• Unit 1. Basic Concepts• What is a computer- meaning, stages of evolution,

generations• Characteristics of a Computer, Advantages and

Limitations. • Basic computer operations and functional units.• Types of Computers- based on data handling

technology, purpose and size• Applications of computers. • Data Representation. Binary number system,

conversion from binary to decimal and vice versa, Computer Codes- BCD, EBCD, ASCII, ISCII, Unicode.

What Is a Computer?

Electronic device operating under the control of instructions stored in its own memory

•Accepts data– Raw facts, figures, and symbols

•Processes data into information – Data that is organized, meaningful, and useful

•Produces and stores results

History of the Computers• Earliest device: Abacus 600BC

• 1642: first mechanical adding machine by Blaise Pascal

• 1671: first calculator for multiplication by Baron Gottfried Wilhelm von Leibniz of Germany

• 1822: Difference machine by Charles Babbage to produce mathematical and Statistical tables

• 1880: keyboard machines in US, punched cards by Herman Hollerith

• 19th century: attempts to build mechanical computers

• Early 20th century: mechanical counting systems (cash registers, etc.)

• Stages of evolution-– 1937-44: Mark I Computer-ASCC (Automatic Sequence Controlled

Computer)– 1939-42-ABC (Atanasoff-Berry Computer)– 1943-46: ENIAC (Electronic Numerical Integrator And Calculator)– 1946-52: EDVAC (Electronic Discrete Variable Automatic Computer)– 1947-49: EDSAC (Electronic Delay Storage Automatic Calculator)– 1948: Manchester Mark I– 1951:UNIVAC I (Universal Automatic Computer)

• Generations- Key hardware technologies, Key Software technologies, Key Characteristics, Some representative systems – FIRST GENERATION (1941-1955)– SECOND GENERATION (1956-1964)– THIRD GENERATION (1964-1974)– FOURTH GENERATION (1975-1989)– FIFTH GENERATION (1989-PRESENT)

Computer Generations

FIRST GENERATION (1941-1955)Key hardware technologies• Vacuum tubes; electromagnetic relay memory;

secondary storage: punched cards & punched tapesKey Software technologies• Machine and assembly languages; • stored program concept; mostly scientific applicationsKey Characteristics• Bulky in size; Lot of air-conditioning required; very slow;

consumed lot of power; highly unreliable; limited commercial use; commercial production difficult and costly; difficult to use

Some representative systems • ENIAC, EDVAC, EDSAC, UNIVAC I, IBM 701

SECOND GENERATION (1956-1964)

Key hardware technologies• Transistors; smaller circuits, magnetic cores memory; magnetic

tapes and disks secondary storage in addition to punched cards

Key Software technologies• Batch operating system; high-level programming languages; scientific

and commercial applications

Key Characteristics• Faster, smaller, more reliable and easier to program than previous

generation systems; generated less heat, required less power; commercial production was still difficult and costly

Some representative systems • Honeywell 400, IBM 7030, CDC 1604, UNIVAC LARC

THIRD GENERATION (1964-1974)Key hardware technologies• Integrated Circuits with SSI and MSI technologies; • larger magnetic cores memory; larger capacity disks and magnetic

tapes secondary storage; minicomputers

Key Software technologies• Timesharing operating system; standardization of high-level

programming languages; unbundling of software from hardware

Key Characteristics• Faster, smaller, more reliable, easier and cheaper to produce

commercially, easier to use, and easier to upgrade than previous generation systems; scientific, commercial and interactive on-line applications

Some representative systems • IBM 360/370, PDP-8, PDP-11, CDC 6600

FOURTH GENERATION (1975-1989)

Key hardware technologies• Microprocessors; ICs with VLSI technology;

semiconductor memory; larger capacity hard disks as inbuilt secondary storage; magnetic tapes and floppy disks as portable storage media; spread of high-speed computer networks

Key Software technologies• GUI; multiple windows on a single terminal screen;

Operating systems for PCs; multiprocessing operating systems; UNIX operating system;

• C programming language; Object oriented design and programming; PC-based applications; network-based applications; supercomputing applications

FOURTH GENERATION (1975-1989)

Key Characteristics• Small, affordable, reliable, and easy to use PCs; • more powerful and reliable mainframe systems and

supercomputers; totally general purpose machines;• easier to produce commercially; easier to upgrade; rapid

software development possible

Some representative systems • IBM PC and its clones, Apple II, TRS 80, V AX 9000,

CRAY-l, CRAY-2, CRAY–X/MP

FIFTH GENERATION (1989-PRESENT)

Key hardware technologies• ICs with ULSI technology; larger capacity main memory;

larger capacity hard disks with RAID support; portable storage: optical disks, pen drives

Key Software technologies• Microkernel-based operating systems; multithreading

operating systems; parallel processing • distributed computing systems; World Wide Web; internet-

based applications; • multimedia applications; more complex supercomputing

applications; artificial intelligence

FIFTH GENERATION (1989-PRESENT)

