Computer Classification & Components PDF

**1.6 CLASSIFICATION BASED ON PROCESSING POWER** This classification of computers is based on the processing power and the processing power is in turn based on the computer's word length. Computers in this group are as follows: 1. Mainframe computers. 2. Minicomputers. 3. Microcomputers. **M...

**1.6 CLASSIFICATION BASED ON PROCESSING POWER** This classification of computers is based on the processing power and the processing power is in turn based on the computer's word length. Computers in this group are as follows: 1. Mainframe computers. 2. Minicomputers. 3. Microcomputers. **Mainframe Computers**: These are the traditional large-scale computers that have many peripherals attached to them and so can be used for different purposes simultaneously. Such computers have large main memory and many backup facilities. Therefore, they are usually very large and expensive. Mainframes are normally used in research centres and educational institutions. Examples of mainframe computers include NCR 9300 and the ICL 900 series. **Mini Computers:** These are smaller in size, cost less and have less applicability. They have smaller memory size and word lengths. Examples of mini computers include PDP 11, PDP 8 and the VAX series. **Microcomputers**: Microcomputers are that which has its processor and memory chip mounted on a single board. Microcomputers are smaller and cheaper than minicomputers. However, like the traditional mainframe computers, microcomputer, can be connected to other peripheral devices like scanner, telephone lines e.t.c. **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 are--- **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. **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. **Diligence or Consistency** 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. **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. **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 **MODULE 2** **COMPONENT OF THE COMPUTER** Computer Hardware Difference between RAM and ROM Diagram illustrating the major components of computer Peripheral devices Computer Software Operating systems **COMPONENTS OF THE COMPUTER** There are two main components of the computer. They are: 1. The hardware components. 2. The software components. **1.0 HARDWARE COMPONENTS**: Computer hardware is the collection of physical elements that constitutes a computer system. Computer hardware refers to the physical parts or components of a computer such as the monitor, mouse, keyboard, computer data storage, hard drive disk (HDD), system unit (graphic cards, sound cards, memory, motherboard and chips), etc. all of which are physical objects that can be touched. Hardware components can be further classified into various units as follows: 1. Input unit 2. System unit 3. Output unit(Visual display unit or monitor) **THE INPUT UNIT:** This refer**s** to the device through which data is sent into the Central Processing Unit(CPU) for processing. The most common input device is the keyboard and mouse. Input device is any peripheral (piece of computer hardware equipment to provide data and control signals to an information processing system such as a computer or other information appliance. Input device Translate data from form that humans understand to one that the computer can work with. However all the input devices are important in data processing. The first step in data processing is the sending of data(to be processed) into the CPU where the actual processing takes place, from the CPU, it proceeds to the main memory where it is temporarily stored to be viewed and accessed by the users through the visual display unit(i.e. the monitor). However failure to enter the data correctly yields no useful information or output in accordance to a common computer parlance " Garbage In Garbage Out (GIGO)". Example of Input Devices:- 1.Keyboard 2.Mouse(pointing device) 3\. Microphone --------------------------- -------------------------- -------------------- 4.Touch screen 5.Touch screen 6\. Webcam 7.Touchpads 8\. MIDI keyboard 9.Graphics Tablets 10.Cameras 11.Pen Input 12.Video Capture 13.Video Capture Hardware 14.Microphone 15.Trackballs 16.Barcode reader 17.Digital camera C:\\Users\\user\\Pictures\\INPUT DEVICES.png **Keyboard:** The keyboard is the most important input device on a computer. Computer keyboards have the same layout as standard typewriters. The layout is called QWERTY, because the first six letters on the top row of letters are Q, W, E, R, T and Y. in addition to typing keys, computer keyboards have arrow keys for navigation, function keys for computer-specific tasks, and a calculator-like numeric keypad. **Mouse:** A mouse is a device for controlling the movement of a pointer or cursor on the screen.It consists of a ball which is rolled on a surface. The mouse derives its name from its resemblance to a real mouse. **Joystick:** A joystick resembles a car's gear stick. Moving the stick in any direction results in a corresponding movement of an on-screen object such as a pointer. Joysticks are mostly used for playing computer games. **Digital cameras:** They are used to capture still or moving images, which can be transferred to a computer and manipulated using image or video processing software. **THE SYSTEM UNIT**: This is the central part of the computer. It comprises of the micro processor (i.e. the CPU) and the secondary storage. This is also where peripheral devices such as the mouse, scanner, and telephone etc. are connected for use when they are needed **Central Processing Unit** (CPU) otherwise called the **Microprocessor.