Computer Fundamentals PDF

 1 C Computer Fundamentals H COMPUTER CONCEPTS A P T E R LEARNING OBJECTIVES ⚫ To understand the basic concepts of computer system ⚫ To know the uses of computers in various fields ⚫ To understand the computing process ⚫ To...

 1 C Computer Fundamentals H COMPUTER CONCEPTS A P T E R LEARNING OBJECTIVES ⚫ To understand the basic concepts of computer system ⚫ To know the uses of computers in various fields ⚫ To understand the computing process ⚫ To understand the characteristics of computers ⚫ To do the classification of computers ⚫ To discuss various generations of computers ⚫ To understand the various functions of CPU ⚫ To know the concept of Virtual Memory ⚫ Memory management 1.1 COMPUTER In the simplest definition, a computer is an electronic device - a flexible machine that can manipulate data. Computer is being used for tasks as adding up the supermarket bill, getting cash at an ATM, computers are also used by writers, television producers, musicians, poets, graphics illustrators and scholars of medieval history. A computer is programmable i.e. the computer depends totally on the program, which the computer is using. (A program is a list of instructions, telling the computer ‘What to do.') A computer’s hardware (the machine and its components) is designed to be as flexible as possible. By using computer programs, called software, one transforms this flexible hardware into a tool for a specific purpose. No matter which program a computer is using, the machine itself performs only four basic operations, as shown in Fig. 1.1.1. The most widely accepted definition of the computer includes the following operations: 2 Computer For Managers  Computer Concepts CPU Processing Unit Monitor Printer Data Fig. 1.1.1: Different Computer Operations ⚫ Input: A computer accepts data that is provided by means of an input device, such as a keyboard. ⚫ Processing: A computer performs operations on the data to transform it in some way. ⚫ Output: A computer produces output on a device, such as a printer or a monitor, that shows the results of processing operations. ⚫ Storage: A computer stores the results of processing operations for future use. This definition is often referred to as the IPOS cycle. The four steps of the IPOS cycle-input, processing, output, storage - do not have to occur in a rigid IPOS sequence. Under the direction of a program, a computer uses the steps of this process when needed and as often as needed. The use of a personal computer, a computer designed to meet an individual’s computing needs, illustrates these four basic computer operations. We use the keyboard for taking the input data. The computer’s internal circuitry processes the data. We see the results (output) on the computer’s monitor (the TV-like display) and we can print these results on the printer. We can also store the results on the computer’s internal disk or on a removable disk. Fig. 1.1.2 depicts this relationship. Fig. 1.1.2: Relationship between different parts of a Computer The system unit contains the components with which the computer processes and stores data. The keyboard and the mouse are input devices. The monitor displays the output. The printer prints the output. Computer For Managers 3 1.2 USES OF COMPUTER The purpose of the computer is to transform data into information. In this context, data means some kind of unorganized material that can be entered into the computer - a rough sketch that needs work, a first draft of an essay that needs revision or polishing, figures from a company’s books, a list of names and addresses. What results from processing operations is information, i.e. data that has been made meaningful and useful. This capability to process data can be used in a variety of ways. People have come up with some very interesting uses. A psychologist keeps a computer in the counselling room. At the touch of a key, the psychologist can search through references on a computer disk for information relating to topics that come up during counselling sessions. 1.3 ELEMENTS OF THE COMPUTING PROCESS Computers consist of hardware, the physical parts of the computer and software, the programs that tell the computer 'what to do.' Processing data into information (the computing process) involves more elements than just hardware and software. All these elements must be organized so that each works smoothly and efficiently with the others. In the computing process, computers integrate the use of five key elements which are given as follows: ⚫ Hardware ⚫ Software ⚫ Data ⚫ People ⚫ Procedures The computing process, in short, includes everything and everyone necessary for the computer to perform a useful task. The following sections show that ‘how each of these elements works in the process’. 1.3.1 Hardware The term hardware refers to the physical parts of the computer. Computer hardware is versatile-but it does depend on the computer program, we use. The key to the computer’s versatility is memory. One can think of memory as a temporary workspace. The computer’s processor uses this workspace as a scratch pad during processing. Many people confuse memory with storage. Memory is temporary. When we turn off the computer, everything in the memory is lost. Storage is usually permanent. On most computers, storage also has far greater capacity than memory. Understanding the distinction between memory and storage is essential. Some programs keep their output in memory. One must transfer this information to a storage device, such as a disk drive, if one wants to keep the information permanently. If we switch off the computer without saving this information (transferring it to storage), the information is lost. The key to the computer’s precision is the fact that it represents data digitally. Computers use binary digits, using a base 2 number system rather than a decimal (or base 10) number system. A binary digit, commonly called a bit, has a value of either 0 (zero) or 1 (one). Eight bits are grouped together to represent a character - a letter, number or special character. This group is called a byte. Many people use the terms character and byte to mean the same thing. People talk about bytes when they talk about the capacity of computer memories and storage devices. Because one byte can store only one character, these devices must be capable of storing thousands, millions or even billions of bytes. To describe these large capacities, the terms kilobyte 4 Computer For Managers (KB), megabyte (MB) and gigabyte (GB) are used. A kilobyte equals approximately one thousand bytes, a megabyte equals approximately one million bytes and a gigabyte equals approximately one billion bytes. (The actual number of bytes in a megabyte is slightly higher because computer storage amounts are actually measured in base 2 numbers.) 1.3.2 Software Software is the set of instructions (also called a program) that guides the hardware through its job. The following sections explore additional aspects of software. (a) Programming Languages: Software programs must be written in programming languages. Programmers i.e. people trained in the use of a programming language, write programs. (b) System and Application Software Packages: Today’s complex computer programs, such as Microsoft Word (a word processing program), consist of many separate programs that are designed to run together. In recognition of this fact, people sometimes speak of software packages. When we buy Microsoft Word, we are actually buying a software package rather than a single program. Based on the function of the package, software packages are divided into two categories: system software and application software. Computer literacy involves; learning that 'how to use both system software and one or more application programs'. Computers need system software to function. System software integrates the computer’s hardware components and provides tools for day-to-day maintenance tasks, such as displaying a list of the files contained on a disk. MS-DOS, UNIX, Microsoft Windows 98 and System 7 are well-known examples of system software. (c) Application software: It turns the computer into a tool for a specific task, such as writing. Not all application programs will be useful to us. Some application programs are special-purpose programs, which perform a specific task for a single profession. For example, safety managers use a program that prints records of occupation-related injuries and illnesses in a format required by a government health bureau. If we aren’t a safety manager, we would not find this application program interesting or useful. Other application programs are called general-purpose programs. People use these programs for a variety of tasks. Commonly used general-purpose programs include the following: ⚫ Word processing: More than 85 per cent of the personal computers are equipped with a word processing program, which transforms the computer into a tool for creating, editing, proofing, printing and storing text. Many of today’s books originated in text typed into computers-including this one also. ⚫ Desktop publishing: In the past, newsletters and magazines were created through an expensive, tedious process called layout, in which someone does the job of cut and pasting photographs, borders and text to create a pleasing design. With the help of the desktop publishing software in the computer, we can produce attractive results with a little special training. ⚫ Electronic spreadsheet: Businesses previously worked out budgets and made forecasts using accountant’s paper and a calculator. Electronic spreadsheet programs enable us to type the headings and numbers into a computerized version of accountant’s paper, but with a twist. We can hide formulae within the on-screen 'paper.' These formulae perform computations on the data. The payoff is that one can change any number and immediately see the effect of the change. People use electronic spreadsheets for many purposes, not just business-related ones. For example, a forest ranger uses an electronic spreadsheet to analyse data concerning endangered animal populations. Computers For Managers 5  ⚫ Database: A database program creates an electronic version of a card file-and the program gives us the tools, needed to organize this file (for example, by alphabetizing it) and to retrieve information. An eighth-grade English teacher, for instance, could create a database of interesting uses of language - and retrieve examples for use in class discussions. ⚫ Telecommunications software: These software transforms a computer into a terminal, which can connect to a multiuser computer system by means of the telephone. Commercial multiuser systems enable us to join discussion groups, exchange mail with other users, make plane and hotel reservations and obtain free software for our computer. ⚫ Graphics software: Are we going to give a public presentation in our future? If so, we need to learn 'how to use presentation of Graphics programs to create attractive charts and graphs that you can share with the audience.' 