• Key Characteristics• more powerful, cheaper, reliable, and easier to use desktop

machines; Portable computers; notebook computers; workstations; powerful servers; very powerful supercomputers; totally general purpose machines;

• easier to produce commercially; easier to upgrade; rapid software development possible

• Some representative systems • IBM notebooks, Pentium PCs, SUN Workstations, IBM

SP12, SGI Origin 2000, PARAM 10000, Xybernaut Corp’s personal wearable computer: POMA

Technology

• 1965: Moore’s law [Gordon Moore]

– Computational power doubles every 18 months• Speed of Microprocessors and Size of Main Memory &

Hard Disk Double Every 18 Months

• Drives functionality, performance, cost

• Corollary to Moore’s Law:

– Cost halves every two years

CHARACTERISTICS OF A COMPUTER

1. Automatic. • Computers are automatic machines because once started

on a job, they carry on until the job is finished, normally without any human assistance.

• However, computers being machines cannot start themselves. They have to be instructed. The set of instructions is called a computer program.

2. Speed. • Speed refers to the amount of time a computer takes in

accomplishing a task or completing an operation. • Computers are capable of performing 100 million

calculations per second. (MIPS- Million Instructions Per Second).

3. Accuracy. • Accuracy refers to the degree of exactness with which • computations are made and operations are performed. The

accuracy of a computer is consistently high. If the input data entering the computer are correct and if the program of instructions is reliable, then computer generally will produce accurate output.

• Errors may occur due to bad programming, erroneous data and deviations from procedures which are in fact the errors caused by human beings. Errors attributable to hardware are normally detected and corrected by the computer system itself.

4. Diligence. • Unlike human beings, a computer is free from monotony,

tiredness, lack of concentration, etc., and hence can work for hours together without creating any error and without grumbling.

5. Versatility.

• Versatility refers to the ability of computers to perform a variety of tasks simple as well as complex.

• Computers are versatile unless designed for a specific application.

• A general purpose computer is capable of being used in any area of application, viz., business, scientific, statistical, technological, communications, etc.

6. Reliability• Reliability refers to the ability with which the computers

remain functional to serve the user. • Computer systems are well-adapted to perform repetitive

operations. They are immune to tiredness, boredom or fatigue.

6. Storage• It refers to the amount of data a computer system can store

and access. • A computer can store and recall any amount of information

because of its secondary storage capability. • Every piece of information can be retained as long as

desired by the user and can be recalled as and when required.

ADVANTAGES OF A COMPUTER

• The advantages of the computers can be judged from the various characteristics like, High Speed, Accuracy, Diligence, Versatility, Power of remembering, storage, mentioned in its characteristics.

LIMITATION OF A COMPUTER1. Lack of Common Sense: Computer systems as on date do not possess any

common sense because no fool proof algorithm has been designed to program Common sense. Computers work according to a stored program(s).

2. Zero IQ. Computers are dumb devices with zero

Intelligence Quotient. They possess no intelligence of their own. They cannot visualize and think what exactly to do under a particular situation, unless they have been programmed to tackle that situation.

3. Lack of Decision making

Computers cannot take decisions on their own unless programmed for it.

If a computer has not been programmed for a particular decision situation, it will not take decision due to lack of wisdom and evaluating faculties.

4. No Feelings

Computers are devoid of emotions. They have no feelings and no instincts because they are machines.

Application of Computers

• Education, Finance, Government, Healthcare, Science, Publishing, Travel, Manufacturing

• Computers cost-effective for– National security – weapons design

– Enterprise computing – banking

– Departmental computing – CAD, CAM

– Personal computer – spreadsheets, email, web

• Countless industries revolutionized: aviation, astronomy, engineering, long range weather forecasting, airlines & railway reservation, entertainment

• Basic computer operations– Input – Storage– Processing– Output

• Functional units– Processor/Central Processing Unit

• ALU, CU and Internal processor memory

– Input Unit– Output Unit– Storage Unit

Storage

ProcessorInput Output

Von Neumann’s Definition

A Computer has…

1. Processor/Central Processing Unit

The electronic component that interprets and carries out the basic instructions that operate the computer

2. Input Unit

Accepts instructions and data

3. Output Unit

communicates result to the user

4. Storage Unit

Stores temporary and final results

Central Processing Unit (CPU )• interprets, coordinates the operations and

supervises the instructions.• Controls usage of main memory to store data and

instructions• Highly complex, extensive set of electronic circuitry

which executes stored program instructions• necessary circuits to create CPU are fabricated on

a microprocessor• Main subsystems: ALU, CU and Internal processor

memory (Cache & Registers)

Subsystems of CPU1. Control unit

• Directs computer system to carry out, or execute, stored program instructions

• Directs flow between memory and ALU• Directs flow between CPU and I/O devices• Repeats 4 basic operations

– Fetch instruction– Decode instruction– Execute instruction– Store results

2. Arithmetic and logic unit • Performs arithmetical and logical operations• AU: performs actual computing and carries out

arithmetic calculations, such as +, -, X and ÷.• LU: makes logical operations such as comparison

(=, !=, <,>,≤, ≥) of numbers, letters, or special characters and take action based on the result of comparison

3. Internal Processor memory

1. Cache Memory

High speed, expensive piece of memory, which is used to speed up memory retrieval process

• CPU comes with a small amount of cache compared main memory due to its higher cost

• Computer uses logic to determine most frequently accessed data and keeps them in cache.

