen comprises two layers of polarized glass with a liquid crystal solution between them. When the light passes through the first layer, an electric current aligns the liquids crystals. The aligned liquid crystals allow a varying level of light to pass through the second layer to create images on the screen. The LCD screen has a matrix of pixels that display the image on the screen.Old LCDs had passive-matrix screens in which individual pixels are controlled by sending a charge. A few electrical charges could be sent each second that made screens appear blurry when the images moved quickly on the screen. Modern LCDs use active-matrix technology and contain thin film transistors (TFTs) with capacitors. This technology allows pixels to retain their charge. So, they don?t make screen blurry when images move fast on the screen as well as are more efficient than passive-matrix displays. LED monitor The LED monitor is an improved version of an LCD monitor. It also has a flat panel display and uses liquid crystal display technology like the LCD monitors. The difference between them lies in the source of light to backlight the display. The LED monitor has many LED panels, and each panel has several LED to backlight the display, whereas the LCD monitors use cold cathode fluorescent light to backlight the display. Modern electronic devices such as mobile phones, LED TVs, laptop and computer screens, etc., use a LED display as it not only produces more brilliance and greater light intensity but also consumes less power. Characteristics of Monitor: 1. Resolution pixels: Pixels are the smallest element of any image 2. Size: The size of the monitor is diagonal measurement of a desktop screen is typically 14 to 25 inches. 3. Refresh Rate: Total number of times per second that an image on a display is repainted or refreshed.  Printer Printers are information output devices that allow you to print data on paper. Or in other words, it is an output device that creates a hard copy of the processed data or information. Printers are divided into two categories: Impact Printer: In impact printers, characters are printed on the ribbon, which is then smashed on the paper. Or we can say that such type of printer uses a print head or hammer to print the data on the paper. Here to print the paper the hammer or print head strikes an ink ribbon against the paper and the character starts printing. The impact printer uses a hammer or print head to print the character or images onto the paper. The hammer or print head strikes or presses an ink ribbon against the paper to print characters and images. Some of the types of impact printers are: 1. Dot matrix printer 2. Daisy wheel printer 3. Line printer 4. Chain printer 5. Character Printers Impact printers have the following characteristics: 1. Extremely low consumable costs. 2. Fairly noisy 3. It’s perfect for large-scale printing because of its inexpensive cost. 4. Physical contact with the paper is required to form an image. Non-Impact Printers: Non-impact printers print characters without the use of a ribbon. These printers are often known as page printers because they print a full page at a time. Some of the types of non-impact printers are: 1. Laser printer 2. Inkjet printer Non-impact printers have the following characteristics: 1. Quicker. 2. They don’t produce much noise. 3. Superior quality. 4. Supports a wide range of fonts and character sizes. Impact printers types. Character Printers Character printer prints a single character at a time or with a single stroke of the print head or hammer. It does not print one line at a time. Dot Matrix printer and Daisy Wheel printer are character printers. Today, these printers are not in much use due to their low speed and because only the text can be printed. Line Printers: Line printer, which is also as a bar printer, prints one line at a time. It is a high-speed impact printer as it can print 500 to 3000 lines per minute. Drum printer and chain printer are examples of line printers. Dot Matrix Printer Dot Matrix Printer is an impact printer. The characters and images printed by it are the patterns of dots. These patterns are produced by striking the ink soaked ribbon against the paper with a print head. The print head contains pins that produce a pattern of dots on the paper to form the individual characters. The print head of a 24 pin dot matrix contains more pins than a 9 pin dot matrix printer, so it produces more dots which results in better printing of characters. To produce color output, the black ribbon can be changed with color stripes. The speed of Dot Matrix printers is around 200-500 characters per second. Daisy Wheel Printer Daisy Wheel Printer was invented by David S. Lee at Diablo Data Systems.It consists of a wheel or disk that has spokes or extensions and looks like a daisy, so it is named Daisy Wheel printer. At the end of extensions, molded metal characters are mounted. To print a character the printer rotates the wheel, and when the desired character is on the print location the hammer hits disk and the extension hits the ink ribbon against the paper to create the impression. It cannot be used to print graphics and is often noisy and