1.3.3 Data Computers transform data into information. Data is the raw material; information is processed data. Data is the input to the processing; information is the output. A useful model to describe the relationship between data and information is called the systems model. It shows that data goes into a process and information is then output. Fig. 1.3.1 describes this model. INPUT PROCESSING OUTPUT SOFTWARE INFORMATION INSTRUCTIONS 14 Add 5 numbers REPORT 32 170 85 Divide by 5 The average 16 34 number is 34 23 Data consists of these Software instructs the This information is 5 numbers computer to process presented in a report the data Fig. 1.3.1: A System Model Several characteristics distinguish useful information from data. The purpose of information is to help people for making well-informed decisions, but what makes information useful? Information must be relevant, timely, accurate, concise and complete in order to be useful. Data must be accurate but doesn’t need to be relevant, timely or concise. Table 1.3.1 describes these characteristics. 6 Computer For Managers  Characteristics Description Relevant Information applies to the current situation. Timely Information is up-to-date and available when it is needed. Accurate Data given to the computer and the output are correct in every detail. Concise Information is condensed into a usable length. Complete All important items are included. Table 1.3.1: Characteristics of useful information 1.3.4 People One may be surprised to learn that people are part of the computing process. Some computers, such as the computer chip that controls an automobile engine, function without human intervention. But even these computers were designed by people and occasionally require maintenance by people. Most computers require people, who are called users (or sometimes end users). Some users progress beyond the basics of computer literacy. They learn the advanced features of application programs. With this knowledge, these users can customize an application program for a specific task. These knowledgeable people are called power users. Computer professionals have taken intermediate and advanced courses about computers. These people apply their professional training to improve the performance, case of use and efficiency of computer systems. One kind of computer professional is the programmer, who creates new computer programs. Excellent career opportunities exist for students interested in becoming computer professionals. 1.3.5 Procedures Procedures are the steps that one must follow to accomplish a specific computer-related task. Part of a user’s computer literacy is, knowing common procedures. We already know several computer procedures. For example, we have probably used an Automated Teller Machine (ATM). Inside, the ATM is a computer. In response to the on-screen messages, called prompts, we insert our card, enter our Personal Identification Number (PIN) and tell the machine how much money we want. 1.4 CHARACTERISTICS OF COMPUTERS No matter where computers are found or how they are applied, they’re used for input, processing, output and storage. But computers wouldn’t be worth the trouble without the following characteristics: ⚫ Computers are fast. Many of today’s computers can perform hundreds of millions of processing operations in one second. ⚫ Computers are reliable. Today’s computers may run day in and day out for years without failure. ⚫ Computers are accurate. The computer’s physical processing circuits rarely make errors. Computers make errors, of course, but there are almost always due to faulty programs or incorrect data input. ⚫ Computers can store massive amount of information. Today’s personal computers can be equipped with disks capable of storing more than forty billion characters (letters or numbers). That capacity is enough to store the complete works of William Shakespeare, an unabridged English dictionary, a 32-volume encyclopedia, a world atlas and almanac, dozens of computer Computers For Managers 7  programs and all our written work from the third grade through graduate school with room for more. ⚫ Computers can move information very quickly from one place to another. Using all experimental connection that may soon play a role in the Information Superhighway, one computer can send the entire text of the Encyclopaedia Britannica to another linked computer in less than one second. A computer-literate person knows that the computer is a tool for creating useful information that can be printed, communicated to others and stored for future use. ⚫ 1.4.1 CENTRAL PROCESSING UNIT (CPU) In order to work, a computer needs some sort of “brain”. At the core of each computer, there is a device called central processing unit (CPU), which is the brain of the computer. CPU reads the program from the main memory, and executes each step of the program, which may involve calculations and decision-making. The CPU is responsible for controlling all devices of the computer. It initiates a memory operation, which may involve reading data from an input device and storing it into memory or read data from the memory and display it on an output device. The CPU mainly consists of three parts— Control Unit, Arithmetic Logic Unit (ALU), and Primary Storage (also referred to as Main Memory). The ALU is the unit, which performs all mathematical calculations and logical operations. It performs addition, subtraction, multiplication, and division. It performs a logical operation by comparing two numbers. It can determine the smaller number, larger number or determine if the two numbers are equal. It can also determine whether a number is positive, negative or zero. A program is a sequence of instructions. An instruction may be an arithmetic operation, a logical operation, an assignment, or a jump. The control unit sequentially accesses program instructions, decodes them, and directs ALU, Main Memory, input devices, and output devices so that the program instructions can be carried out. Execution of one program instruction may require control unit to issue many directives. The ALU may also perform many operations to complete one program instruction. Each operation performed by ALU and control unit is referred to as machine instruction. Each program instruction may involve many machine instructions. A single machine instruction is completed in a machine cycle. The number of machine instructions completed in a second is called the speed of the CPU and it is measured in MIPS (Millions of instructions per second). A CPU also contains a set of registers, which are specialized, small, high-speed memory for storing temporary results of ALU and for storing control information. Computer Speed The word length of a CPU is the number of bits it can process in a single cycle. A 64-bit machine can process 64 bits in a single cycle. A 64-bit machine is faster than a 32-bit machine. The cycle is defined by the internal clock of the control unit. The Pentium based systems have a clock speed of 1GHz or more whereas 3 years ago the speed used to be 300 MHz. The bus carries data, control signals, and address in a system. If the data bus width is same as the word length, then one word can be moved at a time. If the bus width is half of word length, two cycles are required for moving one word. The instruction set also affects the speed. If the instruction set is simple, as in RISC, one or more 8 Computer For Managers instructions may get executed in each cycle. There will be some long instructions, which take more than one cycle. It is possible that a given application extensively uses long instructions (such as scientific computing) and the machine will appear to be slow. There is no direct relationship between clock frequency and the speed of a system. There are benchmark programs that are run to establish the speed of a computer system. 1.5 STORAGE AND STORAGE DEVICES The large amount of data is stored on a computer using various types of storage media. The storage media are distinguished by their relative speed, capacity, and resilience to failure. 1) Volatile Storage: Information residing in such storage needs continuous power supply. The contents are lost if power supply is switched off. Examples of such storage devices are main memory and cache memory, which we will discuss in the next section. Access to volatile storage is very fast, both because of the technology used and because of the access method. 2) Nonvolatile Storage: The nonvolatile storage media do not require power supply to retain their contents. Examples of such storage media are disks and magnetic tapes. Disk is used for online storage, while tapes are used for archival storage. Disks and magnetic tapes are very reliable storage media. The current technology used for nonvolatile storage makes them much slower than volatile storage. 1.5.1 Main Memory Main memory holds the programs and data required by the CPU for carrying out its operations. The primary storage is a semiconductor device that is built using integrated circuits. The data is stored in binary form by main memory. Numeric as well as non-numeric data can be represented in binary form. With two binary digits, we can represent 4 different characters. With three binary digits, we can represent 8 different characters. Computes internally use eight binary digits to represent characters and digits (A binary digit is referred to as bit and 8 bits are called a byte). 