• Made from high speed static RAM that reduces the access time of the data

Cache Memory• Categorised into three levels: L1 Cache , L2 Cache and L3 Cache • L1 Cache:

– Primary Cache, closest to the processor– Size: 8 to 64 KB or more– Very fast, runs at the speed of the processor since it is integrated into it

• L2 Cache:– Larger but slower– Recent accesses not picked by L1 Cache– Size: 64 KB to 2 MB– Also found on CPU

• L3 Cache:– Extra cache built into motherboard between the processor and main memory– Speeds up processing operations, reducing time gap b/w request and retrieving

of data and instructions much more quickly than main memory– Size: 3 MB or more

Subsystems of CPU2. RegistersSpecial purpose, high speed temporary memory units for holding data, instructions, addresses, and intermediate results of calculations–Working memory of CPU, hold the information that CPU is currently working on

Register Name Function

Program Counter Keeps track of next instruction to be executed

Instruction Register Holds the instruction to be decoded by CU

Memory address Register Holds address of next location in memory to be accessed

Memory Buffer Register Store data either coming to CPU or data being transferred by CPU

Data Register Storing operands and other data

Computer Memory

• Primary memory Vs. Secondary memory

• Primary– RAM & its types- (static Vs. dynamic)– ROM & its types- (PROM, EPROM, EEPROM,

UVPROM, Flash memory)– Cache memory, Registers

Memory• Electronic holding place for instructions & data where

the computer’s processor can reach quickly.• Holds intermediate results during course of calculations

and provides data as and when required1. Internal processor memory

2. Primary memory

3. Secondary memory

1. Internal Processor memory: fastest, most expensive, compensate speed gap between primary memory and processor

1. Cache

2. Special registers

Primary Memory• Processes or directly stores and retrieves data from the

secondary memory• Internal storage called primary memory or main

memory• CPU can access the main memory in random manner,

i.e., any location to read information from it or store information in it

• Primary Memory is implemented by two types of memory technologies, viz., RAM and ROM

Primary Memory

•Random Access Memory (RAM)– Block of sequential memory locations each of

which has a unique address determining the location & those locations contain a data element

– Temporary holding place for data waiting to be processed, application programs and the operating system

– Addressable and volatile– Read/write memory– 2 categories: DRAM & SRAM

Dynamic RAM• Holds data in dynamic manner with the help of refresh

circuitry• Unstable: keeps refreshing the content of each memory

cell by reading it several hundred times per second to maintain the data

• Used for system’s main memory because its cheap & small

Static RAM• Retains contents as long as power is provided to the

memory chips• Does not need to be refreshed periodically• Fast but more expensive than DRAM• Used as cache memory due to its high speed

Read-Only Memory (ROM)– Holds computer start up instructions and routines in BIOS– Read by CPU each time it is switched on– Non-volatile: contents not lost even if power failure; no current

required for information to remain stored– Firmware: Hard wired instructions, read only, i.e. can’t be changed

by the user– Random access in nature– Used even in calculators & peripheral devices s.a. laser printers– Types: PROM, EPROM, EEPROM

PROM- Programmable ROM• Cheap blank PROMs available• Programmable only once

EPROM-Erasable PROM• Can be erased & reprogrammed• Entire chip can be erased by exposing to UV light, also

called UVEPROM• More expensive than PROM• Used in software development and testing by R&D

personnel

EEPROM-Electrically EPROM• Can be erased by electrical charge, one byte at a time• Flexible, easier to alter than UVEPROM but slow• Used to store programmable instructions in peripheral

devices

Flash ROM• constantly powered non-volatile memory that can be

erased and reprogrammed in blocks• variation of EEPROM used to hold control code s.a. BIOS • Also used in digital cellular phones, MP3 players, modems,

digital camera, etc.

Virtual memory– Hard disk used as an extension of RAM– Data swapped between HD and RAM as needed by the

processor– Imaginary memory supported by OS

3. Secondary Memory• Auxiliary memory, back up storage for software program &

data• Hard disk, magnetic disk, magnetic tapes, floppy disks,

CDROM, DVDROM, Pen drives etc• Less expensive as compared to primary memory• Much larger storage capacity than primary memory• Not directly accessible by processor, primary memory has

a faster access time as compared to secondary memory• Data, instructions stored are permanent in nature; can be

removed only if user wants it.

