Introduction to Digital Computer

By:-Gourav Kottawar

Contents1.1 Concept of Digital Computer1.2 Types of Software – System software /1.3 Application software / Utility Software.1.4 Compilers, Interpreters, Assemblers, Linker,1.5 Loader

by:-Gourav Kottawar

Introduction• Computer System

A system of interconnected computers that share a central storage system and various peripheral devices such as a printers, scanners, or routers. Each computer connected to the system can operate independently, but has the ability to communicate with other external devices and computers

by:-Gourav Kottawar

by:-Gourav Kottawar

Computer organization1. Computer Organization• The dynamic interaction between the computers• How hardware components operate• How the hardware components are connected together to

from computer system.2. Computer Design• What hardware should be used.• How should they be connected.3. Computer architecture(CA) • Various functional modules such as processors and

memories.• Structuring all these modules together to from a computer

system.• Interface between the machine and the software.

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Computer Architecture

• Two types1.Von – neumann architecture2.Harvard architecture

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Von- neumann Architecture

Von NeumannVon NeumannArchitectureArchitecture

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Von- neumann Architecture

• All computers more or less based on the same basic design, the Von Neumann Architecture!

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Von- Neumann Architecture• Model for designing and building

computers, based on the following three characteristics:

1) The computer consists of four main sub-systems:

• Memory• ALU (Arithmetic/Logic Unit)• Control Unit• Input/Output System (I/O)

2) Program is stored in memory during execution.3) Program instructions are executed sequentially.

by:-Gourav Kottawar

by:-Gourav Kottawar

The Harvard Architecture • Harvard architecture is a computer architecture with

physically separate storage and signal pathways for instructions and data.

• The term originated from the Harvard Mark I relay-based computer, which stored instructions on punched tape (24 bits wide) and data in electro-mechanical counters (23 digits wide).

• These early machines had limited data storage, entirely contained within the data processing unit, and provided no access to the instruction storage as data, making loading and modifying programs an entirely offline process.

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The Harvard Architecture • In a computer with a von Neumann architecture (and

no cache), the CPU can be either reading an instruction or reading/writing data from/to the memory. – Both cannot occur at the same time since the

instructions and data use the same bus system. • In a computer using the Harvard architecture, the CPU

can read both an instruction and perform a data memory access at the same time, even without a cache.

• A Harvard architecture computer can thus be faster for a given circuit complexity because instruction fetches and data access do not contend for a single memory pathway.

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The Harvard Architecture • In a Harvard architecture, there is no need to make

the two memories share characteristics. In particular, the word width, timing, implementation technology, and memory address structure can differ.

• In some systems, instructions can be stored in read-only memory while data memory generally requires read-write memory.

• Instruction memory is often wider than data memory

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The Harvard Architecture

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Generation Of Computers• 1. First Generation (1946-1959)• vacuum tubes as the basic components for memory and

circuitry for CPU (Central Processing Unit). The main features of First Generation are:• Vacuum tube technology• Unreliable• Supported Machine language only• Very costly• Generate lot of heat• Slow Input/Output device• Huge size, Need of A.C.• Non-portable• Consumed lot of electricity

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• Some computers of this generation were:• ENIAC• EDVAC• UNIVAC• IBM-701• IBM-650

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2. Second Generation(1959-1965)• The main features of Second Generation are:• Use of transistors• Reliable as compared to First generation computers• Smaller size as compared to First generation computers• Generate less heat as compared to First generation

computers• Consumed less electricity as compared to First

generation computers• Faster than first generation computers• Still very costly• A.C. needed• Support machine and assembly languages

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2. Second Generation(1959-1965)

• Some computers of this generation were:• IBM 1620• IBM 7094• CDC 1604• CDC 3600• UNIVAC 1108 by:-Gourav Kottawar

3. Third Generation(1965-1971)• The main features of Third Generation are:• IC used• More reliable• Smaller size• Generate less heat• Faster• Lesser maintenance• Still costly• A.C. needed• Consumed lesser electricity• Support high-level language

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Some computers of this generation were:• IBM-360 series• Honeywell-6000 series• PDP(Personal Data Processor)• IBM-370/168• TDC-316

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4. Fourth Generation(1971-1980)• The main features of Fourth Generation are:• VLSI technology used• Very cheap• Portable and reliable• Use of PC's• Very small size• Pipeline processing• No A.C. needed• Concept of internet was introduced• Great developments in the fields of networks• Computers became easily available

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5. Fifth Generation(1980-till date.)• The main features of Fifth Generation are:• ULSI technology• Development of true artificial intelligence• Development of Natural language processing• Advancement in Parallel Processing• Advancement in Superconductor technology• More user friendly interfaces with multimedia features• Availability of very powerful and compact computers at

cheaper rates

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5. Fifth Generation(1980-till date.)