256 characters can be represented by a byte. The main memory consists of many thousands of bytes. The table given below lists commonly used names, abbreviations and the number of bytes for storage capacity. Table 1.1: Commonly Used Names and Abbreviations for Storage Capacity Name Abbreviation Number of Bytes Byte B 1 Kilobyte KB 1,024 Megabyte MB 1,024 * 1,024 (about one million) Gigabyte GB 1,024 * 1,024 * 1,024 Terabyte TB 1,024 * 1,024 * 1,024 * 1,024 Computers For Managers 9 1.5.2 COMPUTER MEMORY A computer is an electronic device and that accepts data, processes on that data, and gives the desired output. It performs programmed computation with accuracy and speed. Or in other words, the computer takes data as input and stores the data/instructions in the memory (use them when required). After processes the data, it converts into information. Finally, gives the output. Here, input refers to the raw data that we want the machine to process and return to us as a result, output refers to the response that the machine provides in response to the raw data entered and the processing of data may involve analyzing, searching, distributing, storing data, etc. Thus, we can also call a computer data processing system. What is Computer Memory? Computer memory is just like the human brain. It is used to store data/information and instructions. It is a data storage unit or a data storage device where data is to be processed and instructions required for processing are stored. It can store both the input and output can be stored here. Characteristics of Computer Memory It is faster computer memory as compared to secondary memory. It is semiconductor memories. It is usually a volatile memory, and main memory of the computer. A computer system cannot run without primary memory. How Does Computer Memory Work? When you open a program, it is loaded from secondary memory into primary memory. Because there are various types of memory and storage, an example would be moving a program from a solid-state drive (SSD) to RAM. Because primary storage is accessed more quickly, the opened software can connect with the computer’s processor more quickly. The primary memory is readily accessible from temporary memory slots or other storage sites. Memory is volatile, which means that data is only kept temporarily in memory. Data saved in volatile memory is automatically destroyed when a computing device is turned off. When you save a file, it is sent to secondary memory for storage. There are various kinds of memory accessible. It’s operation will depend upon the type of primary memory used. but normally, semiconductor-based memory is more related with memory. Semiconductor memory made up of IC(integrated circuits) with silicon- based metal- oxide-semiconductor (MOS) transistors. Types of Computer Memory In general, computer memory is of three types: Primary memory Secondary memory Cache memory 10 Computer For Managers  Now we discuss each type of memory one by one in detail: 1. Primary Memory It is also known as the main memory of the computer system. It is used to store data and programs or instructions during computer operations. It uses semiconductor technology and hence is commonly called semiconductor memory. Primary memory is of two types: a) 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. RAM is of two types: S RAM (Static RAM): S RAM 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. D RAM (Dynamic RAM): D RAM 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 S RAM. b) 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: 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. 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. 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. EEPROM (Electrically Erasable Programmable Read Only Memory): Here the written contents can be erased electrically. You can delete and reprogramme 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. 2. Secondary Memory It is also known as auxiliary memory and backup memory. It is a non-volatile memory and used to store a large amount of data or information. The data or information stored in secondary memory is permanent, and it is slower than primary memory. A CPU cannot access secondary memory directly. The data/information from the auxiliary memory is first transferred to the Computers For Managers 11 main memory, and then the CPU can access it. Characteristics of Secondary Memory It is a slow memory but reusable. It is a reliable and non-volatile memory. It is cheaper than primary memory. The storage capacity of secondary memory is large. A computer system can run without secondary memory. In secondary memory, data is stored permanently even when the power is off. Types of Secondary Memory 1. Magnetic Storage Magnetic storage devices store data using magnetic fields to represent binary data (0s and 1s). It has been one of the most commonly used forms of secondary storage for decades due to its affordability and large storage capacity. a. Hard Disk Drive (HDD): Description: HDDs are the most common magnetic storage devices. They consist of a spinning disk coated with magnetic material, with a read/write head that moves across the disk surface to read or write data. Capacity: Typically ranging from 500 GB to several TB. Speed: Slower compared to solid-state drives (SSDs), with speeds measured in revolutions per minute (RPM). Common RPMs are 5400 or 7200 RPM. Usage: Used for everyday storage of files, software, and operating systems in desktops and laptops. b. Magnetic Tape: Description: Magnetic tape is a long, narrow strip of plastic film with a thin, magnetic coating on it that is used for magnetic recording. Bits are recorded on tape as magnetic patches called RECORDS that run along many tracks. Typically, 7 or 9 bits are recorded concurrently. Each track has one read/write head, which allows data to be recorded and read as a sequence of characters. It can be stopped, started moving forward or backward, or rewound. Magnetic tape is a sequential storage device used primarily for large-scale backup and archival purposes. Data is stored in a linear format on a long strip of tape. Capacity: Modern tapes can store several TBs of data. Speed: Slower than HDDs and not suitable for random access, as the tape must be wound to the correct location before data can be read or written. Usage: Mostly used for data backup, archiving, and disaster recovery in businesses and data centers. 2. Optical Storage 12 Computer For Managers Optical storage devices use lasers to read and write data on discs, which are coated with reflective materials. Optical storage is slower and less frequently used today, though it still serves as an inexpensive medium for distribution and long-term archiving. a. CD (Compact Disc): Description: CDs are optical storage media that use a laser to read and write data. They are generally used to store music, software, and smaller amounts of data. Capacity: Approximately 700 MB. Types: CD-ROM: Read-only, used for distributing software and media. CD-R: Recordable, allows data to be written once. CD-RW: Rewritable, allows data to be written multiple times. b. DVD (Digital Versatile Disc): Description: DVDs are similar to CDs but can store much more data, often used for movies, software, and games. Capacity: Around 4.7 GB for single-layer discs and up to 8.5 GB for dual-layer discs. Types: DVD-ROM: Read-only. DVD-R/DVD+R: Recordable, allows one-time data writing. DVD-RW/DVD+RW: Rewritable. 3. Solid-State Storage Solid-state storage devices use integrated circuits (ICs) to store data, offering faster data access speeds and greater reliability than magnetic or optical storage because they have no moving parts. Solid-state storage has become increasingly popular for secondary storage due to its high speed and durability. a. Solid-State Drive (SSD): Description: SSDs are data storage devices that use NAND flash memory to store data. Unlike HDDs, they have no moving parts, making them much faster and more reliable. Capacity: Typically ranging from 120 GB to several TB. Speed: Much faster than HDDs, with significantly lower access times and higher read/write speeds. Usage: Commonly used in modern laptops, desktops, and servers for operating systems, applications, and files. b. USB Flash Drive (Pen Drive or Thumb Drive): Description: A small, portable solid-state storage device that plugs into a computer’s USB port. It is widely used for transferring files between devices. Computers For Managers 13 Capacity: Typically, from 2 GB to 512 GB or more. Speed: Varies, but generally slower than SSDs. Usage: Used for data transfer, backups, and temporary storage. c. Memory Card (SD Card): Description: Small, portable solid-state storage devices used primarily in cameras, smartphones, and other portable devices. Capacity: Typically ranging from 2 GB to 1 TB. Usage: Commonly used in cameras, mobile phones, tablets, and gaming consoles. 3. Cache Memory Cache memory is a specialized type of high-speed memory that acts as a buffer between the CPU and the main memory (RAM) in a computer system. It is designed to store copies of data or instructions that are frequently accessed by the CPU, allowing for quicker data retrieval and significantly improving the overall performance of the system. Here’s a more detailed explanation of cache memory and how it functions: What is Cache Memory? Cache memory is faster than the main memory (RAM) but is much smaller in size. It is used to temporarily store data that the CPU frequently uses. The reason cache is used is that fetching data from RAM can be relatively slow compared to the speed at which modern CPUs operate. The CPU performs billions of instructions per second, and if it had to access RAM for every piece of data or instruction, it would slow down. To avoid this, cache memory provides quick access to the most relevant and frequently used data and instructions, reducing the time it takes for the CPU to retrieve the necessary information. Why is Cache Memory Important? Cache memory bridges the speed gap between the CPU and RAM. The CPU works at much higher clock speeds than RAM, and without a cache, the CPU would have to wait for slower memory access from the RAM. By storing frequently used data closer to the CPU in the cache, the CPU can work more efficiently. The key advantages of cache memory include: Speed: Cache memory is much faster than RAM, which is why it can supply the CPU with data at the speed it requires. Efficiency: By storing the most frequently used data and instructions, the CPU reduces the need to access slower main memory, which enhances performance. Reduced Latency: Cache minimizes the delay (latency) in data fetching, enabling the CPU to process instructions faster. 