slow, i.e., the speed is very low around 25-50 characters per second. Due to these drawbacks,these printers have become obsolete. Drum Printer: Drum printer is a line printer that is made of a rotating drum to print characters. The drum has circular bands of characters on its surface. It has a separate hammer for each band of characters. When you print, the drum rotates, and when the desired character comes under the hammer, the hammer strikes the ink ribbon against the paper to print characters. The drum rotates at a very high speed and characters are printed by activating the appropriate hammers. Although all the characters are not printed at a time, they are printed at a very high speed. Furthermore, it can print only a predefined style as it has a specific set of characters. These printers are known to be very noisy due to the use of hammering techniques. Chain Printer: Chain printer is a line printer that uses a rotating chain to print characters. The characters are embossed on the surface of the chain. The chain rotates horizontally around a set of hammers, for each print location one hammer is provided, i.e., the total number of hammers is equal to the total number of print positions. The chain rotates at a very high speed and when the desired character comes at the print location, the corresponding hammer strikes the page against the ribbon and character on the chain.They can type 500 to 3000 lines per minute. They are also noisy due to the hammering action. Non-Impact Printer: Non-impact printers don't print characters or images by striking a print head or hammer on the ink ribbon placed against the paper. They print characters and images without direct physical contact between the paper and the printing machinery. These printers can print a complete page at a time, so they are also known as page printers. The common types of non-impact printers are Laser printer and Inkjet printer: i) Laser Printer: A laser printer is a non-impact printer that uses a laser beam to print the characters. The laser beam hits the drum, which is a photoreceptor and draws the image on the drum by altering electrical charges on the drum. The drum then rolls in toner, and the charged image on the drum picks the toner. The toner is then printed on the paper using heat and pressure. Once the document is printed, the drum loses the electric charge, and the remaining toner is collected. The laser printers use powdered toner for printing instead of liquid ink and produce quality print objects with a resolution of 600 dots per inch (dpi) or more. ii) Inkjet Printer: The inkjet printer is a non-impact printer that prints images and characters by spraying fine,ionized drops of ink. The print head has tiny nozzles to spray the ink. The printer head moves back and forth and sprays ionized drops of ink on the paper, which is fed through the printer. These drops pass through an electric field that guides the ink onto the paper to print correct images and characters. An inkjet printer has cartridges that contain ink. Modern inkjet printers are color printers that have four cartridges containing different colors: Cyan, Magenta, Yellow, and Black. It is capable of printing high-quality images with different colors. It can produce print objects with a resolution of at least 300 dots per inch (dpi). Plotter A plotter is a device that prints high-quality graphics in a variety of color formats. It works in a similar way to a printer, although it has more advanced features. It is used to print large maps, architectural drawings, large-format printing, and create pictures, 3D postcards, advertising signs, charts, and various designs of the internal structure of building machines, as well as create pictures, 3D postcards, advertising signs, charts, and various designs of the internal structure of building machines. Characteristics of Plotter: 1. Large size prints can be taken via plotters. 2. It is slow and expensive. Projector A projector is a device that allows users to project their output onto a large area, such as a screen or a wall. It can be used to project the output of a computer and other devices onto a screen. It magnifies texts, photos, and movies using light and lenses. As a result, it’s an excellent output device for giving presentations or teaching big groups of people. Characteristics of Projector: 1. They are lightweight, and one person can easily take them out of the box, connect them, and hang an image on the wall. 2. Projectors can be the most cost-effective option for large-screen video in your home. 3. A small projector mounted on a back shelf or bookcase, or mounted on the ceiling, takes up no area on the floor. It is barely visible when it is not in use. 4. A digital projector can be of two types: Liquid Crystal Display (LCD) digital projector: This type of digital projectors is very popular as they are lightweight and provide crisp output. An LCD projector uses transmissive technology to produce output. It allows the light source, which is a standard lamp, to pass through the three colored liquid crystal light panels. Some colors pass through the panels and some are blocked by the panels and thus images are on the screen. Digital Light Processing (DLP) digital projector: It has a set of tiny mirrors, a separate mirror for each pixel of the image and thus provides high-quality images. These projectors are mostly used in theatres as they fulfill the requirement of high- quality video output. Speakers : Speakers are connected to computers to allow sound to be output. For the working of speakers, sound cards are required. From simple two-speaker output devices to surround-sound multi-channel sets, speakers come in a variety of shapes and sizes. They take audio input from the computer’s sound card and output sound waves as audio output. Characteristics of Speakers: 1. Speakers are available in a wide range of qualities and prices. 