Lecture 1

Book Title: Fundamental concepts of computer system

By: Asiya Sultan Ali

Amena Nudrat

Lecture 1Dated: 17,18 Oct,2011

By: Ms Saira Jabeen

What is Computer?

• Computer is a device or set of devices which work according to the instruction (programs) given to it, It accepts the data process (manipulate) it to produce the output information

• Accept the data: (Voice, video, Data)• Process it: (performs mathematical and/or

logical operations)• Produce the information (Either on screen or on

paper as In hard form)

Characteristics of a Computer

• Fast, reliable

• Can receive , process and store information or produce output

• Programs wide range of tasks, easily quickly and effectively

Comparison between actions taken by computer and human being

• Computer• Store program in

internal memory • Reads data in

machine readable form and stores in internal/external memory

• Perform arithmetic operations

• Human being• Remember the

instructions • Reads data in written

or printed form and memories it or files it

• Perform arithmetic operations

Comparison between actions taken by computer and human being

• Make decision• Retrieves data from

internal/external memory

• Output the data on output device

• Make decision• Remembers data or

retrieves data from files

• Writes or speaks the results

Data

• Data is the collection of raw and unorganized material , that can be organized to produce meaningful information (to solve the problems)

• Data can be in form of voice , Video, Data (Alphabetical, Numerical, Alphanumeric, special characters)

• Examples: Different pulses of voice are ordered together to get meaningful information, e.g every individual alphabet in the statement has its own meaning but when we combine these words together it becomes a meaningful information, “We are in the class”

Data

• Different slides of images are combined together to make a meaningful documentary or movie.

• The marks of different subjects are compiled on a single transcript, which becomes a meaningful information

Information

• Information is the accurate and processed data, upon which necessary actions are taken to make the decision.

• Example: Bill, library cards (every student is given the library card, which contains the processed accurate data i.e. student name, class, semester etc. when this card is shown to the librarian he takes the actions)

Historical background

• Computers did not appear on the scene suddenly, even in centauries back there were need of calculating and manipulating devices, so the research since than till today brought today’s full fledge computer to our steps in every field around us.

• The history of computer starts from, 3000 BC: Abacus used for performing calculation, abacus consists of number of strings contains numbers of beads


• 1617: John Napier introduced first calculating device. Consisted of numbered rods. This made long calculations faster.

• 1642: Pascal invented first mechanical calculator, the number 0-9 were marked on wheels which were calculated by gears, after one rotation of a wheel a tooth of a gear connects to the next gear and the same fashion is followed addition is performed

• 1694: Gottfried completed a model of multiplying calculator , which can perform multiplication and division

• 1801: Jacquard invented punch card


• 1830: Charles Babbage conceived a first programmable computer ”Analytical engine”, which could perform calculations printing etc. He designed a system with input section which cloud read holes and spaces punched on cards , mill unit to perform calculation and store unit to hold the numbers.

• 1890: Dr. Herman developed the first electromechanical punched card tabulator, driven by electricity and could sort and select data

• 1930: First analog computer invented by Bush • 1944: First digital computer developed by Aiken, it was

an electromechanical machine contained relays instead of gears


• 1946: ENIAC (Electronics Numerical Integrator and Calculator) invented, it was fully electronic computer. This was designed for military. It was programmed by means of electronic switches and connections and used almost 20,000 Vacuum tubes and created too much heat.

• 1948: Transistor introduced• 1949: EDSAC (Electronics delay storage automatic

calculator) first stored program commuter completed.• 1950: EDVAC (Electronic discreet variable automatic

computer) developed , it was capable of storing instructions eliminating the need of human interventions and reducing the operation time.