14 Computer For Managers  It keeps the programs that can be run in a short amount of time. It stores data in temporary use. Types of Cache Memory Cache memory is usually divided into levels, with each level having different speed and size characteristics: a) L1 (Level 1) Cache: Location: Built directly into the processor chip. Size: Smallest cache, typically ranging from 16KB to 128KB. Speed: Fastest cache, operating at the same speed as the CPU. Function: Stores critical data and instructions that the CPU is likely to need next. Each core in a multi-core processor typically has its own L1 cache. b) L2 (Level 2) Cache: Location: Either on the processor chip or very close to it. Size: Larger than L1 cache, typically from 256KB to a few MB. Speed: Slower than L1 but still much faster than RAM. Function: Acts as a backup for L1 cache, storing data and instructions that are used less frequently but still important. It is shared by multiple cores in some CPUs. c) L3 (Level 3) Cache: Location: Often shared between all cores of the CPU. Size: Significantly larger than L1 and L2, typically ranging from a few MB to tens of MB. Speed: Slower than L2 cache but faster than RAM. Function: Acts as a final layer before data is retrieved from the main memory. It is used to store data that is not needed as frequently as L1 or L2 data. Disadvantages of Cache Memory Because of the semiconductors used, it is very expensive. The size of the cache (amount of data it can store) is usually small. Computers For Managers 15 1.6 CLASSIFICATION OF COMPUTERS The computer putting on the desk in the classroom is a microcomputer. It is a small, powerful piece of equipment. Even so, the power of the microcomputer is not enough for most large organizations. The computer industry consists of more than just microcomputers. Any classification of computers is somewhat arbitrary. Traditionally, computers have been classified by their size, processing speed and cost. This section explores four commonly used classifications: 1.6.1) Classification on the basis of size: 1) Supercomputers These are the largest, fastest, most powerful and most expensive computers made. Supercomputers can be accessed by many individuals at the same time. Supercomputers are used primarily for scientific applications that are mathematically intensive. The aerospace, automotive, chemical, electronics and petroleum industries use supercomputers extensively. Supercomputers are used in weather forecasting and seismic analysis. These are found in many public and private research centers, such as universities and government laboratories. A supercomputer was used to alert scientists to the impending collision of a comet with Jupiter in 1994, giving them time to prepare to observe and record the event. The United States Department of Energy recently contracted with IBM for an 'ultra-supercomputer,' three hundred times faster than any existing machine. The ultra-supercomputer will simulate nuclear explosions (eliminating the need to detonate any bombs), model global weather trends and design power plants. Supercomputers derive much of their speed from the use of multiple processors. Multiprocessing enables the computers to perform tasks simultaneously-either assigning different tasks to each processing unit or dividing a complex task among several processing units. The first supercomputer had four central processing units; the massively parallel processors of today contain hundreds of processors. The speed of modern supercomputers is measured in nanoseconds and gigaflops. A nanosecond is one billionth of a second. A gigaflop is one billion floating-point arithmetic operations per second. Supercomputers can perform at upto 128 gigaflops and use bus widths of 32 or 64 bits. This capability makes supercomputers suitable for processor-intensive applications, such as graphics. Supercomputers are rarely used for input/output-intensive processing, such as accounting or record-keeping operations. 16 Computer For Managers 2) Mainframes For input/output-intensive operations, mainframe computers are much more suitable than supercomputers. Many modern mainframes have multiprocessing capabilities; however, these are generally limited to eight or fewer processors. The processors in mainframes are slower than those in supercomputers, with speed measured in megaflops (millions of floating-point arithmetic operations per second) rather than gigaflops. A mainframe computer system is usually composed of several computers in addition to the mainframe or host processor, as shown in Fig. 1.6.1. The host processor is responsible for controlling the other processors, all the peripheral devices and Fig. 1.6.1: Mainframes the mathematics operations. A front-end processor is responsible for handling communications to and from all the remote terminals connected to the computer system. Sometimes a backend processor is used to handle data retrieval operations. Although the host computer could perform all these operations, it can be used more efficiently if relieved of time-consuming chores that do not require processing speed. Fig. 1.6.2 depicts this relationship. Fig. 1.6.2: Relationship between front-end processor, back-end processor and host Mainframe computer systems are powerful enough to support several hundred users simultaneously at remote terminals. Terminals can be located near the computer or miles away. Computers can support hundreds of users by keeping numerous programs in primary memory and rapidly switching back and forth between programs. Because computers are so much faster than people, the users never notice that the computer is handling other tasks. This capability to process multiple programs concurrently for multiple users is known as multiprogramming. The introduction of the microcomputer and the increased capabilities of minicomputers have resulted in a decline of sales of mainframe computers. Recently, to booster sales of mainframes, IBM started producing mainframes based on arrays of microprocessor chips and designed to be servers for giant databases used on networks of microcomputers. 3 ) Minicomputers The major difference between mainframes and minicomputers is in scale. Minicomputers can perform the same types of tasks as mainframes, but minicomputers are a little slower. Like mainframes, minicomputers can accommodate remote users, but not as many. Minicomputers’ input, output and Computers For Managers 17 storage devices look like those on mainframes; but minicomputers have slightly less storage and the printers are slightly slower. The distinctions between these categories of computers are blurring as time passes. Minicomputers are frequently referred to as mid-range computers. 4) Workstations and Microcomputers When we are working on a multi-user computer, such as a mainframe or a minicomputer, we can control the input and see the output on the display, but we control nothing else. A single-user computer gives us control over all the phases of computer processing: input, processing, output and storage. We can select the programs we want to use and we don’t have to compete with other users to gain access to the system. A single-user system is designed to meet the computing needs of an individual. Single-user computers fall into two categories: workstations and microcomputers. (a) Workstations: This is a powerful desktop computer designed to meet the computing needs of engineers, architects and other professionals who need detailed graphics displays. For example, workstations are commonly used for Computer-Aided Design (CAD), in which industrial designers create pictures of technical parts or assemblies. To process these complex and detailed diagrams, the computer needs much processing power and storage. Workstations are also frequently used as servers for local area networks. The workstation has sometimes been called a 'supermicro.' The workstation looks very much like a desktop microcomputer, but the chips inside make the difference. Most workstations use Reduced Instruction Set Computer (RISC) microprocessors. Computer designers have discovered that by eliminating infrequently used pre-programmed instructions, the speed of the processor can be increased. Many new processor chips, including the DEC Alpha and the PowerPC, are RISC chips. RISC processors are particularly useful in special-purpose applications, such as graphics, in which speed is critical. The DEC Alpha chip was the first microprocessor designed to work with a 64-bit bus. (b) Microcomputers: A microcomputer is a small, relatively inexpensive computer designed for individual use. Unlike larger computer systems like mainframes and minicomputers, microcomputers are built around a microprocessor as the central processing unit (CPU), which is responsible for executing instructions and managing tasks. Microcomputers are what most people commonly think of when they refer to personal computers (PCs). They are versatile devices used for a variety of tasks such as word processing, gaming, internet browsing, multimedia, and business applications. Fig 1.6.3 Fig. 1.6.3: Laptop 18 Computer For Managers 1.6.2) Classifications on the basis of Purpose: 1) General-Purpose Computers General-purpose computers are versatile machines designed to perform a wide range of tasks. They can run various types of software applications, allowing users to carry out multiple activities, such as word processing, browsing the internet, playing games, and much more. Features: Flexibility: General-purpose computers can be programmed to perform different tasks by installing different software applications. User-Friendly: They typically come with operating systems (like Windows, macOS, or Linux) that provide a user-friendly interface. Wide Range of Applications: Suitable for various functions including education, business, entertainment, and research. Hardware Components: Equipped with standard hardware components like a CPU, RAM, storage devices (HDD/SSD), input devices (keyboard, mouse), and output devices (monitor, printer). Examples: Personal Computers (PCs): Used in homes and offices for general computing tasks. Laptops: Portable computers used for similar purposes as desktops but with the added convenience of mobility. Tablets: Touchscreen devices used for browsing, media consumption, and basic computing tasks. Smartphones: Highly portable devices that function like computers with the ability to run various applications. Applications: Education: Used for online learning, research, and assignments. Business: Used for document creation, spreadsheets, presentations, and communication (emails). Entertainment: Used for gaming, streaming videos, and social media. Research: Used for data analysis, simulations, and programming. 