AnnaUniversity First Year Unit I



General-purpose computer – the electronic chips contain programs that allow the user to perform a range of complex processes and calculations.

Computer is an electronic device which capable of solving problems and manipulating data.  A general-purpose computer is defined as an electronic device that:

·        operates under the control of a set of instructions, called a program, that is stored in its memory

·        accepts data supplied by a user

·        manipulates the data according to the programmed instructions

·        produces the results (information)

·        stores the results (information) for future use

A computer is an electronic device, operating under the control of instructions stored in its own memory, that can accept data (input), process the data according to specified rules (process), produce results (output), and store the results (storage) for future use


The Information Processing Cycle


Using a computer to convert data into useful information is referred to as information processing (also called data processing). Processing data into information involves four basic functions:


·        input – data entered into a computer for processing

·        processing – the manipulation of data according to program instructions

·        output – the creation of information resulting from processing

·        storage – the retention of processed data on a storage medium for future use


Collectively, these steps are known as the information processing cycle.


Characteristics of Computers


 Computers operate with lightening-like speed, and processing speeds are increasing as new and improved models are introduced.

Contemporary personal computers are capable of executing billions of instructions per second and larger computers,

such as supercomputers, can execute trillions of instructions per second.


 Computers are extremely accurate when accurate programs and data are entered and processed correctly. The popular expression garbage-in, garbage-out (GIGO) means that if inaccurate programs and data are entered into a computer for processing, the resulting output will also be inaccurate.


  • A computer is a lack of concentration.
  • It can work for hours without creating any error
  • Due to this capability it overpowers human being in routine type of work.


 Computers are perhaps the most versatile of all machines or devices. They can perform a variety of personal, business, and scientific applications. Computers are frequently used by families, banks, retailers, manufacturers, schools, government agencies, hospitals, and scientific organizations for a variety of useful and important applications.


 A computer is capable of accepting and storing programs and data. Computers can store huge amounts of data and, once stored in a computer, users can access programs and data again and again to process different data.

 Power of Remembering

 n       Any amount of information can be stored in computer and recalled as long as you require it, for any numbers of years.

n       It depends entirely upon you how much data you want to store in a computer and when to lose or retrieve these data.

 No Feeling

n       It does not have feelings ,

n       it does not get tired even after long hours of work.

 No IQ (intelligence quotient)

n       Computer is a dumb machine and it cannot do any work without instruction from the user and it cannot take its own decision as you can


 Most modern computers contain special equipment and programs that allow them to communicate with other computers through telephone lines, cable connections, and satellites. Computers having this capability are often linked together so users can share programs, data, information, and equipment such as a printer. The structure in which computers are linked together is called a network

 Evolution of Computers

 The abacus was an early aid for mathematical computations. Its only value is that it aids the memory of the human performing the calculation. A skilled abacus operator can work on addition and subtraction problems at the speed of a person equipped with a hand calculator (multiplication and division are slower). The abacus is often wrongly attributed to China. In fact, the oldest surviving abacus was used in 300 B.C. by the Babylonians. The abacus is still in use today, principally in the Far East.

 In 1617 an eccentric Scotsman named John Napier invented logarithms, which are a technology that allows multiplication to be performed via addition. The magic ingredient is the logarithm of each operand, which was originally obtained from a printed table. But Napier also invented an alternative to tables, where the logarithm values were carved on ivory sticks which are now called Napier’s Bones.

Napier’s invention led directly to the slide rule, first built in England in 1632 and still in use in the 1960’s by the NASA engineers of the Mercury, Gemini, and Apollo programs which landed men on the moon.

Leonardo da Vinci (1452-1519) made drawings of gear-driven calculating machines but apparently never built any.

The first gear-driven calculating machine to actually be built was probably the calculating clock, so named by its inventor, the German professor Wilhelm Schickard in 1623. This device got little publicity because Schickard died soon afterward in the bubonic plague.

In 1642 Blaise Pascal, at age 19, invented the Pascaline as an aid for his father who was a tax collector. Pascal built 50 of this gear-driven one-function calculator (it could only add) but couldn’t sell many because of their exorbitant cost and because they really weren’t that accurate (at that time it was not possible to fabricate gears with the required precision).