Categories of Computers

1. According to Technology•Analog Computers•Digital computers•Hybrid Computers2. According to Purpose•Special Purpose Computer

– Scientific Computers– Business Computers

•General purpose computer

Categories of Computers

3. According to Size • Super Computer• Main Frame Computer• Mini Computer• Micro Computer• Personal Computers (PCs)• Work Stations• Portable computers- Notebook, Netbook• Handheld- Personal Digital Assistants

4. According to Role• Server• Client• Network

According to Technology.Analog Computers•Principle of measurement•Measure continuous physical magnitudes, such as pressure, voltage, temperature etc.•Used for scientific & engineering purpose•Give approximate results because quantities vary continuously•Accuracy is less though very fast

Digital computers•Operates with information, numerical or otherwise represented in a digital form•Accepts data (text, sound, graphic & video) through various input devices, converts data into electronic pulses, performs arithmetic and logical operations, processing and give results.•More accurate and faster than analog computers

According to Technology.

Hybrid Computers•These computers incorporate the technology of both, Analog and Digital computers•Measuring feature of an analog computer and computational feature of a digital computer•Used for scientific, engineering, industrial applications

According to PurposeGeneral purpose computer•Perform a variety of tasks

•Store a number of programs for various applications ranging from business, scientific, educational, social and other applications

•Though versatile, they lack speed & efficiency

Special Purpose Computer• dedicated computer, designed to handle specific problem or to perform special tasks, e.g. airlines reservation, satellite tracking, Air Traffic Control, medical diagnosis, space applications, weather forecasting, banking operations

•Very quick & efficient

Scientific ComputersDesigned to best suited for large mathematical calculations.

Business ComputersThese will lack or take more time in scientific calculation, but be fully equipped to produce well layout business reports.

Super Computer• fastest computing devices ever invented • Speed measured in teraflops (1012 FLoating-point Operations

Per Sec).• Use Multi processing and parallel processing• consist of thousands of integrated microprocessors, main

memory of around 16 GB and secondary memory 1000 GB• e.g., PARAM 10000, PACE, CRAY, Cyber, IBM Blue Gene• IBM’s Blue Gene installed at Lawrence Livermore National

Laboratory (LLNL) in California operates at 360 teraflops, used to study cosmology and the behaviour of stellar binary pairs, laser-plasma interactions, and the behaviour and aging of high explosives.

According to Size

Main Frame Computer• processes several millions of instructions per second • bigger & more expensive than workstations• Used in banks and insurance cos., processing on-line

transactions, ERP, Survey etc.• Large disks to store terabytes of data, • transfer data from disk to main memory at several hundred

MB per sec, • process 100 million transactions per sec.• Proprietary OS• e.g., IBM’s System/390, VAX 8000, CDC 6600

According to Size

Mini Computer• middle sized special purpose computers• used in transaction processing applications• as interface between main frame and WAN,• Serves as a centralised storehouse for a cluster of

workstations or as a network server• Usually multi-user systems, used in industries, research

organisations, colleges & universities• work well with distributed data processing, supports 4 to

200 simultaneous users• VAX 7500, IBM (8000 series), PDP-11.

According to Size

Work Stations• desktop machines having a powerful processor than a micro (10 times

speedier than PC)

• Main memory: several GBs

• HD: 100s of GB

• support multi-user environment

• Operating System: UNIX or its derivatives like AIX (IBM), Solaris (SUN), HP-UX (HP)

• a sophisticated screen display featuring a high resolution colour graphics, large video screens, inbuilt h/w to connect to LAN

• meet computing requirements of engineers, architects

• Business & industry usage for executing numeric, graphic intensive multimedia applications s.a. CAD, simulation of complex systems

• Also called super micros.

• e.g. DEC, IBM, Sun Workstations

According to Size

Micro Computer• Small, low cost digital computer

• most familiar kind of computers

• Originally designed for single user, when networked together can serve more than one user

• Many uses

• these include: desktop, laptop, PDAs

According to Size

Desktop computer• Personal computer, stand-alone use by an

individual

• Not expensive

• Used by individuals and small businesses

• MS-Windows, Windows XP, LINUX

• Apple Macintosh (Power PC Processor), IBM PCs (Intel Pentium processor)

According to Size- Micro computer

Portable computers • Laptop/Note Books

• combine the power of PC with mobility, powered with battery.

• Weight around 2kg

• Keyboard, flat screen LCD

• Wireless connectivity to networks

• Cost more than Desktop

According to Size- Micro computer

Personal Digital Assistants• PDAs are much smaller than laptops, handheld computer• also known as Palmtop, Simputer• combine pen input (i.e. stylus), writing recognition and

communication capabilities• No hard disk, use small cards to store programs and data• Runs on batteries• Limited processing capabilities and memory• E.g., Palm pilots, Mind Spring, i-Paq, Casio Cassiopeia,

Apple Newton, Franklin eBookMan

According to Size- Micro computer

According to RoleServer• Large computer, manages shared resources and provides

services to clients• specific purpose such as high performance numerical

computing (called compute server), web page hosting, database store, printing, etc.