2. Special-Purpose Computers Special-purpose computers are designed to perform specific tasks or functions. Unlike general-purpose computers, they are optimized for a particular job and cannot be easily programmed to perform different tasks. Features: Task-Specific Design: Built to handle particular applications efficiently, which makes them faster and more efficient for those specific tasks. Limited Functionality: They do not have the flexibility of general-purpose computers and cannot run arbitrary software. Computers For Managers 19  Integrated Systems: Often include dedicated hardware and software tailored for the task they are designed for. Reliability and Consistency: Designed for long-term operation without failures, often in critical environments. Examples: Embedded Systems: These are special-purpose computers integrated into devices to control specific functions. Examples include: o Microwave Ovens: Control cooking time and temperature. o Washing Machines: Manage wash cycles and water levels. o Cars: Control engine management systems, braking systems, and navigation. ATMs (Automated Teller Machines): Designed to perform banking transactions like cash withdrawal, deposits, and balance inquiries. Traffic Control Systems: Manage and monitor traffic signals and flow in urban areas. Medical Devices: Such as MRI machines, which have specific functions to perform medical imaging. Applications: Automotive: Used in engine control units (ECUs) and safety systems. Home Appliances: Control the operation of appliances like refrigerators, dishwashers, and air conditioning systems. Industrial Automation: Used in manufacturing for process control, robotics, and assembly lines. Telecommunications: Used in routers and switches for data management. 1.6.3) Classifications on the basis of Type: Computers can be classified based on their functioning and data processing methods into three main types: Analog Computers, Digital Computers, and Hybrid Computers. Here’s a detailed overview of each type, including their features, examples, applications, and distinctions. 1. Analog Computers Analog computers are devices that process continuous data. They represent information in physical quantities such as voltage, current, mechanical motion, etc. Instead of using discrete values (like digital computers), analog computers work with a range of values to perform calculations. Features: Continuous Data Processing: They handle real-time data and can represent changes smoothly over a continuous range. High-Speed Operation: Capable of performing complex calculations quickly due to their continuous nature. Specific Functionality: Often designed for specialized tasks and typically do not use standard programming languages. 20 Computer For Managers  Examples: Slide Rule: A mechanical analog device used for mathematical calculations. Oscilloscope: A device that displays waveforms and signals, showing changes over time. Flight Simulators: Used to simulate real-life flying conditions by processing continuous variables like altitude and speed. Applications: Engineering: Used for simulating and analyzing dynamic systems like control systems in aircraft. Weather Forecasting: Used in modeling meteorological data and predicting weather patterns. Signal Processing: Commonly used in audio and video equipment for manipulating signals. 2. Digital Computers Digital computers process discrete data, using binary digits (0s and 1s) to represent and manipulate information. They are the most commonly used type of computers today, capable of executing complex computations, running various applications, and performing a wide range of tasks. Features: Binary Data Processing: Operate using binary number systems, which makes them reliable for performing calculations and processing information. Programmability: Capable of running various software applications, allowing for flexibility and versatility. High Precision: Provide accurate results due to the precise nature of binary arithmetic. Examples: Personal Computers: Desktops and laptops used for everyday computing tasks. Smartphones: Handheld devices that combine communication and computing functions. Servers: High-performance computers designed to manage network resources and handle large data loads. Applications: Business: Used for data management, word processing, spreadsheets, and presentations. Education: Employed in online learning platforms, research, and teaching tools. Entertainment: Used for gaming, streaming, and multimedia production. 3. Hybrid Computers Computers For Managers 21  Hybrid computers combine features of both analog and digital computers, allowing them to process both continuous and discrete data. They leverage the advantages of both types to perform specialized tasks more effectively. Features: Versatility: Can handle a wide range of applications due to their ability to process different types of data. Integration: Often used in systems where both real-time data processing (analog) and high- precision calculations (digital) are needed. Complex Functionality: Capable of executing tasks that require both analog and digital processing. Examples: Medical Equipment: Devices like ECG machines that monitor heart activity (analog) and store patient data (digital). Industrial Control Systems: Systems that control processes in manufacturing, integrating real-time data with computerized control mechanisms. Weather Stations: Devices that collect continuous environmental data (analog) and analyze it digitally. Applications: Aerospace: Used in aircraft navigation systems that require both continuous tracking (analog) and discrete data analysis (digital). Medical Monitoring: Employed in hospitals to monitor patients' vital signs and provide real-time data analysis. Research and Development: Used in laboratories for experiments that require simultaneous analog and digital data processing. 22 Computer For Managers  Computer Concepts 1.7 HISTORICAL PERSPECTIVE Generations of Computer: The modern computer took its shape with the arrival of your time. It had been around the 16th century when the evolution of the computer started. The initial computer faced many changes, obviously for the betterment. It continuously improved itself in terms of speed, accuracy, size, and price to urge the form of the fashionable day computer. Basic Terms Related to Computers The basic terms related to generations of computers are listed below. Vacuum Tube: Vacuum tubes have the functionality of controlling the flow of electronics in a vacuum. Generally, it is used in switches, amplifiers, radios, televisions, etc. Transistor: A transistor helps in controlling the flow of electricity in devices, it works as an amplifier or a switch. Integrated Circuit (IC): Integrated circuits are silicon chips that contain their circuit elements like transistors, resistors, etc. Microprocessors: Microprocessors are the components that contain the CPU and its circuits and are present in the Integrated Circuit. Central Processing Unit (CPU): The CPU is called the brain of the computer. CPU performs processing and operations work. Magnetic Drum: Magnetic Drum is like a cylinder that stores data and cylinder. Magnetic Core: Magnetic cores are used to store information. These are arrays of small rings. Machine Language: Machine Language is the language that a computer accepts (in the form of binary digits). It is also called low-level programming language. Memory: Memory is used to store data, information, and program in a computer. Artificial Intelligence: Artificial Intelligence deals with creating intelligent machines and behaviors. Phases of Computer Generations This long period is often conveniently divided into the subsequent phases called computer generations. First Generation Computers (1940-1956) Second Generation Computers (1956-1963) Third Generation Computers (1964-1971) Fourth Generation Computers (1971-Present) Fifth Generation Computers (Present and Beyond) List of Five Generations of Computers The journey of five generations of computers begins with vacuum tube circuitry from the 1940s and goes beyond the methods and approaches of artificial intelligence (AI) to the present day. These are as follows: First Generation Computers By 1940, vacuum tubes, electronic devices that regulate the flow of electrons in a vacuum, were Computer For Managers 23  used. These were the first computer systems that the users utilized for circuitry and magnetic drums and were usually massive, capturing up an entire room. These computers were very costly to operate in the spare of employing a great deal of electricity. At that time, the most common computer language that the first-generation computers depended on was the machine language, the lowest-level programming language that the computers understood for executing operations. The UNIVAC and ENIAC computers are specimens of first-generation computing devices. Characteristics of First-Generation Computers The main electronic component of first-generation computers is the vacuum tubes. It operated in machine language. Its primary memories were the Magnetic tapes and magnetic drums. It employed input/output devices like paper tape and punched cards. Second Generation Computers In 1956, the technology of transistors replaced the bulkier generation of vacuum tubes. After the invention of these transistors, the dimensions of the computer were also reduced. Second- generation computers evolved smaller in size compared to first-generation computers. Second-generation computers developed from enigmatic binary machine language to representational symbolic systems, or assembly languages, that authorized the programmers to appoint instructions in words or phrases. IBM1400 series, PDP-8, IBM 7090 and 7094, UNIVAC 1107, CDC 3600, etc., are a few examples of the second generation. Characteristics of Second-Generation Computers The main electronic component of second-generation computers is electronic transistors. It operated in Machine language and assembly language. Its primary memories were the Magnetic core and magnetic tape or magnetic disk. Its Input/output devices were the Magnetic tape and punched cards. Third Generation Computers This generation started developing integrated circuits in 1964. Instead of using punch cards and printouts, users could interact with third-generation computers via keyboards and monitors and interfaced with an operating system. For the first time, computers reached a mass audience, as they were smaller and cheaper than the past prototypes. Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor developed integrated circuits by 1950. Characteristics of Third-Generation Computers The main electronic component of third-generation computers is integrated circuits. It operated in High-level language. Its primary memories were the large magnetic core and magnetic tape/disk. Its Input/output devices were the Magnetic tape, monitor, keyboard, printer, etc. 24 Computer For Managers  Computer Concepts Fourth Generation Computers By 1971, users operated the first microprocessors, the Large-Scale Integration (LSI) circuits created on one chip called microprocessors. The microprocessor was conducted in the fourth generation of computers, as developers-built thousands of integrated circuits onto a single silicon chip. What if the first generation served an entire room that could accommodate within a palm? The Intel 4004 chip, developed in 1971, located all the computer components from the Central Processing Unit and memory to input or output authorities on a single chip. Characteristics of Fourth-Generation Computers The main electronic components of fourth-generation computers are very large-scale integration (VLSI) and the microprocessor (VLSI contains thousands of transistors inside a single microchip). It operated in High-level language. Its primary memory was the semiconductor memory (mainly RAM, ROM, etc.) Its Input/output devices were the pointing devices, optical scanning, keyboard, monitor, printer, etc. Fifth Generation Computers The technology on which the fifth generation of computers relies is AI. It authorizes computers to conduct like humans. Today's computers are so developed that users utilize them in every distinct field, primarily accounting, constructing buildings, space research, engineering technologies, and other types of analysis. The principal purpose of fifth-generation computing is to create devices that react to natural language input and are competent in learning and self- organizing. Characteristics of Fifth-Generation Computers The main electronic components of fourth-generation computers are ultra-large-scale integration (ULSI) and the parallel processing technique. It operated in natural human language. Its Input/output devices were the Trackpad, touch screen, pen, speech input, light scanner, etc. The human drive to learn required innovations in equipments. Past inventions made future innovations possible innovations, from graphics capabilities to parallel processing, have filtered down from the supercomputers to the mainframes. We can foresee the future of small computers by watching the developments in the larger machines. Various renovations along with important points (at a glance) are given in the Table 1.7.1, which is as follows: Computer For Managers 25  Generation Years Circuitry Characterized by First 1951 to 1959 Vacuum tubes Magnetic drum and magnetic tape; difficult to program; used machine language and assembly language Second 1959 to 1963 Transistors Magnetic cores and magnetic disk, used high-level languages and were easier to program Third 1963 to 1975 Integrated circuit Minicomputer accessible by multiple users from remote terminals Fourth 1975 to present VLSI The Personal computer and user-friendly micro-programs; very fast processor chip high-level language; Object Oriented Programming (OOP) Fifth Present to ULSI, Parallel Handheld PCs, iPad, Biomatrix Devices, Generation Future Processing, AI, Note book, Ultra book etc. More Quantum userfriendly interface with multimedia Computing, features. Nenotechnology Table 1.7.1: Generations of Computers 1.8 FUNCTIONS OF CPU The CPU carries out instructions and tells the rest of the computer system 'what to do'. This is done by the Control Unit of the CPU which sends command signals to the other components of the system, as shown in Fig. 1.8.1. Fig. 1.8.1: Components of CPU ⚫ It also performs arithmetic calculations and data manipulation, e.g. comparisons, sorting, 26 Computer For Managers  Computer Concepts combining, etc. This is performed by a part of the CPU known as the Arithmetic Logic Unit. ⚫ It holds data and instructions which are in current use. These are kept in the Main Store or Memory. Fig. 1.8.1 shows 'how the whole system works', It shows the basic components of a generalized CPU. An actual CPU may have these components or other with different names that provide the same functions. 1.8.1) Control Unit The control unit directs the entire computer system to carry out stored program instructions. The control unit must communicate with both the arithmetic logic unit and main memory. The control unit uses the instruction contained in the Instruction Register to decide which circuits need to be activated. Fig. 1.8.2 presents a structural view of CU. The control unit co- ordinates the activities of the other two units as well as all peripheral and auxiliary storage devices linked to the computer. The control unit instructs the arithmetic logic unit which arithmetic operations or logical operation is to be performed. Fig. 1.8.2: Structural View of CU Specialised electronic circuitry in the control unit is designed to decode program instructions held in the main memory. Each instruction is read from the memory into the instruction register. The process of reading an instruction, is often referred to as the fetch-execute process. The Program Counter (PC), also known as the Instruction Pointer (IP) in some architectures, is a crucial register within the Central Processing Unit (CPU) of a computer. Its primary function is to hold the address of the next instruction to be executed in a program. 1.8.2) Arithmetic Logic Unit The Arithmetic and Logical Unit (ALU) is a critical part of a computer's Central Processing Unit (CPU), responsible for performing all mathematical and logical operations. It handles arithmetic tasks like addition, subtraction, multiplication, and division, and also performs logical operations like comparing values using AND, OR, NOT, and XOR functions. Essentially, whenever a computer needs to make a calculation or a decision based on logic (such as comparing two numbers), the ALU is where this work happens. Computer For Managers 27  The ALU receives input from the CPU, which includes the numbers (operands) to be processed and a command specifying which operation to perform. After processing, the result is sent back to the CPU, where it can either be used for further computations or stored in memory. Additionally, the ALU uses flags to report certain conditions (like if a result is zero or if an operation caused an overflow). These flags help the CPU make decisions based on the outcomes of operations. In short, the ALU is the computational brain of the computer, enabling it to process data and make decisions that allow software and applications to run efficiently. Without the ALU, computers would not be able to perform even the simplest calculations or logical comparisons. 1.8.3) Memory Unit The Memory Unit is the part of the computer that holds data and instructions for processing. Although it is closely associated with the CPU, but in actual fact, it is separate. Memory associated with the CPU is also called primary storage, primary memory, main storage, internal storage and main memory. When we load software from a floppy disk, hard disk or CD-ROM, it is stored in the Main Memory. It’s amazing 'how many different types of electronic memory encounter in daily life.' Many of them have become an integral part of the vocabulary: RAM, ROM, Cache, Dynamic RAM, Static RAM, Flash memory, Memory sticks, Volatile memory, Virtual memory, Video memory, BIOS. We already know that computer has memory. What we may not know, is that most of the electronic items, we use every day, have some form of memory also. Here are just a few examples of the many items that use memory: Computers, Cell phones, Personal Digital Assistants (PDAs), Game consoles, Car radios, VCRs, TVs. Each of these devices uses different types of memory in different ways. There are two basic types of computer memory inside the computer, RAM and ROM. (a) Random Access Memory (RAM): This is really the main store and is the place where the programs and software we load gets stored. When the Central Processing Unit runs a program, it fetches the program instructions from the RAM and carries them out. If the Central Processing Unit needs to store the results of calculations, it can store them in RAM. A sample picture of the RAM is given is Fig. 1.8.4. RAM can have instructions READ from it by the CPU and also it can have numbers or other computer data WRITTEN to it by the CPU. When we switch a computer off, whatever is stored in the RAM gets erased. 28 Computer For Managers  Computer Concepts Fig. 1.8.3: RAM RAM is the best-known form of computer memory. RAM is considered 'random access' because anyone can access any memory cell directly if we know the row and column that intersect at that cell. The opposite of RAM is Serial Access Memory (SAM). SAM stores data as a series of memory cells that can only be accessed sequentially (like a cassette tape). If the data is not in the current location, each memory cell is checked until the needed data is found. SAM works very well for memory buffers, where the data is normally stored in the order in which it will be used (a good example is the texture buffer memory on a video card). RAM data, on the other hand, can be accessed in any order. (b) Read Only Memory (ROM): The CPU can only fetch or read instructions from Read Only Memory (or ROM). ROM comes with instructions permanently stored inside and these instructions cannot be over-written by the computer’s CPU. ROM is used for storing special sets of instructions which the computer needs when it starts up. When we switch the computer off, the contents of the ROM do not get erased but remain stored permanently. Therefore, it is non-volatile. Read-only memory (ROM), also known as firmware, is an integrated circuit programmed with specific data when it is manufactured. ROM chips are used not only in Central computers, but in most other Processing electronic items as well. Unit Fig. 1.8. 