2. Small, plastic computer speakers with low sound quality are often included with computer systems. Headphones To hear the sound, use ear buds with your computer, laptop, or Smartphone. It enables you to hear the sound without causing any inconvenience to others. To translate electronic signals into sounds without causing inconvenience to others. They can be wired or wireless and can be connected to computers, laptops, mobile phones, etc. They are connected with the devices via Bluetooth. Sound Card Sound cards are computer output devices that are inserted into the computer. A sound card, either external or internal, is required to produce sound on any computer (built-in). An external sound card enables for better overall sound generation and is required for wide and clear sound recording, as well as sound without noise and interference. Characteristics of Sound Card: 1. To listen speakers or headphones, to play games, watch movies, listen to music, or use audio and video conferencing, we use an internal sound card. 2. Frequency is a sound card parameter that represents the number of signals the card processes per unit of time. The frequency is expressed in hertz. The frequency of most sound cards is 96 or 192 kHz. 3. Synthesizers and a variety of electronic musical instruments, such as drums and keyboards, can be connected to your computer using a sound card with standard musical instrument digital interface (MIDI) connections. Video Card An extension card via which a computer can transfer graphical data to a video display device like a TV, or monitor. It processes photos and video, as well as other functions that the CPU generally does. As they have a good processing capability and video RAM, Gamers utilize video cards. Characteristics of Video Card: Heat sinks are required for video cards with high performance as they generate a lot of heat. Also known as graphics card and require software installation in addition to the hardware. When working with huge files, video cards supply a significant quantity of video-only memory that frees up CPU resources, allowing the system to run more effectively. Speech Synthesizer A speech synthesizer is a computerized device that takes in data, interprets it, and generates audible words. It might be a computer card, a box connected by a cable, or software that works with the computer’s sound card. Characteristics of speech synthesizer: Any text, predetermined input can be translated into audible speech. For people who are unable to talk or have impaired vision, it can provide digital verbal communication. It takes in data, interprets it, and generates sound output  GPS The Global Positioning System (GPS) is a radio-based satellite navigation system that uses radio signals to pinpoint a specific position. The sender sends a radio signal to satellites, which collect data such as time, location, speed, and other variables and deliver it to the reception computer for analysis. Because this processed data can be evaluated to obtain information, it is considered as an output device. Characteristics of GPS: 1. GPS satellites constantly communicate their position and time. 2. Solar storms, high storm cover, and other factors impair GPS equipment. 3. The Global Positioning System (GPS) is based on the mathematical idea of trilateration. 4. The GPS works independently of telephonic or internet reception and does not need the user to send any data, however, to improve accuracy both technologies can be used.  Importance of an output device Computer’s output devices obtain information from the computer and send data that has been processed by the computer to the user. Output devices transfer data in human readable forms, like audio, visual, and hard copy media. Name some devices which works as both Output and Input Device Below devices are worked as both input and output devices. Modem: A modem transfer and receives information over cables. Touch Screen: Touch screens gets input from touch and shows the output on the screen. Network Card (NIC): A network card (NIC) works as expansion card for a device that allows the device to connect to the internet. What is a Computer Virus? A computer virus is a program which can harm our device and files and infect them for no further use. When a virus program is executed, it replicates itself by modifying other computer programs and instead enters its own coding. This code infects a file or program and if it spreads massively, it may ultimately result in crashing