• Interactive large screens not necessary as in case of workstations

• Compute server: high performance processors, large main memory

• Database server: large on-line disk storage (100s of GB)• Print server: support several high speed printers• May be a workstation, mainframe or even a super

computer

According to RoleClient

• A single user PC or workstation that provides a highly user friendly interface to the end user

• Runs client processes which sends service request to server

Network

• Interconnects all the clients and servers of the client-server computing environment

Data Representation•Binary number system & its relevance

•Conversion of numbers among

•Binary

•Octal

•Hexadecimal

•Decimal

•Binary representation of integers and real numbers

•Sign and magnitude representation

•Complement representation

•Performing simple arithmetic on binary numbers

•Computer Codes- BCD, EBCD, ASCII, ISCII, Unicode.

Number Systems: Positional, Non Positional (Roman)

Positional: Decimal (base 10), Binary-2, Octal-8, Hexadecimal-16

BINARY NUMBER SYSTEM• In binary number system, there are only two states: 0 and

1. These are also called binary digits or bits.• The use of binary number system in digital computers has

made the design of digital computers very simple. All information is represented using zeros and ones.

• 0 and 1 in binary number system are used to represent decimal numbers 0 and 1, respectively.

DATA REPRESENTATION

BINARY NUMBER SYSTEMDecimal Number Binary Number

0 0000

1 0001

2 0010

3 0011

4 0100

5 0101

6 0110

7 0111

8 1000

9 1001

10 1010

Converting Binary to Decimal(a) 101112

• the right most bit is called the least significant bit (LSB), its weight is 20, i.e. 1.

• The next bit on the left side of LSB has a weight of 21, i.e. 2.• The next bit has a weight of 22, i.e. 4, and so on. • Thus, the rightmost bit, which is also called the most significant bit

(MSB) in 10111 has a weight of 24, i.e. 16. 101112

• = 1 x 24 + 0 x 23 + 1 x 22 + 1 x 21 + 1 x 20

• =1x16+0x8+1x4+1x2+1x1 • = 16 + 0 + 4 + 2 + 1 = 2310

(b)101010112

• = 1 x 27 + 0 x 26 + 1 x 25 + 0 x 24 + 1 x 23 + 0 x 22 + 1 x 21 + 1 x 20

• = 1 x 128 + 0 x 64 + 1 x 32 + 0 x 16 + 1 x 8 + 0 x 4 + 1 x 2 + 1 x 1 • = 128 + 0 + 32 + 0 + 8 + 0 + 2 + 1 • = 17110

Converting Decimal to Binary• Divide decimal number by 2.

• Then the result (quotient) is successively divided again by 2, till it cannot be divided further.

• The binary number is obtained by writing the remainders of these divisions backward.

Convert 4210 into binary number

2 42 Remainder

21 0

10 1

5 0

2 1

1 0

0 1

(42)2= (101010)10

COMPUTER CODES• Commonly used coding systems: BCD, ASCII, EBCDIC, Unicode,

etc. • 1. Binary-coded decimal (BCD) is a numeral system used in

computing and in electronics systems. In BCD, numbers are represented as a sequence of decimal digits in which each digit is represented by four bits:

Digit bits Digit bits Digit bits Digit bits Digit bits

0 0000 2 0010 4 0100 6 0110 8 1000

1 0001 3 0011 5 0101 7 0111 9 1001

Binary-coded decimal (BCD)• To encode a number such as 127, for example, each of the

decimal digits is encoded using the bit pattern shown above, that is: 0001, 0010, 0111.

• Most computers store data in eight-bit bytes, so there are two common ways of storing four-bit BCD digits in those bytes: – Ignore the extra four bits of each byte, usually filling them with

either zero bits or one bits (as in EBCDIC)– Store two digits per byte, called "packed" BCD.

• Packed BCD numbers also usually end with a sign 'digit', for which the preferred values are 1100 for + and 1101 for -.

• Thus the number 127 would be represented as (11110001, 11110010, 11110111) in EBCDIC or (00010010, 01111100) in packed BCD.

• BCD is wasteful (about 1/6 of the available memory is wasted, even in packed BCD),

2. EBCDIC (Extended Binary Coded Decimal Interchange Code)

• EBCDIC was devised in the 1963-1964 by IBM • It is an 8-bit character encoding used on IBM mainframes and

AS/400s. • It is descended from punched cards and the corresponding six bit

binary-coded decimal code that most of IBM's computer peripherals of the late 1950s and early 1960s used.

• Single byte EBCDIC takes up eight bits, which are divided in two pieces. – The first four bits are called the zone and represent the category of

the character, – the last four bits are the called the digit and identify the specific

character. • It was created to extend the Binary Coded Decimal that existed at the

time.

3. AMERICAN STANDARD CODE FOR INFORMATION INTERCHANGE (ASCII)

• ASCII (generally pronounced ski), is a character set and a character encoding based on the Roman alphabet as used in modern English and other Western European languages.

• Most commonly used by computers and other communication equipment to represent text and by control devices that work with text.

• ASCII specifies a correspondence between digital bit patterns and the symbols/glyphs of a written language, thus allowing digital devices to communicate with each other and to process, store, and communicate character-oriented information.