4 s h o ws the relationship between the ROM Central Processing Unit and the Main Memory (RAM and ROM). Fig. 1.8.4: Relationship between CPU and Main Memory Computer For Managers 29 (c) Cache Memory: Caching is a technology based on the memory subsystem of the computer. The main purpose of a cache is to accelerate the computer while keeping the price of the computer low. Caching allows to do the computer tasks more rapidly. Cache technology is the use of a faster but smaller memory type to accelerate a slower but larger memory type. When using a cache, we must check the cache to see if an item is in there. If it is there, it’s called a cache hit. If not, it is called a cache miss and the computer must wait for a round trip from the larger, slower memory area. A cache has some maximum size that is much smaller than the larger storage area. It is possible to have multiple layers of cache. There are a lot of subsystems in a computer; one can put cache between many of them to improve performance. Here’s an example. We have the microprocessor (the fastest thing in the computer). Then there’s the L1 cache that caches the L2 cache that caches the main memory which can be used (and is often used) as a cache for even slower peripherals like hard disks and CD-ROMs. The hard disks are also used to cache an even slower medium — Internet connection. A list of different types of cache is given as follows: ⚫ L1 cache - Memory accesses at full microprocessor speed (10 nanoseconds, 4 kilobytes to 16 kilobytes in size) ⚫ L2 cache - Memory access of type SRAM (around 20 to 30 nanoseconds, 128 kilobytes to 512 kilobytes in size) ⚫ Main memory - Memory access of type RAM (around 60 nanoseconds, 32 megabytes to 128 megabytes in size) ⚫ Hard disk - Mechanical, slow (around 12 milliseconds, 1 gigabyte to 10 gigabytes in size) (d) Flash Memory: Electronic memory comes in a variety of forms to serve a variety of purposes. Flash memory is used for easy and fast information storage in such devices as digital cameras and home video game consoles. It is used more as a hard drive than as RAM. In fact, Flash memory is considered a solid-state storage device. Solid state means that there are no moving parts — everything is electronic instead of mechanical. Here are a few examples of Flash memory: ⚫ Computer’s BIOS chip ⚫ CompactFlash (most often found in digital cameras) ⚫ SmartMedia (most often found in digital cameras) ⚫ Memory Stick (most often found in digital cameras) ⚫ PCMCIA Type I and Type II memory cards (used as solid-state disks in laptops) ⚫ Memory cards for video game consoles 1.9 VIRTUAL MEMORY Most computers today have something like 32 or 64 megabytes of RAM available for the CPU to use. Unfortunately, that amount of RAM is not enough to run all of the programs that most users expect to run at once. For example, if we load the operating system, an e-mail program, a Web browser and word processor into RAM simultaneously, 32 megabytes is not enough to hold it all. If there were no such thing as virtual memory, then once we filled up the available RAM, our computer would have to say, “Sorry, you cannot load any more applications. Please close another application to load a new one.” With virtual memory, what the computer can do is look at RAM for areas that have not been used recently and copy them onto the hard disk. This frees up space in RAM to load the new application. A hierarchy of memories is given in Fig. 1.9.1. 30 Computer For Managers  Computer Concepts CPU Register Cache Level 1 Level 2 Storage RAM Physical RAM Virtual Memory Storage Device Types ROM/ Removable Network/ Hard Storage BIOS Drives Internet Drive Storage Input Sources Scanner/ Camera/ Remote Keyboard Mouse Removable Other Mic/ Source Media Sources Video Fig. 1.9.1: Hierarchy of Memory Because this copying happens automatically, we don’t even know it is happening and it makes our computer feel like that it has unlimited RAM space even though it only has 32 megabytes installed. Because hard disk space is so much cheaper than RAM chips, it also has a nice economic benefit. The read/write speed of a hard drive is much slower than RAM and the technology of a hard drive is not geared toward accessing small pieces of data at a time. If our system has to rely too heavily on virtual memory, we will notice a significant performance drop. The key is to have enough RAM to handle everything we tend to work on simultaneously — then, the only time we “feel” the slowness of virtual memory is when there’s a slight pause when we are changing tasks. When that’s the case, virtual memory is perfect. When it is not the case, the operating system has to constantly swap information back and forth between RAM and the hard disk. This is called thrashing and it can make our computer feel incredibly slow. The area of the hard disk that stores the RAM image is called a page file. It holds pages of RAM on the hard disk and the operating system moves data back and forth between the page file and RAM. On a Windows machine, page files have a SWP extension. Computer For Managers 31  2 C Computer Fundamentals H INPUT/OUTPUT AND A P AUXILIARY STORAGE T E DEVICES R LEARNING OBJECTIVES ⚫ To know about various input devices like keyboard, mouse, trackball etc. ⚫ To discuss about various output devices like moniter, printer etc. ⚫ To understand the classification of moniter, printer etc. 2.1 INPUT DEVICES An input device is any machine that feeds data into a computer. For example, a keyboard is an input device. Input devices other than the keyboard are sometimes called alternate devices. Trackballs and light pens are all alternate input devices. 2.1.1 Keyboard Keyboard is an input device; consisting of a set of typewriter-like keys that enables to enter data into a computer as shown in Fig. 2.1.1. Computer keyboards are similar to electric-typewriter keyboards but contain additional keys. The keys on computer keyboards are often classified as follows: ⚫ Alphanumeric Keys - letters and numbers ⚫ Punctuation Keys - comma, period, semicolon and so on. ⚫ Special Keys - function keys, control keys, arrow keys, Caps Lock key and so on. The standard layout of letters, numbers and punctuation is known as a QWERTY keyboard because the first five keys on the top row of letters spell QWERTY. The QWERTY keyboard was designed in the 1800s for mechanical typewriters and was Fig. 2.1.1: Keyboard actually, designed to slow typists down to avoid jamming the keys. Another keyboard design, which has letters positioned for speed typing, is the Dvorak keyboard. There is no standard computer keyboard, although many manufacturers imitate the standards of 22 Computer For Managers  Input/Output PCs. There are actually three different PC standards: the original PC keyboard, with 84 keys; the AT keyboard, also with 84 keys; and the enhanced keyboard, with 101 keys. The three differ somewhat in placement of function keys, the Control key, the Return key and the Shift keys. In addition to these keys, IBM keyboards contain the following Keys: Page Up, Page Down, Home, End, Insert, Pause, Num Lock, Scroll Lock, Break, Caps- Lock, Print Screen. Many companies have developed ergonomic keyboards, which reduce the strain while typing with the aim to prevent stress related injuries. Microsoft’s natural keyboard is one example. 2.1.2 Mouse Mouse is a device that controls the movement of the cursor or pointer on a display screen, as shown in Fig. 2.1.2. A mouse is a small object that can roll along a hard flat surface. Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to be the mouse’s tail and the fact that one must make it scurry along a surface. As we move the mouse, the pointer on the display screen moves in the same direction. Mouse contains at least one button and sometimes as many as three, which have different functions depending on what program is running. Now- a-days, mouse is connected with computer through USB port. Invented by Douglas Engelbart of Stanford Research Fig. 2.1.2: Mouse Center in 1963 and pioneered by Xerox in the 1970s, the mouse is one of the great breakthroughs in computer ergonomics because it frees the user to a large extent from using the keyboard. In particular, the mouse is important for graphical user interfaces because one can simply point to options and objects and click a mouse button. Such applications are often called point-and-click programs. T17 mouse is also useful for graphics programs that allows to draw pictures by using the mouse like a pen, pencil or paintbrush. Types of Mouse: There are three basic types of Mouse: ⚫ Mechanical: It has a rubber or metal ball on its underside that can roll in all directions. Mechanical sensors within the mouse detect the direction the ball is rolling and move the screen pointer accordingly. ⚫ Optomechanical: It is same as a mechanical mouse, but uses optical sensors to detect motion of the ball. ⚫ Optical: It does a laser to detect the mouse’s movement. One must move the mouse along a special mat with a grid so that the optical mechanism has a frame of reference. Optical mice Fig. 2.1.3: Trackball have no mechanical moving parts. They respond more quickly and precisely than mechanical and optomechanical mice, but they are also more expensive. Computer For Managers 23 2.1.4 Trackball This is another pointing device. Essentially, a trackball is a mouse lying on its back. To move the pointer, we rotate the ball with our thumb, our fingers or the palm of our hand. There are usually one to three buttons next to the ball, which we use just like mouse buttons. The advantage of trackballs over mice is that the trackball is stationary so it does not require much space to use it. In addition, we can place a trackball on any type of surface, including our lap. For both these reasons, trackballs are popular pointing devices for portable computers. 2.1.5 Joystick With a joystick, the pointer continues moving in the direction the joystick is pointing. To stop the pointer, we must return the joystick to its upright position. Most joysticks include two buttons called triggers. It has a lever that moves in all directions and controls the movement of a pointer or some other display symbols. A joystick is similar to a mouse, except that with a mouse the cursor stops moving as soon as we stop moving the mouse. Joysticks are used mostly for computer games, but they are also used occasionally for CAD/ CAM systems and other Fig. 2.1.4: Joystick applications. 2.1.6 Digitizing Tablet This is an input device that enables to enter drawings and sketches into a computer. A digitizing tablet consists of an electronic tablet and a cursor or pen. A cursor (also called a puck) is similar to a mouse, except that it has a window with cross hairs for pinpoint placement and it can have as many as 16 buttons. A pen (also called a stylus), which looks like a simple ballpoint pen but uses an electronic head instead of ink. The tablet contains electronics that enable it to detect movement of the cursor or pen and translate the movements into digital signals that it sends to the computer. Fig. 2.1.5: Digitizing Tablet For digitizing tablets, each point on the tablet represents a point on the display screen in a fixed manner. This differs from mice, in which all movement is relative to the current cursor position. The static nature of digitizing tablets makes them particularly effective for tracing drawings. Most modern digitizing tablets also support a mouse emulation mode, in which the pen or cursor acts like a mouse. Digitizing tablets are also called digitizers, graphics tablets, touch tablets or simply tablets. 