• 1951:UNIVAC, first commercial computer developed

• 1964:Integrated circuits introduced • 1965:First minicomputer • 1970’s: Large scale integrated circuits

developed• 1975:First microcomputer • 1980:CPU on a single chip • 1980’s: Super chip developed

Generations of computers

• First generation (1942-1959), Vacuum tubes and magnetic cores

• Magnetic drum as primary storage

• Magnetic tape as secondary storage instead of punched card

• Programmed in machine language (0,1)

• Heat and size issue


• Second Generation (1959-1965)Solid state components (transistor and diodes)

• Smaller size• Faster processing speed • Increased memory with faster access time • Magnetic tape for secondary storage • Programmed I machine and assembly

language


• Third generation (1965-1970) Integrated circuits,

• Increased input and output processing and storage

• Computer memory become volatile

• Time sharing and multiprogramming

• Minicomputer came into use


• Fourth generation (1970-1980) LSI, VLSI, ULSI

• Semiconductor, large memory

• Multiprocessing introduced

• Significant application softwares

• Common use of mini and micro computers

• Advancement in input and output devices


• Fifth Generation (1980-onward)• These machines were equipped with large

primary storage capability and extremely fast processing speed.

• Softwares become much cheaper • Hardware continued to shrink in size while

internal memory increased • Industrial and personal robots replaced human

beings • Huge computers linked in parallel offering

increased computing power

Types of Computer

• Analog computer • Digital computer • Hybrid computer • Analog computer: This computer works on analog

data/quantity. It accepts analog data process it and produce analog information.

• This type of computer do not have storing ability. It just takes the data , process it uptil accurate level of and produce output e.g velocity , temperature, pressure, voltage all of these are analog quantities. That changes by the passage of time e.g Speedo meter of a car showing different speeds at different instants

• Line voltage fluctuations are measured by voltmeter

Types of Computer

• Digital computer • It works on digital data 0/1, it process that data

and produce digital data by numbers• Examples of digital computers are accounting

machines and calculators. Digital computers are more accurate ,precise then analog computers. Analog computers are faster then digital one, as digital takes the time for processing and storing. Digital computers have the storing capability to save the data

Types of Computer

• Hybrid Computer• This type of computer has the properties of both

the analog and digital computers. It has the speed of analog and accuracy of the digital computer. These computers are used in special areas where calculation and measurement is done by both analog and digital manners, e.g air defense system, level/pressure detector system in oil refineries

Classes of computers

• Computers are classified by their physical size, cost , sped , word size.

• Day by day technology advancement making physical size smaller while cost increasing.

• Speed refers to the processing speed of the computer that how many instructions it can execute in stipulated time.

• Word size refers to the size of internal/primary/auxiliary memory that it can contain e.g, 16 bit computer can store data a word of 16 bit in its memory this is called 16 bit computers

Classes of computers• Computers are classified by their, Physical size Cost Speed Word size• Day by day advancement in technology making physical size

smaller while cost increasing. Speed refers to the processing speed of computer, that how many instructions it can execute in stipulated time.

• Word size refers to the size of inter/primary memory that it can hold. E.g. 16 bit computer can store data word of 16 bit in its memory this is called 16 bit computer.

Mainframe Computer Mini Computer Micro Computer Super Computer

Classes of computers• Mainframe Computers:1. Large in size, also having large memory 2. Powerful , expensive3. Designed for huge businesses, banks, universities etc.4. Mainframe supports multiprogramming , and time sharing.5. Mainframe can be 32 bits, 48 bits, or 64 bits.6. Access time is 15 nano seconds, memory up to 100 Mb.• Mini computers:• Small in size, small memory and less expensive.• Designed for medium and small scale organizations (Industrial process control,

data collection, small business applications)• Time sharing, batch processing and online processing are available in mini

computers.• Mini computers are interactive , a user can enter data using keyboard.• Mini computer behaves like a terminal, data is entered and sent to the mainframe

which acts as a host computer and this distributed processing is done.• Access time is 75 nsec.

Classes of computers

• Micro computer:• Smallest in size, Very small memory, least expensive • Designed for personal use that’s why termed as PCs. Designed for small scale

domestic and business use.• They are named as desktop, laptop.• Micro computer use ICs.• Access time is 100 nsec.

• Super Computer:

• These computers require a lot of research to design , and they are very expensive to manufacture.

• The major use of super computer is in solving scientific problems and calculating numbers.

• Can calculate at the rate 400 million numbers per second and are accurate up to 16 decimals.

• They are used as a main tool in simulating the nuclear weapons.

System units and its components

Following are the main basic components of the computer:

Input UnitOutput UnitCentral Processing Unit( CPU / Processor)Memory UnitStorage Unit



• 1. Input Unit: Input unit consists of input devices. Input devices are used to enter data and instructions into computer memory. Examples of input devices are Keyboard, mouse, joystick and microphone etc.