Just a few years after Pascal, the German Gottfried Wilhelm Leibniz (co-inventor with Newton of calculus) managed to build a four-function (addition, subtraction, multiplication, and division) calculator that he called the stepped reckoner

 In 1801 the Frenchman Joseph Marie Jacquard invented a power loom that could base its weave (and hence the design on the fabric) upon a pattern automatically read from punched wooden cards, held together in a long row by rope. Descendents of these punched cards have been in use ever since

 By 1822 the English mathematician Charles Babbage was proposing a steam driven calculating machine the size of a room, which he called the Difference Engine. This machine would be able to compute tables of numbers, such as logarithm tables. He obtained government funding for this project due to the importance of numeric tables in ocean navigation.

 And by then was on to his next brainstorm, which he called the Analytic Engine. This device, large as a house and powered by 6 steam engines, would be more general purpose in nature because it would be programmable, thanks to the punched card technology of Jacquard. But it was Babbage who made an important intellectual leap regarding the punched cards.

 Hollerith’s invention, known as the Hollerith desk, consisted of a card reader which sensed the holes in the cards, a gear driven mechanism which could count

Hollerith built a company, the Tabulating Machine Company which, after a few buyouts, eventually became International Business Machines, known today as IBM.

 Mark I computer which was built as a partnership between Harvard and IBM in 1944. This was the first programmable digital computer made in the U.S. But it was not a purely electronic computer. Instead the Mark I was constructed out of switches, relays, rotating shafts, and clutches. The machine weighed 5 tons, incorporated 500 miles of wire, was 8 feet tall and 51 feet long, and had a 50 ft rotating shaft running its length, turned by a 5 horsepower electric motor. The Mark I ran non-stop for 15 years,

 ENIAC, which stood for Electronic Numerical Integrator and Calculator. ENIAC was built at the University of Pennsylvania between 1943 and 1945 by two professors, John Mauchly and the 24 year old J. Presper Eckert


Once ENIAC was finished and proved worthy of the cost of its development, its designers set about to eliminate the obnoxious fact that reprogramming the computer required a physical modification of all the patch cords and switches. It took days to change ENIAC’s program. Eckert and Mauchly’s next teamed up with the mathematician John von Neumann to design EDVAC, which pioneered the stored program. Because he was the first to publish a description of this new computer

By the end of the 1950’s computers were no longer one-of-a-kind hand built devices owned only by universities and government research labs. Eckert and Mauchly left the University of Pennsylvania over a dispute about who owned the patents for their invention. They decided to set up their own company. Their first product was the famous UNIVAC computer, the first commercial (that is, mass produced) computer. In the 50’s, UNIVAC (a contraction of “Universal Automatic Computer”) was the household word for “computer” just as “Kleenex” is for “tissue”. The first UNIVAC was sold, appropriately enough, to the Census bureau. UNIVAC was also the first computer to employ magnetic tape.

 A microprocessor (uP) is a computer that is fabricated on an integrated circuit (IC). Computers had been around for 20 years before the first microprocessor was developed at Intel in 1971.

 1642 – Blaise Pascal invents mechanical calculator (counting device)

1830- Charles’s Babbages “Difference Engine”

            First Steam-powered “Analytical Engine”

1880’s- John H. Patterson’s Mechanical cash register (NCR)

            First applications for computing devices

1930’s- Claude Shannon: Suggests use of Binary system for use with electronic circuits

1940s- John Von Neumann:Proposes reconfigurable computing by storing programs in                                                    memory

1940s – 1950s: First electronic computers,

    • Vacuum tubes & mechanical relays: UNIVAC, ENIAC
    • 30 tons
    • 150KWatt
    • 80 bytes of memory

ILLIAC (Metze et. al. play Illinois fight song on accumulator bit. – first computer music)

1948- John Bardeen, Walter Brattain, William Schockley file patent on invention of the transistor

1958- Jack Kilby: introduces concept of “Integrated Circuit”

1960s- Computers begin to use transistors.

1965- Gordon Moore

  • Observes that every chip produced contained roughly twice as much capacity as its predecessor and that chips new generations of chips were being released every 18-24 months.