• Some computers types of this generation are:

• Desktop• Laptop• NoteBook• UltraBook• ChromeBook

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4. Fourth Generation(1971-1980)

• Some computers of this generation were:• DEC 10• STAR 1000• PDP 11• CRAY-1 (Super Computer)• CRAY-X-MP (Super Computer)

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Digital Computer• digital computer, any of a class of devices capable of

solving problems by processing information in discrete form. • It operates on data, including magnitudes, letters, and

symbols, that are expressed in binary form—i.e., using only the two digits 0 and 1.

• A digital computer can perform such tasks as to control industrial processes and regulate the operations of machines;

• analyze and organize vast amounts of business data; and simulate the behaviour of dynamic systems

• Example - global weather patterns and chemical reactions in scientific research.

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Characteristics of computer1. Automatic:• These machines are automatic. • Once properly started, they can perform task without

any human intervention. • This makes these devices immensely helpful in

carrying out tedious tasks which may tire normal human brain.

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Characteristics of computer 2 Speed:• Digital computers are discrete systems and operate

in discontinuous steps.• However the speed of operation is very high. They

can carry out trillions of operations in a second.

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Characteristics of computer• 3. Accuracy:• A Digital computer stores the information in encoded

form which guarantees its longevity and accurate retrieval.

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Characteristics of computer 4) Flexibility:• These computers are versatile in a sense that they can

carry out different type of jobs at a time without any interference.

• They modify their behaviour based on the information they process.

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Characteristics of computer5. Memory:• It can store and recall any amount of information

because of its secondary storage facility. The information can be stored and retrieved as long as a user desires. This seldom happens in case of a hum brain.

• To sum it all a digital computer can work speedily, accurately and with all diligence without getting tired.

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Types of computer

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Analog computerAnalog computer measures and answer the

questions by the method of “HOW MUCH”. The input data is not a number infect a physical quantity like tem, pressure, speed, velocity.

• Signals are continuous of (0 to 10 V)• Accuracy 1% Approximately• High speed• Output is continuous• Time is wasted in transmission time

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Analog computer

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Digital Computers

Digital computer counts and answer the questions by the method of “HOW Many”. The input data is represented by a number. These are used for the logical and arithmetic operations.

• Signals are two level of (0 V or 5 V)• Accuracy unlimited• low speed sequential as well as parallel

processing• Output is continuous but obtain when

computation is completed.

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Micro Computer

Micro computer are the smallest computer system. There size range from calculator to desktop size. Its CPU is microprocessor. It also known as Grand child Computer.

• Application : - personal computer, Multi user system, offices.

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Mini Computer

These are also small general purpose system. They are generally more powerful and most useful as compared to micro computer. Mini computer are also known as mid range computer or Child computer.

• Application :- Departmental systems, Network Servers, work group system.

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Mini computer

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Main Frame Computer

Mainframe computers are those computers that offer faster processing and grater storage area. The word “main frame” comes from the metal frames. It is also known as Father computer.

• Application – Host computer, Central data base server.

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Super Computer

• Super computer are those computer which are designed for scientific job like whether forecasting and artificial intelligence etc. They are fastest and expensive. A super computer contains a number of CPU which operate in parallel to make it faster. It also known as grand father computer.

• Application – whether forecasting, weapons research and development.

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Super computer

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Classification of Digital computer • Desktop• Workstation• Notebook• Tablet PC• Handheld computer• Smart Phone

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workstation

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Tablet PC

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Handheld PC(PDA)

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Smart phone

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Components Of Computer System

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Block Diagram Of Computer System

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• 1. Input: • This is the process of entering data and programs in to the computer

system. • You should know that computer is an electronic machine like any other

machine which takes as inputs raw data and performs some processing giving out processed data.