• ASCII is, strictly, a seven-bit code, meaning that it uses the bit patterns representable with seven binary digits (a range of 0 to 127 decimal) to represent character information.

• Later ASII-8 was developed by IBM which is 8-bit code with 256 characters.

ASCII• ASCII was first published as a standard in 1968 by the American

Standards Association (ASA), which later became ANSI (American National Standards Institute). There are many variations of ASCII.

• The first thirty-two codes (numbers 0-31 decimal) in ASCII are reserved for control characters: codes that were not originally intended to carry information, but rather to control devices (such as printers) that make use of ASCII. – For example, character 10 represents the "line feed" function (which

causes a printer to advance its paper), and character 27 represents the "escape" key found on the top left of common keyboards.

– Code 127 (all seven bits on) is another special character known as "delete".

• Code 32 is the "space" character, denoting the space between words, which is produced by the large space bar of a keyboard.

• Codes 33 to 126 are called the printable characters, which represent letters, digits, punctuation marks, and a few miscellaneous symbols.

Unicode

• Unicode Standard replaced ASCII• Developed by Unicode Consortium in 1991• Provides unique code for every character• Supports international languages• Irrespective of platform, program, language• Adopted by Apple, HP, IBM, Microsoft, Oracle, SAP, Sybase,

etc.

Unit 2.Essential components of Computers

• Meaning of Hardware, Software, Firmware, Live-ware

• Hardware components in brief.

• Relationship between hardware and software

Unit 2.Essential components of Computers

• Hardware, Software, Firmware, Live-ware• Relationship between hardware and software

• System Software

• Overview of operating system

• Application software

Components of Computer System• Hardware: physical components, electronic & electro

mechanical components• Software: set of computer programs; system software &

application software computer program: sequence of instructions written in a language that

can be understood by a computer and instructs the computer to perform a task

• Liveware: human beings that interact with the computers; system analysts, programmers and operators

• Firmware: software embedded in a hardware device that allows reading & executing the software but does not allow modification e.g., BIOS in a ROM

Hardware Components

What is an input device?• Hardware used to enter data and instructions

What is an output device?• Hardware that conveys information to one or more people

What is storage?

Holds data, instructions, and information for future use

Storage media• Physical material on which data, instructions, and

information are stored

Storage device• Records and retrieves items to and from storage media

SoftwareSoftware Categories:

1. System Software1. System Management Program

1. Operating System

2. Device Drivers

3. System Utilities

2. System Development Program1. Programming Languages

2. Language processors

3. Linkers

4. Loader

2. Application Software

System Vs. Application software

System Software• Low level programs that

interact with computer at low level

• Provide basic non-task specific functions

• Control the operations & extend processing capability of computer system

Application Software• End user programs

• User oriented programs that perform specific tasks

• Controlled by system software

Application Software

Application software:

1. Word-Processing Software

2. Spreadsheet Software

3. Database Software

4. Graphics Software

5. Personal Assistance Software

6. Education Software

7. Entertainment software

Application software:• a set of one or more programs designed to solve a specific

problem or do a specific task.• e.g. inventory management, preparation of tax return,

banking, hospital administration, insurance. 1. Word-Processing Software

enables the user to create, edit, view, format, store, retrieve and print documents (written material such as letters, reports, books, etc.) on a computer system.

2. Spreadsheet Software• a numeric data analysis tool that allows user to create a

kind of computerized ledger. • can hold large information and perform calculation just like

calculator.

3. Database Software • a set of one or more programs that enables users to

create a database, maintain it (add, delete and update its records), organize its data in desired fashion and to selectively retrieve useful information from it.

4. Graphics Software • used for creating, editing, viewing, storing, retrieving

and printing designs, drawings, pictures, graphs and anything else that can be drawn in the traditional manner.

5. Personal Assistance Software storing and retrieving personal information, planning

and managing schedules, contacts, financial and inventory of important items

6. Education Software• teaching and learning tool• Black-board, on-line examinations, Authoring tools,

Vocabulary Builder, Mathematics, Geometry, etc7. Entertainment software • Video games, interactive television, game partner,

etc.

Functions of system software

• Controls all operations required to move data into and out of a computer

• Supports development & execution of other applications software

• Monitors effective use of various hardware resources- CPU, Memory & other peripherals

• Communicates with & controls operation of I/O devices

System Software

Categories of system softwareSystem Management Programs• Responsible for mgt &

accurate functioning of computer system

• Manage operations of processor, control I/O, manage storage resources, provide various support devices

• Include1. Operating System

2. Device Drivers

3. System Utilities

System Development Programs• Associated with development

of Computer program• Allow programmers to write &

construct programs that OS can execute

• Include: 1. Programming Languages

2. Language processors

3. Linkers

4. Loader

Operating System• An operating system is a collection of programs that

supervises all the operations of a computer• manages resources of computer system, s.a. memory,

processor, & input/output devices• keeps track of status of each resource & decides who will

have a control over computer resources, for how long & when

• acts as an interface between users & hardware of a computer system

• called platform, coordinates all activities among computer hardware resources

• booting the system: OS loaded from hard disk or floppy disk

Operating System

An operating system is made up of 3 elements:

1. Control programs: provide automatic control of the resources of a computer, like I/O, scheduling, communicating with the operator, and handling interrupts.