Late 1960s- IBM mainframes

  • Powerful, centralized CPUs with terminals
  • Age of the “big iron”

1970s- DEC PDP-11s

  • Low-cost Mini-computers
  • Age of the “Vaxen”

1974- Microprocessors

  • Intel introduces the 8080 (a “toy”)
  • Bill Gates sophmore year at Harvard

1974- Altair 8800

    • 8080 CPU
    • Affordable ($379 kit)
    • No screen (LEDs on front panel)
    • No keyboard (DIP switches on front panel)
    • No storage
    • 4k memory.
  • Bill Gates & Paul Allen start writing BASIC

1977- Apple II, Commodore-64

1980- IBM meets with Bill Gates to license BASIC/MSDOS (QDOS)

1981- IBM Personal Computer:

  • 16-bit microprocessor: 4.77 MHz 8088
  • cassette interface,
  • 360k floppy (optional)
  • DOS 1.0

1982- Illiac-IV

1983- Low cost computing

    • 10 MByte Hard disk costs $3000
    • 640KB of Memory costs $1000
  • Compaq introduces “Portable Computing”

1984- Macintosh: GUI based on work at Xerox Parc

  • IBM Introduces PC-AT: 80286-based system.
  • Record year for IBM.
  • Lockwood buys first 8088 computer.

1985- First 32-bit 80×86 CPUs

  • Intel introduces 80386
  • Address up to 4 Gbytes of memory.

1986- First 32-bit 80×86 Systems

  • Compaq introduces first 80386-based system

1989- Intel introduces 80486, includes math co-processor (FPU)

1992- AMD/Cyrix 486 (Compatible CPUs)
Intel Pentium (64-bit memory bus)

1996- Use of Reduced Instruction Set Computer (RISC) core to exectute 80×86 instructions

    • AMD K5 (RISC Ops = ROPS)
    • Intel Pentium Pro
  • Superscalar Execution
    • AMD K5/K6
    • Cyrix M1 (6×86)
    • Intel Pentium Pro
  • Powerful, Entry-level systems
    • 100 MIP CPUs
    • 32M DRAM
    • 12x CDROM

1997- Single Instruction Multiple Data (SIMD):
Multimedia Extensions / Matrix Math Extensions (MMX)

    • AMD K6,
    • Intel Pentium-II
    • Cyrix/IBM M2 (6×86 MX)
  • Low-Cost computing:
    • 233 Mhz CPU w/MMX: $300
    • 64MB of Memory: $300 (300 times cheaper/MB than 1983 !)

1998- Single Instruction Multiple Data (SIMD) for Floating Point operations

    • AMD K6-2 w/3DNow
  • Integrated CPU/Video/Audio:
    • Cyrix/NSM MediaGX
  • Low-Cost computing:
    • 300 MHz CPU w/MMX+3D: $125
    • 64 MB of Memory (PC-100 SDRAM): $75
    • 10 GByte Hard Drive: $200

1999+- More Floating point Parallelism

    • Pentium III (Katmai)
  • Faster Bus Architectures
    • AMD K3-III (3DNow + 256k on-chip Full-speed L2 cache)
    • AMD K7 (Fast Alpha EV-6 Bus)
  • Explicit Instruction-level Floating-point Parallelism:
    • Merced IA-64 (80×86/PA-RISC)
    • Supercomputing on the Microprocessor
  • Ubiquitous Computing
  • Active Networks

Computer Generations

1-First Generation Computers

n      First generation computers used Thermion valves. These computers were large in size and writing programs on them was difficult.

n       Some of the computers of this generation were:

   ENIAC : It was named Electronic Numerical Integrator And Calculator (ENIAC). Today your favorite computer is many times as powerful as ENIAC, still size is very small.

   EDVAC: It stands for Electronic Discrete Variable Automatic Computer and was developed in 1950. The advantages is storing and doing logical decision internally.

n      Other Important Computers of First Generation:

 EDSAC: ( Electronic Delay Storage Automatic Computer )



Limitations of First Generation Computer:

·      The operating speed was quite slow.

·       Power consumption was very high.

·       It required large space for installation.

·       The programming capability was quite low.

2-Second Generation Computers

  • Around 1955 a device called Transistor replaced the bulky electric tubes in the first generation computer. They have no filament and require no heating. Manufacturing cost was also very low. Thus the size of the computer got reduced considerably.
  • It is in the second generation that the concept of Central Processing Unit (CPU), memory, programming language and input and output units were developed. The programming languages such as COBOL, FORTRAN were developed during this period. Some of the computers of the Second Generation were:
  • IBM 1620: Its size was smaller as compared to First Generation computers and mostly used for scientific purpose.
  • IBM 1401: Its size was small to medium and used for business applications.
  • CDC 3600: Its size was large and is used for scientific purposes.