of the device. Since the computer virus only hits the programming of the device, it is not visible. But there are certain indications which can help you analyse that a device is virus-hit. Given below are such signs which may help you identify computer viruses: Speed of the System – In case a virus is completely executed into your device, the time taken to open applications may become longer and the entire system processing may start working slowly Pop-up Windows – One may start getting too many pop up windows on their screen which may be virus affected and harm the device even more Self Execution of Programs – Files or applications may start opening in the background of the system by themselves and you may not even know about them Log out from Accounts – In case of a virus attack, the probability of accounts getting hacked increase and password protected sites may also get hacked and you might get logged out from all of them Crashing of the Device – In most cases, if the virus spreads in maximum files and programs, there are chances that the entire device may crash and stop working What are some tips to avoid viruses and lessen their impact? 1. Install anti-virus software from a reputable vendor. Update it and use it regularly. 2. In addition to scanning for viruses on a regular basis, install an "on access" scanner (included in most anti-virus software packages) and configure it to start each time you start up your computer. This will protect your system by checking for viruses each time you run an executable file. 3. Use a virus scan before you open any new programs or files that may contain executable code. This includes packaged software that you buy from the store as well as any program you might download from the Internet. 4. If you are a member of an online community or chat room, be very careful about accepting files or clicking links that you find or that people send you within the community. 5. Make sure you back up your data (documents, bookmark files, important email messages, etc.) on disc so that in the event of a virus infection, you do not lose valuable work.  Characteristics of a Virus Viruses have four essential characteristics. 1. SELF REPLICATION: First, viruses are notable for the ability to replicate itself to infect computers, much like its biological counterpart. By replicating itself it is able to spread across computer systems and networks to infect as much as it possibly can. 2. EXECUTABLE PATH: Second, before the virus can do anything, it must be executed. If it cannot be executed, it is harmless. To get itself to replicate it hitches a ride by attaching itself to an executable program. It has to modify the program involved to also execute the virus code. The virus is usually attached to a common executable such as the operating system, which is automatically executed on startup. It may also attach itself to a commonly executed file that a specific company may use. 3. SIDE EFFECTS: Third, viruses do not just contain self-replicating code; they also contain what is called a payload. The payload is similar to a warhead on a missile; it is the side-effect of the virus. The payload has the potential to be malicious, but it does not have to be. 4. DISGUISE: Lastly, the virus will be able to disguise itself before it is noticed by its side-effects. There are two methods of disguise, encryption and interrupt interception. WHAT VIRUSES MAY DO TO A COMPUTER 1. Delete files. 2. Varies messages in files or on programs. 3. Changes volume label. 4. Randomly overwrites sectors on the hard disk. 5. Marks clusters as bad in the FAT (file allocationtable) 6. Replaces the MBR (master boot record ) with own code. 7. Create more than one partition. Computer Viruses 1. Viruses: A virus is a small piece of software that piggybacks on real programs. For example, a virus might attach itself to a program such as a spreadsheet program. Each time the spreadsheet program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other programs) or wreak havoc. 2. E-mail viruses: An e-mail virus travels as an attachment to e-mail messages, and usually replicates itself by automatically mailing itself to dozens of people in the victim's e-mail address book. Some e-mail viruses don't even require a double-click -- they launch when you view the infected message in the preview pane of your e-mail software [source: Johnson]. 3. Trojan horses: A Trojan horse is simply a computer program. The program claims to do one thing (it may claim to be a game) but instead does damage when you run it (it may erase your hard disk). Trojan horses have no way to replicate automatically. 4. Worms: A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well. 5. Boot Sector Virus – It is a type of virus that infects the boot sector of floppy disks or the Master Boot Record (MBR) of hard disks. The Boot sector comprises all the files which are required to start the Operating system of the computer. The virus either overwrites the existing program or copies itself to another part of the disk. 6. Direct Action Virus – When a virus attaches itself directly to a.exe or.com file and enters the device while its execution is called a Direct Action Virus. If it gets installed in the memory, it keeps itself hidden. It is also known as Non-Resident Virus. 