2.  Processing programs: called (or invoked) as required by the control programs, e.g. language processors such as compilers and interpreters.

3. Data management programs: control the organisation and access of data used by application programs.

Operating System Functions1. Process management

2. File and software management

3. I/O and peripherals management

4. Memory management

5. CPU Time management

6. Security management

7. Command interpretation

Operating System Functions1.Process management:• creation & deletion of processes, scheduling of system resources, synchronising of processes

1.File and software management: OS stores & retrieves files of data

• supports a large library of typical user programs & files• retrieves the program required by the user from disk and bring it to the main memory to be used by the operator

2.  I/O and peripherals management: • contains peripheral device handlers• configures new devices•Coordination & assignment of different I/O resources while one or more programs is being executed

Operating System Functions 3.  Memory management: • determine how much usable RAM a computer has• decides how this RAM is used• Supervises transfer of data and programs into and out of

RAM

 4.  CPU Time management: • Schedules CPU time so that it can be used effectively• When the CPU is idle (e.g., during I/O operations), the

operating system can give the CPU something to do.

Operating System Functions5. Security management: • provides security features which enable different users to

protect their files• Enforce security/confidentiality through usernames,

passwords, access rights, etc.

6. Command interpretation:• Interpretation of commands & instructions• Coordination & assignment of compilers, assemblers,

utility program & other s/w to various users of computer system

Types of OS

1. Multiprogramming OS

2. Multitasking OS

3. Multiprocessing OS

4. Multithreading OS

5. Multiuser OS

6. Real time OS

Multiprogramming Operating System

• interleaved execution of two or more different and independent programs by same computer

• processor executes each program for a very short interval of time, say, about 150 milliseconds, & then executes the next program in the queue

• All programs residing in main memory will be in one of the 3 states: running (using CPU), blocked (I/O operation being done) & ready (waiting for CPU)

• even though many programs may reside in the computer's memory at the same time, only one program is being executed (running state) at any given time.

• Multiprogramming ensures maximum utilization of CPU, as its never idle

• For multiprogramming to work satisfactorily, large memories are required.

• UNIX, Windows NT, LINUX

Multiprogramming Operating system

Multi tasking Operating System

• System’s capability to concurrently work on more than one task in single user systems

• Technically same as multi programming

• Term Multi programming is used for multi user systems

• Windows 95, 98, 2000, XP, Vista, Windows7,etc

Multiprocessing operating systems

• two or more independent processors are linked together.

• the instructions from different programs can be processed at the same time by different processors

• Simultaneous execution of two or more processes

• Two types: Tightly coupled (single system wide primary memory shared by all processors & Loosely coupled (each processor has own local memory, geographically scattered)

• Multitasking operating system supports two or more active processes simultaneously in a single user system. 

• Multiprogramming operating system supports multiple concurrent process & allows the instruction and data from two or more separate processes to reside in primary memory simultaneously.

• Multiprogramming implies multiprocessing or multitasking operation, but multitasking does not imply multiprogramming.

Multi threading OS

• Basic unit of CPU utilization is a thread, also called light weight process

• Each thread of a process share the same address space, same global variables, same

set of OS resource

• Resource sharing is more efficient, lesser overheads are involved.

• At a particular time thread can be in one of 4 states: running, blocked, ready or terminated

• allows simultaneous access to a computer system through two or more terminals

• associated with multiprogramming

• e.g., dedicated transaction processing system such as railway reservation system with hundreds of terminals under control of a single program

Multi-user operating system

Real Time Operating System

• used in environments where a large number of events mostly external to computer systems, must be accepted and processed in a short time or within certain deadlines.

• e.g. flight control, nuclear reactor control systems, real time simulations, military applications, etc.

• A primary objective of real-time system is to provide quick response times. 

Real Time Operating System• User convenience and resource utilization are of

secondary concern to real-time system. 

• each process is assigned a certain level of priority according to the relative importance of the event processes.

• processor is allocated to the highest priority process among those which are ready to execute. 

• Higher priority process usually pre-empt execution of lower priority processes (called, priority based pre- emptive scheduling)

Device Drivers• Responsible for proper functioning of devices

• Every hardware has a driver program for support, most OS include various h/w drivers

• Acts as translator b/w device & programs that use device

• Not independent programs, assist & are assisted by the OS for proper functioning of device

Utility Programs

• performs a maintenance tasks, usually related to managing system resources e.g. managing disk drive, printer and other devices

• Support, enhance, expand & secure existing programs & data in computer system

• Bundled along with OS

Utility ProgramsMost common utilities include:1. Disk formatting: formatting hard disk in tracks, sectors

for orderly sorting of data2. Disk defragmenter: reorganizing files in a sequential

order & release unused space so that programs run faster

3. Data Compression: squeeze out slack space generated by formatting schemes

4. Back up utility: copies selected files or entire hard disk into another storage medium

5. Data Recovery: recover files or information that is accidentally deleted

6. Disc scanner: Scanning the computer for unnecessary files such as virus and errors

System Development software

• Programming Languages

• Language Processors

• Linkers

• Loader

Programming Languages

• Meaning of programming language

• Types of programming language– Low Level Languages and High Level Languages– Low Level languages-Machine language and

Assembly language.