** A CPU is brain of a computer. It is responsible for all functions and processes. Regarding computing power, the CPU is the most important element of a computer system. The CPU is comprised of three main parts : - **Arithmetic Logic Unit (ALU**): Executes all arithmetic and logical operations. Arithmetic calculations like as addition, subtraction, multiplication and division. Logical operation like compare numbers, letters, or special characters. - **Control Unit (CU**): controls and co-ordinates computer components. 1. Read the code for the next instruction to be executed. 2. Increment the program counter so it points to the next instruction. 3. Read whatever data the instruction requires from cells in memory. 4. Provide the necessary data to an ALU or register. 5. If the instruction requires an ALU or specialized hardware to complete, instruct the hardware to perform the requested operation. - **Registers :** Stores the data that is to be executed next, \"very fast storage area\". **Primary Memory:-** 1\. **RAM:** Random Access Memory (RAM) is a memory scheme within the computer system responsible for storing data on a temporary basis, so that it can be promptly accessed by the processor as and when needed. It is volatile in nature, which means that data will be erased once supply to the storage device is turned off. RAM stores data randomly and the processor accesses these data randomly from the RAM storage. RAM is considered \"random access\" because you can access any memory cell directly if you know the row and column that intersect at that cell. 2\. **ROM** (Read Only Memory): ROM is a permanent form of storage. ROM stays active regardless of whether power supply to it is turned on or off. ROM devices do not allow data stored on them to be modified. **1.1 DIFFERENCE BETWEEN RAM AND ROM** **NO** **RAM** **ROM** -------- -------------------------------------------------- --------------------------------------------------------- 1 It is volatile It is not volatile 2 It is possible to write and read from RAM It is not possible to write to it.it can only be read. 3 Instructions are alterable by the users Instructions are not alterable by the users 4 It is the word pad of the computer It is not the word pad of the computer 5 It occupies a larger position in the main memory It occupies a smaller position in the main memory  **Secondary Memory:-** Stores data and programs permanently :its retained after the power is turned off. 1\. **Hard drive (HD):** A hard disk is part of a unit, often called a \"disk drive,\" \"hard drive,\" or \"hard disk drive,\" that store and provides relatively quick access to large amounts of data on an electromagnetically charged surface or set of surfaces. Hard disks are used to store your operating system, your application programs (i.e. your word processor, games etc) and your data. They are much faster than CD-ROMs and floppy disks and can also hold much more data. 2\. **Optical Disk**: an optical disc drive (ODD) is a disk drive that uses laser light as part of the process of reading or writing data to or from optical discs. Some drives can only read from discs, but recent drives are commonly both readers and recorders, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives. Optical drive is the generic name; drives are usually described as \"CD\" \"DVD\", or \"Bluray\", followed by \"drive\", \"writer\", etc. There are three main types of optical media: CD, DVD, and Blu-ray disc. CDs can store up to 700 megabytes (MB) of data and DVDs can store up to 8.4 GB of data. Blu-ray discs, which are the newest type of optical media, can store up to 50 GB of data. This storage capacity is a clear advantage over the floppy disk storage media (a magnetic media), which only has a capacity of 1.44 MB. 3\. **Flash Disk** :A storage module made of flash memory chips. A Flash disks have no mechanical platters or access arms, but the term \"disk\" is used because the data are accessed as if they were on a hard drive. The disk storage structure is emulated. **OUTPUT UNIT:** This refers to the channels or mediums through which processed data is displayed. An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system (such as a computer) which converts the electronically generated information into human readable