• Therefore, the input unit takes data from us to the computer in an organized manner for processing.

by:-Gourav Kottawar

by:-Gourav Kottawar

2. Storage: • The process of saving data and instructions permanently is known as

storage. • Data has to be fed into the system before the actual processing starts. • It is because the processing speed of Central Processing Unit (CPU) is

so fast that the data has to be provided to CPU with the same speed. • Therefore the data is first stored in the storage unit for faster access

and processing. This storage unit or the primary storage of the computer system is designed to do the above functionality. It provides space for storing data and instructions.

• The storage unit performs the following major functions: • All data and instructions are stored here before and after processing. • Intermediate results of processing are also stored here.

by:-Gourav Kottawar

by:-Gourav Kottawar

3. Processing: • The task of performing operations like arithmetic and

logical operations is called processing. • The Central Processing Unit (CPU) takes data and

instructions from the storage unit and makes all sorts of calculations based on the instructions given and the type of data provided.

• It is then sent back to the storage unit.

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• 4. Output: • This is the process of producing results from the data for

getting useful information. • Similarly the output produced by the computer after

processing must also be kept somewhere inside the computer before being given to you in human readable form.

• Again the output is also stored inside the computer for further processing.

by:-Gourav Kottawar

by:-Gourav Kottawar

• 5. Control: The manner how instructions are executed and the above operations are performed. Controlling of all operations like input, processing and output are performed by control unit. It takes care of step by step processing of all operations inside the computer.

• FUNCTIONAL UNITS • In order to carry out the operations mentioned in the

previous section the computer allocates the task between its various functional units. The computer system is divided into three separate units for its operation. They are

• 1) arithmetic logical unit • 2) control unit. • 3) central processing unit.

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• Arithmetic Logical Unit (ALU)  Logical Unit

• Logical Unit :After you enter data through the input device it is stored in the primary storage unit. The actual processing of the data and instruction are performed by Arithmetic Logical Unit. The major operations performed by the ALU are addition, subtraction, multiplication, division, logic and comparison. Data is transferred to ALU from storage unit when required. After processing the output is returned back to storage unit for further processing or getting stored.

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• Control Unit (CU) • acts like the supervisor seeing that things are done in proper

fashion. • Control Unit is responsible  for  co ordinating various operations

using time signal. • The control unit determines the sequence in which computer

programs and instructions are executed. • Things like processing of programs stored in the main memory,

interpretation of the instructions and issuing of signals for other units of the computer to execute them.

• It also acts as a switch board operator when several users access the computer simultaneously.

• Thereby it coordinates the activities of computer’s peripheral equipment as they perform the input and output.

by:-Gourav Kottawar

by:-Gourav Kottawar

• Central Processing Unit (CPU)

• The ALU and the CU of a computer system are jointly known as the central processing unit.

• the brain of any computer system. • It is just like brain that takes all major decisions, makes

all sorts of calculations and directs different parts of the computer functions by activating and controlling the operations.

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Components Of Computer System

• A computer system consists of both hardware and information stored on hardware.

• Information stored on computer hardware is often called software.

• The hardware components of a computer system are the electronic and mechanical parts.

• The software components of a computer system are the data and the computer programs.

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Components Of Computer System• The major hardware components of a computer system are: • Processor• Main memory• Secondary memory• Input devices• Output devices

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Components Of Computer System• For typical desktop computers, the processor, main

memory, secondary memory, power supply, and supporting hardware are housed in a metal case.

• Many of the components are connected to the main circuit board of the computer, called the motherboard.

• The power supply supplies power for most of the components.

• Various input devices (such as the keyboard) and output devices (such as the monitor) are attached through connectors at the rear of the case.

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Components Of Computer System

by:-Gourav Kottawar

Components Of Computer System

by:-Gourav Kottawar

Components Of Computer System

by:-Gourav Kottawar

Hardware Vs Software

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Hardware Vs Software

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Hardware Software

DefinitionDevices that are required to store and execute (or run) the software.

Collection of instructions that enables a user to interact with the computer. Software is a program that enables a computer to perform a specific task, as opposed to the physical components of the system (hardware).

Types Input,storage,processing,control, and output devices.

System software, Programming software, and Application software.

Examples

CD-ROM, monitor, printer, video card, scanners , label makers, routers , and modems.

Quickbooks, Adobe Acrobat, Winoms-Cs, Internet Explorer , Microsoft Word , Microsoft Excel

Inter dependency

Hardware starts functioning once software is loaded.

To deliver its set of instructions, Software is installed on hardware.

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Hardware Software

Failure

Hardware failure is random. Hardware does have increasing failure at the last stage.