3 Third Generation Computers

 was introduced in 1964. They used Integrated Circuits (ICs). Some of the computers developed during this period were: IBM-360, ICL-1900, IBM-370, and VAX-750.

  •  Higher level language such as BASIC    was developed during this period.
  • Computers of this generations were small in size, low cost, large memory and processing speed is very high.

4-Fourth Generation Computers( present day computers) .

 It uses large scale Integrated Circuits (LSIC) built on a single silicon chip called microprocessors. Due to the development of microprocessor it is possible to place computer’s central processing unit (CPU) on single chip. These computers are called microcomputers.

5-Fifth Generation Computer

was introduced  in 1990s . The speed is extremely high and it can perform parallel processing. The concept of Artificial intelligence has been introduced to allow the computer to take its own decision. It is still in a developmental stage.

 Classification of Computers

 Analog computer:

 Digital computer:


Microcomputer is at the lowest end of the computer range in terms of speed and storage capacity. Its CPU is a microprocessor. The most common application of personal computers (PC) is in this category. The PC supports a number of input and output devices. Examples of microcomputer are IBM PC, PC-AT


q     1973: Xerox Alto

q     1975: Altair

q     1978: Apple II

q     1981: IBM PC (5150)

q     1983: Apple Macintosh


2-Mini Computer.

n      The mini computer is used in multi-user system in which various users can work at the same time. This type of computer is generally used for processing large volume of data in an organization. They are also used as servers in Local Area Networks (LAN).


n      These types of computers are generally 32-bit microprocessors. They operate at very high speed, have very large storage capacity and can handle the work load of many users. They are generally used in centralized databases. They are also used as controlling nodes in Wide Area Networks (WAN).

n      Example of mainframes are DEC, ICL and IBM 3000 series.


They are the fastest and most expensive machines. They have high processing speed compared to other computers. They have also multiprocessing technique. One of the ways in which supercomputers are built is by interconnecting hundreds of microprocessors.

n      Supercomputers are mainly being used for whether forecasting, biomedical research, remote sensing, aircraft design and other areas of science and technology. Examples of supercomputers are CRAY YMP, CRAY2, NEC SX-3, CRAY XMP and PARAM from India.

 Categories of Computers

 Rapid advances in computer technology often blur the differences among types of computers, and industry professionals may disagree on how computers should be categorized. Typically, they use criteria based on differences in usage, size, speed, processing capabilities, and price, resulting in the following categories. For an overview, see Table 1-1.

 Personal Computers

A personal computer (PC) is a self-contained computer capable of input, processing, output, and storage. A personal computer is designed to be a single-user computer and must have at least one input device, one output device, a processor, and memory. The three major groups of PCs are desktop computers, portable computers, and handheld computers.

 Desktop Computers A desktop computer is a PC designed to allow the system unit, input devices, output devices, and other connected devices to fit on top of, beside, or under a user’s desk or table. This type of computer may be used in the home, a home office, a library, or a corporate setting.

 Portable Computers A portable computer is a PC small enough to be moved around easily. As the name suggests, a laptop computer fits comfortably on the lap. As laptop computers have decreased in size, this type of computer is now more commonly referred to as a notebook computer. Manufacturers recently began introducing a new type of computer called the tablet PC, which has a liquid crystal display (LCD) screen on which the user can write using a special-purpose pen, or stylus. Tablet PCs rely on digital ink technology that allows the user to write on the screen. Another type of portable computer, called a wearable computer, is worn somewhere on the body, thereby providing a user with access to mobile computing capabilities and information via the Internet.

 Did You Know? In 1974, Micro Instrumentation Telemetry Systems (MITS) began selling the Altair personal computer, widely regarded as the world’s first PC, as a mail-order kit. Buyers were required to assemble the components.