form. C:\\Users\\user\\Pictures\\OUTPUT DEVICES.png Examples of output devices: 1.Monitor 5.LCD Projection Panels ---------------------------------- ------------------------- 2.Computer Output Microfilm(COM) 6.Plotters 3\. Projector 7.Printers (all types) 4.Speaker(s) **Monitors:** The monitor is the computer's display screen. It is also known as visual display unit. The two commonly used technologies for monitors are liquid crystal display and light emitting diodes, which have replaced cathode ray tube monitors that resembled bulky old-fashioned televisions. **Printers:** A printer is a device that expresses text or illustration on paper and other media. The two most commonly used types of printers today are inkjet and laser printers. Inkjet printers work by spraying ink on papers to produce text and characters. On the other hand, laser printers pass abeam on a cylindrical drum, which collects powdered ink (toner) and transfers the toner to paper. Laser printers work in the same way as photocopiers. **Plotters:** A plotter is a device that draws pictures by moving one or more pens on paper. Plotters can be used to produce large printouts. They are typically used by engineers, architects and interior designers who require more precision than can be offered by printers. **1.2 THE MAJOR COMPONENT OF COMPUTER SYSTEM UNIT**.  **Input Unit:** Computers need to receive data and instruction in order to solve any problem. Therefore, we need to input the data and instructions into the computers. The input unit consists of one or more input devices. Keyboard is the one of the most commonly used input device. Other commonly used input devices are the Mouse, Scanner, Microphone etc. All the input devices perform the following functions. Accept the data and instructions from the outside world. Convert it to a form that the computer can understand. Supply the converted data to the computer system for further processing. **Storage Unit**: The storage unit of the computer holds data and instructions that are entered through the input unit, before they are processed. It preserves the intermediate and final results before these are sent to the output devices. It also saves the data for the later use. The various storage devices of a computer system are divided into two categories. a\) **Primary Storage:** Stores and provides very fast. This memory is generally used to hold the program being currently executed in the computer, the data being received from the 2 input unit, the intermediate and final results of the program. The primary memory is temporary in nature. The data is lost, when the computer is switched off. In order to store the data permanently, the data has to be transferred to the secondary memory. The cost of the primary storage is more compared to the secondary storage. Therefore, most computers have limited primary storage capacity. b\) **Secondary Storage:** Secondary storage is used like an archive. It stores several programs, documents, data bases etc. The programs that you run on the computer are first transferred to the primary memory before it is actually run. Whenever the results are saved, again they get stored in the secondary memory. The secondary memory is slower and cheaper than the primary memory. Some of the commonly used secondary memory devices are Hard disk, CD, etc., **Memory Size**: All digital computers use the binary system, i.e. 0's and 1's. Each character or a number is represented by an 8-bit code. The set of 8 bits is called a byte. A character occupies 1-byte space. A numeric occupies 2-byte space. Byte is the space occupied in the memory. The size of the primary storage is specified in KB (Kilobytes) or MB (Megabyte). One KB is equal to 1024 bytes and one MB is equal to 1000KB. The size of the primary storage in a typical PC usually starts at 16MB. PCs having 32 MB, 48MB, 128 MB, 256MB memory are quite common. **Output Unit**: The output unit of a computer provides the information and results of a computation to outside world. Printers, Visual Display Unit (VDU) are the commonly used output devices. Other commonly used output devices are Speaker, Headphone, Projector etc. **Arithmetic Logical Unit**: All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. It also does comparison and takes decision. The ALU can perform basic operations such as addition, subtraction, multiplication, division, e.t.c and does logic operations viz, \>, **1.3 PERIPERAL DEVICES** They are devices attached to the system to help perform one given task or the other. They can be classified as input devices, output devices or storage devices like tape units. Peripheral input devices are those that are used to read or pass instructions to the computer Examples of peripheral input devices includes card reader, mouse, joystick etc. Peripheral output devices are those that are used to receive the result of processed data from the Central Processing unit (CPU)e.g. printer ,graph plotter etc.