7. Resident Virus – A virus which saves itself in the memory of the computer and then infects other files and programs when its originating program is no longer working. This virus can easily infect other files because it is hidden in the memory and is hard to be removed from the system. 8. Multipartite Virus – A virus which can attack both, the boot sector and the executable files of an already infected computer is called a multipartite virus. If a multipartite virus attacks your system, you are at risk of cyber threat. 9. Overwrite Virus – One of the most harmful viruses, the overwrite virus can completely remove the existing program and replace it with the malicious code by overwriting it. Gradually it can completely replace the host’s programming code with the harmful code. 10. Polymorphic Virus – Spread through spam and infected websites, the polymorphic virus are file infectors which are complex and are tough to detect. They create a modified or morphed version of the existing program and infect the system and retain the original code. 11. File Infector Virus – As the name suggests, it first infects a single file and then later spreads itself to other executable files and programs. The main source of this virus are games and word processors. 12. Spacefiller Virus – It is a rare type of virus which fills in the empty spaces of a file with viruses. It is known as cavity virus. It will neither affect the size of the file nor can be detected easily. 13. Macro Virus – A virus written in the same macro language as used in the software program and infects the computer if a word processor file is opened. Mainly the source of such viruses is via emails. 14. STEALTH Virus – these type of viruses use different kind of techniques to avoid detection. they try to trick antivirus programs by appearing like they are necessary files or programs of the OS. Examples Whale Virus What is antivirus software? Antivirus software is used to protect computers from viruses. Viruses can cause a lot of damage to a computer, including deleting files, corrupting data, or even crashing the computer. Antivirus software helps to protect the computer from these threats. It does this by scanning all of the files on the computer for viruses and then deleting or quarantining any infected files. What Does Antivirus Software Do? Various companies create antivirus software and what every one of them offers can be different but all perform the following essential functions: 1. Scan particular files or directories for any malware or predetermined malicious patterns. 2. Allow users to plan scans to automatically run for the user. 3. Allow users to conduct a scan of a selected file or the entire computer, or of a CD or flash drive at any time. 4. Quarantine any malicious piece of program detected, sometimes the user will be notified of such infection and asked if he/she wants to dump the file, other programs will automatically do this in the background. 5. Reminds about the ‘health’ of the computer. 6. Always be sure the user has the best, up-to-date security software installed to protect his/her devices like computers, laptops, tablets, and smartphones. What are the benefits of antivirus software? After discussing what is antivirus software now let’s discuss its benefits. There are several benefits to using antivirus software, including: 1. Protection from viruses: Antivirus software protects your computer from viruses, which can cause damage to your computer or steal your data. 2. Protection from malware: Antivirus software can also protect your computer from malware, which can steal your data or damage your computer. 3. Protection from spyware: Antivirus software can also protect your computer from spyware, which can track what you do on your computer. 4. Protection from other threats: Antivirus software can also protect your computer from other threats, such as phishing attacks. What are the categories of antivirus software? 1. Broadly antivirus software can be divided into three categories cloud-based antivirus software, security software suites, and standalone antivirus software. 2. Cloud-based Software: Cloud-based antivirus software is a relatively new type of antivirus software that relies on cloud computing to scan and clean files. 3. Security Software Suites: Security software suites usually combine multiple security-related functions into a single package, such as antivirus software, firewalls, and spam filters. 4. Standalone Antivirus Software: Standalone antivirus software is the traditional type of antivirus software that installs on a user’s computer and scans files for viruses. 5. Desktop antivirus: This type of antivirus software is installed on a computer and protects it from viruses. 6. Mobile antivirus: This type of antivirus software is installed on a mobile device and protects it from viruses. 7. Web antivirus: This type of antivirus software is installed on a web server and protects it from viruses. 