 Handheld Computers An even smaller type of personal computer that can fit into the hand is known as a handheld computer (also called simply handheld, pocket PC, or Palmtop). In recent years, a type of handheld computer called a personal digital assistant (PDA) has become widely used for performing calculations, keeping track of schedules, making appointments, and writing memos. Some handheld computers are Internet-enabled, meaning they can access the Internet without wire connections. For example, a smartphone is a cell phone that connects to the Internet to allow users to transmit and receive e-mail messages, send text messages and pictures, and browse through Web sites on the phone display screen.


 A workstation is a high-performance single-user computer with advanced input, output, and storage components that can be networked with other workstations and larger computers. Workstations are typically used for complex applications that require considerable computing power and high-quality graphics resolution, such as computer-aided design (CAD), computer-assisted manufacturing (CAM), desktop publishing, and software development.

 Midrange Servers

 Linked computers and terminals are typically connected to a larger and more powerful computer called a network server, sometimes referred to as a host computer. Although the size and capacity of network servers vary considerably, most are midrange rather than large mainframe computers (discussed later).

 Ø      Midrange server – formerly known as a minicomputer, a midrange server is a powerful computer capable of accommodating hundreds of client computers or terminals (users) at the same time.

 Ø      Terminal – a device consisting of only a monitor and keyboard, with no processing capability of its own.

 Mainframe Computers

 Larger, more powerful, and more expensive than midrange servers, a mainframe computer is capable of accommodating hundreds of network users performing different computing tasks. These computers are useful for dealing with large, ever-changing collections of data that can be accessed by many users simultaneously. Government agencies, banks, universities, and insurance companies use mainframes to handle millions of transactions each day.


 A supercomputer is the fastest, most powerful, and most expensive of all computers. Many are capable of performing trillions of calculations in a single second. Primary applications include weather forecasting, comparing DNA sequences, creating artificially intelligent robots, and performing financial analyses.

Did You Know? The fastest computer in the world is IBM’s latest supercomputer, named the BlueGene/L. Housed at the Lawrence Livermore National Laboratory, it can perform up to 280.6 trillion calculations in one second. The next system, Blue Gene/P, scheduled for completion in 2008, is expected to have a processing speed of 1 quadrillion calculations per second.

Basic Computer organization






Storage Unit

      Control Unit

     Memory Unit


Data Flow

 Instruction flow


Computer Hardware: An Overview

 Hardware includes all of the physical components that comprise the computer and other devices connected to it, such as the keyboard or monitor. These connected devices are referred to as peripheral devices because they are outside, or peripheral to, the computer.

Hardware devices are grouped into the following categories:


  • system unit
  • input devices
  • output devices
  • storage devices
  • communications devices

 The System Unit The system unit is a relatively small plastic or metal cabinet housing the electronic components that process data into information. Inside the cabinet is the main circuit board, called the motherboard (Figure 1-7), which provides for the installation and connection of other electronic components. The main components of the motherboard include:


  • central processing unit (CPU), also called the processor, which consists of electronic chips that read, interpret, and execute the instructions that operate the computer and perform specific computing tasks.
  • memory, also called primary storage, which consists of small electronic chips that provide temporary storage for instructions and data during processing.

 Input Devices An input device is a hardware device that allows users to enter program instructions, data, and commands into a computer. Common input devices are the keyboard, mouse, and microphone.

 Output Devices An output device is a device that makes information available to the user. Some output devices produce output in hardcopy (tangible) form, while other output devices produce output in softcopy (intangible) form that can be viewed, but not physically handled.

 Storage Devices Unlike memory that stores instructions and data temporarily during processing, a storage device, often called secondary storage, provides for the permanent storage of programs, data, and information that can be reused.

 Communications Devices A communications device makes it possible for a user to communicate with another computer and to exchange instructions, data, and information with other computer users. The most popular communications device is a modem, an electronic device capable of converting computer-readable information into a form that communications systems, such as standard telephone lines, can transmit and receive.

 The Central Processing Unit

 Every computer contains a central processing unit (CPU). The CPU of larger computers often spans several separate microprocessor chips and various circuit boards, whereas in a personal computer the CPU is a single chip. This microprocessor chip is a small electronic device consisting of tiny transistors and other circuit parts on a piece of semiconductor material.

 Recall from Chapter 1 that the CPU, or microprocessor, is often referred to as the “brain” of a personal computer system because it interprets and executes the instructions for most computer operations. The CPU consists of a control unit, an arithmetic/logic unit (ALU), and registers (see Figure 2-13).