• 2. Output Unit: Output unit consists of output devices. Output devices are used to show results produced by computer after data processing. Examples of output devices are Monitor, Printer, plotter and speaker etc.


• 3. Central Processing Unit:

Central processing unit is also called CPU or Processor. It is the brain of the computer. It performs data processing. It controls overall operations and components of the computer.


• 4. Memory Unit: Memory unit consists of memory devices to store data . RAM is most common example of memory.


• 5. Storage Unit: Storage unit consists of storage media. Storage media are used to store large amounts of data permanently. Examples of storage media are Hard disk, CD, DVD etc.

What is hardware and software

• Hardware, is any part of your computer that has a physical structure, such as the computer monitor or keyboard.

• Software is any set of instructions that guides the hardware and tells it how to do each task. Some examples of software are web browsers, games, and Microsoft Word, Excel etc, peach tree etc.

Microprocessor• A microprocessor incorporates the functions of a central

processing unit (CPU) on a single integrated circuit, It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and provides results as output.

• Microprocessors operate on numbers and symbols represented in the binary numeral system.

• General-purpose microprocessors in personal computers are used for computation, text editing, multimedia display, and communication over the Internet.

• The microprocessors can be classified based on the following features.Instruction Set: It is the set of the instructions that the Microprocessor can execute.Bandwidth: The number of bits processed by the processor in a single instruction.Clock Speed: Clock speed is measured in the MHz and it determines that how many instructions a processor can processed.

Microprocessor

Motherboard

• The motherboard contains the connectors for attaching additional boards, it is the main circuit board of a computer system.

• Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces,

serial and parallel ports, expansion slots, and all the controllers required to control standard peripheral devices, such as the display screen, keyboard, and disk drive.

• Collectively, all these chips that reside on the motherboard are known as the motherboard's chipset.

Motherboard

• Accelerated Graphics Port (AGP)• Peripheral Component Interconnect (PCI)• serial Advanced Technology Attachment

(SATA)

• Integrated development environment (IDE)

Chip

• A small piece of semiconducting material (usually silicon) on which an integrated circuit is embedded. A typical chip is less than square inches and can contain millions of electronic components (transistors, diodes). Computers consist of many chips placed on motherboard

called printed circuit boards.• Chips are available in different packages , SIP, DIP, PGA, SIMM, DIMM.

CPU and its components

• CPU is the administrator of the computer, which not only executes the instructions but also controls al the storage mediums (primary or secondary), I/O activities as well as the different functions of other attached devices. CPU comprises of

Arithmetic Logic Unit (ALU) Control Unit (CU) Main Memory

• Arithmetic logic unit:

• ALU performs all the arithmetic and logic operations. Arithmetic operations are basic operations such as addition, subtraction, multiplication, division. On the other hand logical operations are performed on the basis of comparison of two values. On the result of comparison further actions are taken upon data whether =, < or >.

CPU and its components• Control Unit (CU):• This unit do not perform any processing rather it controls & coordinates the

operations of every individual unit of the computer system, like traffic police controls the traffic and directs it accordingly.

• CU executes the instructions, controls & directs the i/p, informs ALU for processing, arranges temporary or permanent memory and prepares the o/p devices for results.

• Main/Primary Memory:• This is the warehouse of computer system because it holds the information,

which is entered by i/p unit for processing and holds its results as well.• Internal memory has two segments• Program Storage Memory: It holds active program like operating

system.• Data storage Memory: This holds the data/information to be processed

by ALU, and the results ready for outputting.

Machine cycle• Each time the CPU executes an instruction, it takes a series of

steps. The complete series of steps is called a machine cycle. A machine cycle can be divided into two smaller cycles. These are instruction cycle and execution cycle.

• Instruction cycle: In instruction cycle CPU takes two steps--1. Fetching: Before the CPU can execute an instruction, the control unit must retrieve or fetch data from the computer's memory.2. Decoding: Before a command is executed, the control unit must decode the command into instruction set.

• Execution cycle: In execution cycle CPU also takes two steps--1. Executing: When the command is executed, the CPU carried out the instructions in order by converting them into machine code.2. Storing: The CPU may be required to store the result of an instruction in memory.

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Lecture 1