8. Network antivirus: This type of antivirus software is installed on a network and protects it from viruses. Open Source Software (OSS) refers to software that is distributed with its source code made available for anyone to view, modify, and distribute. The core principle of open source is that the software's code is publicly accessible and can be altered or enhanced by anyone, typically under an open source license that ensures these freedoms are preserved. Free Software (a term popularized by the Free Software Foundation) emphasizes the users' freedom to run, modify, share, and distribute software. It promotes the idea that software should respect users' fundamental freedoms. Computer System Hardware A computer system consists of two main components: hardware and software. Hardware refers to the physical components of the computer, which work together to perform various functions. Below is an overview of key hardware components in a computer system. Key Components of Computer Hardware: 1 ) Central Processing Unit (CPU) The CPU is often referred to as the "brain" of the computer. It performs calculations, executes instructions, and processes data. Components: Control Unit (CU): Directs the operation of the processor and coordinates the execution of instructions. Arithmetic Logic Unit (ALU): Handles arithmetic operations (addition, subtraction, etc.) and logical operations (comparisons). 2 ) Input/Output (I/O) Devices Input devices allow users to provide data to the computer. Examples: Keyboard, mouse, touchscreen, microphone, camera. Output devices display or deliver the results of processed data. Examples: Monitor, printer, speakers. 3) Motherboard The motherboard is the main circuit board that houses and connects all the critical components of the computer. It allows communication between the CPU, memory, storage, and other peripherals. Random Access Memory (RAM) RAM is a form of volatile memory that temporarily stores data and instructions the CPU is currently using. It allows for quick read and write operations, which speed up processing tasks. Volatile: Contents are lost when the computer is turned off. More RAM allows the system to run multiple applications simultaneously and handle more intensive tasks. 4) Storage Devices Storage devices are responsible for saving data long-term. Unlike RAM, data in storage is not lost when the computer is powered off. Types: Hard Disk Drive (HDD): Uses spinning magnetic disks to store data. HDDs offer large capacities at lower costs but are slower than SSDs. Solid-State Drive (SSD): Uses flash memory with no moving parts. SSDs are faster and more durable than HDDs but tend to be more expensive for the same storage capacity. Optical Drives: Used to read/write CDs, DVDs, or Blu-rays (less common in modern systems). 5) Network Interface Card (NIC) A NIC allows the computer to connect to a network, whether via wired (Ethernet) or wireless (Wi-Fi) connections. It handles communication between the computer and other devices on the network. 6) Peripheral Devices Peripherals are external devices connected to the computer, expanding its functionality. Examples: Printers, scanners, external hard drives, webcams, and game controllers. Interaction between User and Computer The interaction between a user and a computer involves multiple layers of communication, input, output, and feedback mechanisms. This interaction can be understood in terms of both hardware and software components, enabling users to communicate commands to the computer and receive feedback. Key Aspects of User-Computer Interaction: 1. Input Mechanisms: Users provide input to the computer through various devices. Some of the most common input devices include: Keyboard: For typing text and commands. Mouse or Touchpad: For selecting, dragging, and clicking objects in the graphical user interface (GUI). Touchscreens: Common in smartphones, tablets, and some computers for direct manipulation of objects. Voice Recognition: Allows users to input commands and interact with devices via speech (e.g., Siri, Google Assistant). Gestures: Motion-based inputs, often seen in virtual reality (VR) or systems like Kinect. Sensors: In wearable devices, gestures, or environmental conditions are interpreted as inputs. 2. Output Mechanisms: Once a command is processed, the computer provides feedback to the user via output devices. Common output devices include: Monitor (Display): Visually displays the result of user actions, like graphics, text, and multimedia. Speakers: Provide audio feedback, such as system sounds, music, and spoken information. Printers: Produce hard-copy outputs of documents or images. Haptic Feedback: Used in devices like smartphones or gaming controllers to provide tactile feedback (e.g., vibrations). 3. User Interface (UI): The user interface is where the interaction happens. It is the space where the user interacts with software and controls the system. There are two primary types of user interfaces: Graphical User Interface (GUI): A visual system with windows, icons, and menus. Users interact with elements on the screen through devices like the mouse or touchscreen. Examples include operating systems like Windows, macOS, and Linux distributions. Command Line Interface (CLI): Text-based interface where the user inputs text commands to communicate with th