 These components of the CPU perform four basic operations that are collectively called a machine cycle. The machine cycle includes fetching an instruction, decoding the instruction, executing the instruction, and storing the result (see Figure 2-14). The machine cycle is the same for all types of computers.

 Did You Know? Intel’s first microprocessor, the 4004, was introduced in 1971. It contained 2,300 transistors. Today’s Pentium 4 processor, by contrast, contains 55 million transistors.

 Control Unit The control unit directs and coordinates the overall operation of the computer system. It acts as a traffic officer, signaling to other parts of the computer system what they are to do. It interprets program instructions and then initiates the action needed to carry them out. These are the fetching and decoding steps of the machine cycle. Fetching means retrieving an instruction or data from memory. Decoding means interpreting or translating the instruction into strings of binary digits (bytes) the computer understands. The time required to fetch and decode an instruction is called instruction time, or I-time.

 Arithmetic/Logic Unit The arithmetic/logic unit (ALU) is the part of the CPU that performs the executing step of the machine cycle. Executing means carrying out the instructions and performing arithmetic and logical operations on the data. The arithmetic operations the ALU can perform are addition, subtraction, multiplication, and division. The ALU can also perform logical operations, such as comparing data items.

 Registers To speed up processing, the ALU uses registers (temporary storage locations) to hold instructions and data. This is the storing step of the machine cycle. Storing means writing or recording the result to memory. The time required to execute and store an instruction is called execution time, or E-time.

 Various kinds of registers are used, each serving a specific purpose. Once processing begins, an instruction register holds instructions currently being executed. A data register holds the data items being acted upon. A storage register hold the immediate and final results of processing.


Number Systems 

 Binary to Decimal


        Multiply each bit by 2n, where n is the “weight” of the bit

        The weight is the position of the bit, starting from 0 on the right

        Add the results

1010112 =>     1 x 20 = 1
                        1 x 21 = 2
                        0 x 22 = 0
                        1 x 23 = 8
                        0 x 24 = 0
                        1 x 25 =32


Octal to Decimal


        Multiply each bit by 8n, where n is the “weight” of the bit

        The weight is the position of the bit, starting from 0 on the right

        Add the results

7248 =>           4 x 80 =              4
                        2 x 81 =             16
                        7 x 82 =            448

Hexadecimal to Decimal



        Multiply each bit by 16n, where n is the “weight” of the bit

        The weight is the position of the bit, starting from 0 on the right

        Add the results

ABC16 =>        C x 160 = 12 x   1 =   12
                        B x 161 = 11 x 16 = 176
                        A x 162 = 10 x 256 = 2560


Decimal to Binary


        Divide by two, keep track of the remainder

        First remainder is bit 0 (LSB, least-significant bit)

        Second remainder is bit 1


12510 =? 2

12510 = 11111012


Octal to Binary



        Convert each octal digit to a 3-bit equivalent binary representation

Hexadecimal to Binary



        Convert each hexadecimal digit to a 4-bit equivalent binary representation

         Convert a hexadecimal number to a binary number,

         simply divided  the binary number into 4-bit groups

         Substitute the corresponding four bits in binary for each hexadecimal digit in the number.

         For example,  convert ABCD to a binary value, The binary equivalent is:

          ABCD= 1010 1011 1100 1101


Binary to Octal


        Group bits in threes, starting on right

        Convert to octal digits

Binary to Hexadecimal


        Group bits in fours, starting on right

        Convert to hexadecimal digits

         Binary to Hex Conversion

         Break the binary number into 4-bit groups from the Left to the right.

         Convert the 4-bit binary number to its Hex equivalent.

         For example, the binary value 101011111011 0010 will be written:

         1010 1111 1011 0010=AFB2










































































  1. November 12, 2008 at 6:50 AM

    Sir yu r jus MIND BLOWING .. its a superb website sir.. i wish yu publish some important ques too wen the unit tests comes

  2. Divya Venkat
    January 28, 2010 at 2:40 AM

    Thanx a lot….!!!!!!!!! i prepared for my semester oly wit yur notes as i did not purchase a book………… thanx again 🙂

  3. iswariya
    December 10, 2010 at 3:08 AM

    I want design and anlysi question bank with answers…

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