Software failure is systematic. Software does not have an increasing failure rate.

Durability Hardware wears out over time.

Software does not wear out over time. However, bugs are discovered in software as time passes.

Nature Hardware is physical in nature. Software is logical in nature.

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Types Of Software• Evolution of System Software:• Two components of program development

and execution cost are:• Cost of the computer system• The Manpower cost• To measure the optimal effectiveness above

two factors should be weighed against each other

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• First step in the evolution of system software was the development of a language translator

• In the early days , program had to be written in the machine language

• Translators for the low level programming language were termed as assemblers

• And such low level languages were called Assembly language

• Though the assembly language permitted easy writing but still it was highly machine dependent.

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• The complexities associated with the use of assembly language led to the evolution of machine independent programming languages

• These languages were termed high level languages• Called as HLL because they required only a

programmer to specify logic for writing a program

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• System Software: • It is a program required to co-ordinate all activities of

computer system.• System software is a collection of programs which are

executed as needed to perform following functions:• Receiving and interpreting user commands• Entering ,editing and storing the Application program in

secondary storage• Managing the storage and retrieve files from disk• Running the applications as desired by the user• Controlling I/O units for inputting data and displaying result• Linking and loading the desired Library routines

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• A system program is one which is required for the effective execution of a general user program

• Execution includes all activities concerned with the initial input of the program and various stages of its processing by computer system

• Such as editing storage, translation, relocation, linking,and eventual execution

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Application Software• Application programs are • Written in high level language• Used by programmer for writing computer instructions• Used to solve a specific problem or does a specific task• Application software allows user to do things like creating

text documents,playinggames,Listeningto music or surfing the web

• Provides user-oriented or output-oriented functionality • E.gTally,TurboC

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Utility Software• It is a kind of system software designed to

help ,analyze ,configure optimize and maintain computer• A single piece of utility software is usually called a utility or tool• It is used with application software• It usually focuses on how the computer infrastructure operates• Most of the operating systems come with several preinstalled

utilities• E.gDisk storage Utilities, Disk defragmenter, Disk Checker,

Disk Cleaners, Disk Space analyzers, Backup Utilities, Disk Compression

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Utility Software• It is a kind of system software designed to

help ,analyze ,configure optimize and maintain computer• A single piece of utility software is usually called a utility or tool• It is used with application software• It usually focuses on how the computer infrastructure operates• Most of the operating systems come with several preinstalled

utilities• E.g Disk storage Utilities, Disk defragmenter, Disk Checker,

Disk Cleaners, Disk Space analyzers, Backup Utilities, Disk Compression

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Compilers• Convert user programs written in high level language into a

machine understandable format by reading complete program as input and produces assembled program as output

Interpreters• Convert user program written in high level language into system

program by reading line by line complete program as input and produces assembled program as output.

• Converts a high level code into m/c instructions line by lineAssembler• Converts assembly language program in to machine language

equivalent

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Linker• A special program whose main purpose is to join together a

number of relocatablemodules which have been loaded into memory .

• Relocatablemodule is the one which needs to be relocated before it can be used.

• E.gLinking Library files

Loader• A special program whose purpose is to load other programs or

modules into memory• E.gDrivers

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STEPS INVOLVED IN COMPILATION

Preprocessing:• During the preprocessing stage, comments, macros,

and directives are processed.Lexical Analysis:• Also called scanning • It involves examining source program from left to

right ,character by character and grouping them into tokens having collective meaning

• Breaking down the source files into keywords, constants, identifiers, operators ,Tokens

• The output of this phase goes to the next phaseby:-Gourav Kottawar

TASKS PERFORMED DURING LEXICAL ANALYSIS

• All comments ,tabs, blanksspaces and machine characters are removed

• Error messages occur in a source program are produced

Syntactical Analysis:• The process of combining the tokens into• well-formed expressions, statements, and programs.• Checks whether the expression is syntactically

correct or not• Report syntax errors if any

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Semantic Analysis:• Process of examining the data types and values of the statements used to

make sure they make sense.• An important component of semantic analysis is type checking• Here the compiler checks that each operator has operands that are

permitted by the source language specificationCode Optimization:• The compiler analyzes the code to see if improvements can be made • for e.gby making use of pointers when accessing arraysCode Generator:• After the code is optimized code generator generates the machine code or

object code and finally linker links all the object modules to generate the executable code

by:-Gourav Kottawar

by:-Gourav Kottawar