2.1.7 Scanners Scanner is an input device that can read text or illustrations printed on paper and translate the information into a form that the computer can use. A scanner works by digitizing an image - dividing it into a grid of boxes and representing Fig. 2.1.6: Scanner each box with either a zero or a one, depending on whether 24 Computer For Managers  Use Of Computers the box is filled in. (For color and gray scaling, the same principle applies, but each box is then represented by up to 24 bits.) The resulting matrix of bits, called a bit map, can then be stored in a file, displayed on a screen and manipulated by programs. Optical scanners do not distinguish text from illustrations; they represent all images as bit maps. Therefore, we cannot directly edit text that has been scanned. To edit text read by an optical scanner, we need an Optical Character Recognition (OCR) system to translate the image into ASCII characters. Most optical scanners sold today come with OCR packages. Scanners differ from one another in the following respects: ⚫ Scanning Technology: Most scanners use Charge-Coupled Device (CCD) arrays, which consist of tightly packed rows of light receptors that can detect variations in light intensity and frequency. The quality of the CCD array is probably the single most important factor affecting the quality of the scanner. Industry- strength drum scanners use a different technology that relies on a Photo Multiplier Tube (PMT), but this type of scanner is much more expensive than the more common CCD -based scanners. ⚫ Resolution: The denser the bit map, the higher the resolution. Typically, scanners support resolutions from 72 to 600 Dots Per Inch (DPI). Fig. 2.1.7: CCD Based Scanner ⚫ Bit depth: The number of bits used to represent each pixel. The greater the bit depth, the more colors or grayscales can be represented. For example, a 24-bit color scanner can represent 2 to the 24th power (16.7 million) colors. However, a large color range is useless if the CCD arrays are capable of detecting only a small number of distinct colors. ⚫ Size and shape: Some scanners are small hand-held devices that can be moved across the paper. These hand-held scanners are often called half-page scanners because they can only scan 2 to 5 inches at a time. Hand-held scanners are adequate for small pictures and photos, but they are difficult to use if we need to scan an entire page of text or graphics. Larger scanners include machines into which we can feed sheets of paper. These are called sheet-fed scanners. These are excellent for loose sheets of paper, but they are unable to handle bound documents. A second type of large scanner, called a flatbed scanner, is like a photocopy machine. It consists of a board on which we lay books, magazines and other documents that we want to scan. 2.1.8 Digital Camera Images can be input into a computer using a digital camera. These images can then be manipulated in many ways using the various imaging tools available. The digital camera takes a still photograph, stores it and then sends it as digital input into the computer. The images are then stored as digital files. 2.1.9 Magnetic Ink Character Recognition (MICR) Fig. 2.1.8: Digital Camera This allows the computer to recognize characters printed using magnetic ink. MICR is a direct-entry method used in banks. This technology is used to automatically read those frustrating-looking numbers on the bottom of the cheque. A special-purpose machine known Computer For Managers 25 as a reader/sorter reads characters made of ink containing magnetized particles. A related technology is the magnetic strip, used on the back of credit cards and bank debit cards, that allows readers such as Automated Teller Machines (ATMs) to read account information and facilitate monetary transactions. Another example of magnetic strip technology is in ID cards, which can be used for a variety of functions from attendance monitoring to restricting access to specific locations. 2.1.10 Optical Character Recognition (OCR) It refers to the branch of computer science that involves reading text from paper and translating the images into a form that the computer can manipulate (for example, into ASCII codes). An OCR system enables to take a book or a magazine article and feed it directly into an electronic computer file. All OCR systems include an optical scanner for reading text and a sophisticated software for analyzing images. Most OCR systems use a combination of hardware (specialized circuit boards) and software to recognize characters, although some inexpensive systems do it entirely through software. Advanced OCR systems can read text in a large variety of fonts, but they still have difficulty with handwritten text. The potential of OCR systems is enormous because they enable users to harness the power of computers to access printed documents. OCR is already being used widely in the legal profession, where searches that once required hours or days can now be accomplished in a few seconds. 2.1.11 Optical Mark Recognition (OMR) OMR also called mark sensing, is a technology where an OMR device senses the presence or absence of a mark, such as a pencil mark. OMR is used in tests such as aptitude tests for different competition/entrance examinations. 2.1.12 Bar Code Reader Fig. 2.1.9: Bar Code Reader Most of the persons are probably familiar with the bar code readers in supermarkets, bookshops etc. Bar-code readers are photoelectric scanners that read the bar codes or vertical zebra striped marks, printed on product containers. Supermarkets use a bar code system called the Universal Product Code (UPC). The bar code identifies the product to the supermarket’s computer, which has a description and the latest price of the product. The computer automatically tells the Point of Sales (POS) terminal what the price is. 2.1.13 Speech Input Devices Speech or voice input devices convert a person’s speech into digital form. These input devices, when combined with appropriate software, form voice recognition systems. These systems enable users to operate microcomputers using voice commands. Fig. 2.1.10: Speech Input Device 26 Computer For Managers  Use Of Computers Some of these systems must be ‘trained’ to the particular user’s voice. This is done by his/her spoken words to patterns previously stored in the computer. More advanced systems that can recognize the same word spoken by many different people have been developed. However, until recently the list of words has been limited. A newly developed voice recognition system like IBM VoiceType identifies more than 30,000 words and adapts to individual voices. There are even systems that translate from one language to another, such as from English to Japanese. There are two types of voice recognition systems: ⚫ Continuous speech: These systems are used to control a microcomputer’s operations and to issue commands to special application programs. For example, rather than using the keyword to save a spreadsheet file, the user could simply say 'Save the file'. Two popular systems are Apple Computer’s PlainTalk and IBM’s continuous speech series. ⚫ Discrete-Word: A common activity in business is preparing memos and other written documents. Discrete-word recognition systems allow users to dictate directly into a microcomputer using a microphone. The microcomputer stores the memo in a word processing file where it can be revised later or directly printed out. IBM Voice Type Simply Speaking is an example. 2.1.14 Touch Screen Touch screen is a type of display screen that has a touch sensitive transparent panel covering the screen. Instead of using a pointing device such as a mouse or light pen, we can use our finger to point directly to objects on the screen. Although touch screens provide a natural interface for computer novices, they are unsatisfactory for most because the finger is such a relatively large object. It is impossible to point accurately to small areas of the screen. In addition, most usersfind touch-screens tiring to the arms after long use. 2.1.15 Touch Pad It is a small, touch-sensitive pad used as a pointing device on some portable computers. By moving a finger or other object along the pad, one can move the pointer on the screen. Fig. 2.1.11: Touch Screen 2.1.16 Light Pen Light Pen is an input device that utilizes a light-sensitive detector to select objects on a display screen. A light Pen is similar to a mouse, except that with a light pen we can move the pointer and select objects on a display screen by directly pointing to the objects by light pen. 2.1.17 Biometrics When referring to computers and security, biometrics is the identification of a person by the measurement of their biological features. For example, a user identifying themselves to a computer or building by their finger print or voice is considered biometrics identification. When compared to a password, this type of system is much more difficult to fake since it is unique to the person. Below is a listing of some known biometric devices. Fig. 2.1.12: Biometrics Computer For Managers 27 Other common methods of a biometrics scan are a person's face, hand, iris and retina. Types of biometric devices Face scanner - Biometric face scanners identify a person by taking measurements of a person face. For example, the distance between the persons chin, eyes, nose and mouth. These types of scanners can be very secure assuming they are smart enough to distinguish between a picture of a person and a real person. Hand scanner - Like your finger print, the palm of your hand is also unique to you. A biometric hand scanner will identify the person by the palm of their hand. Finger scanner - A biometric finger scanner identifies the person by their finger print. These can be a secure method of identifying a person, however, cheap and less sophisticated finger print scanners can be duped a number of ways. For example, in the show Myth Busters they were able to fake a finger print using a Gummy Bear candy treat. Retina or iris scanner - A biometric retina or iris scanner identifies a person by scanning the iris or retina of their eyes. These scanners are more secure biometric authentication schemes when compared to the other devices because there is no known way to duplicate the retina or iris. Voice scanner - Finally, a voice analysis scanner will mathematically break down a person's voice to identify them. These scanners can help improve security but with some less sophisticated scanners can be bypassed using a tape recording. 2.1.18 Graphics tablet Alternatively referred to as a drawing tablet and pen tablet, a graphics tablet is a highly accurate hardware input device that Fig. 2.1.13: Graphics tablet enables an artist to draw or sketch easier than they would be able to do with a standard computer mouse. 2.1.19 Light gun A light gun is a pointing input device that detects light using a photodiode in the gun barrel. When the player of the game pulls the trigger