• differentiate between different types of language giving relative advantages and disadvantages

Language processors

• assembler, compiler, interpreter

• distinguish between compiler and interpreter

Programming languages• Interface of programmer with a computer• Series of commands which are used in development of s/w• Classification

1. Machine language• First generation language• Understood by computer w/o using translation program• Written as strings of binary 1s & 0s• Converted immediately by computer circuitry into electrical

signals required to execute them• Each model of computer has unique machine language• Advantages: fast execution of programs, no translation

required• Used for complex applications s.a. Space control system,

nuclear reactors, chemical processing• Disadvantages: machine dependent, complex language,

difficult to read & understand, error prone, difficult to modify

1. Assembly language• Allows instructions & storage locations to be represented by

mnemonics e.g. ADD, SUB, MLT, etc• Low level language, second generation language, developed by IBM

in 1950sAdvantages: easier to understand & use, easier to locate & correct

errors, easier to modifyLimitations: machine dependent, knowledge of h/w required, machine

level coding2. High level language

• Problem oriented instead of machine based• English words & math notation• 3GL (COBOL, FORTRAN, BASIC, C), 4GL (SQL, QBE), 5GL(LISP,

ProLog)Advantages: readability, machine independent, easy debugging, easy

documentation, faster & low cost development of programsDisadvantages: poor control on h/w, no need for h/w knowledge, less

efficient, more computation time

Programming Language processors

• Transform instructions prepared by programmers using convenient programming language into a form that can be interpreted & executed by a computer system

• three categories:

1. Assembler

• Converts assembly language program into its equivalent machine language program

Programming Language processors

2. Compiler

• Converts the entire source program into object code before program is executed

• Reports all errors of programs along with line numbers, then program is recompiled

• Object program made available & compiler is no longer required memory

• e.g. FORTRAN, C, JAVA compilers

Programming Language processors

3. Interpreter

• Translate one source instruction into object code & computer immediately executes that instruction before moving on to translate next instruction

• Longer time for complete execution than compiled program

• Error can be traced exactly

• Unnecessary usage of memory, interpreter must be always present in the memory

• e.g. BASIC, LISP are interpreted language

Basis• Object Code

• Translation process

• Debugging• Implementation

• Execution

Interpreter• No object code file

• Translates source code line wise

• Debugging easier• Easier to write, less

complex prog• Less memory

required for execution

• slow execution as each statement translated

Compiler• Separate object

code provided• Converts entire

prog into machine code at one go

• Slow debugging• Complex

programs• More memory

required to execute

• Faster execution as object file saved

Linker

• Links compiled module & data files to create an executable program

Loader

• Brings an executable file (code of program) residing on disk into memory for execution

• Automatically invoked during program run

Acquiring software

• Ready to use/Prewritten software• Customised • Tailor made

– In-house development: – Outsourcing:– In-house Vs. Outsourcing

• Public domain software– shareware – freeware

Unit 3. Information System

• Meaning

• Need of an efficient Information System

• Types of Information System

• Information requirement for Planning, Coordination, and Control for various levels in Business, Industry.

• Basic of data arrangement and access

• Meaning and comparison of data, information and knowledge– Need of efficient information- accurate, timely, complete,

precise & relevant– Enhance value of information- form, time, place and

usage utility,– Types of information- strategic, tactical, operational,

statutory

• Meaning and Need of an efficient information System- facilitate acquisition , transformation & distribution of efficient information, improve decision making, performance, productivity and enhance profitability,

Type of Information system• Based on decision making

– Executive Support system– Management information system– Decision Support system– Transaction Processing system– office automation system– expert system.

• Based on organizational level– Strategic level information system– management level information system– operational level information system– knowledge level information system

Executive Support/Information System

• generate strategic information and are used by the top level managers

• lay more emphasis on presentation of summary information, integration of internal and external information, exception reporting techniques and establish link with basic operations of the enterprise

• help in identifying options, evaluation of alternative scenarios and making informed choices regarding the business options.

Decision Support System

• used by managers at middle level for generating tactical information

• DSS not only take input from TPS but from external sources

• They also offer tools for analyzing the information more rigorously and help in generating tactical information and performing 'what - if analysis' for managers.

Comparing Characteristics of MIS and DSSManagement Information Systems (MIS)• 1. The main impact has been on structured tasks, where standard operating

procedures, decision rules, and information flows can be reliably predefined.• 2. The main payoff has been in improving efficiency by reducing costs, turnaround

time, and so on, and by replacing clerical personnel or increasing their productivity.• 3. The relevance for managers decision making has mainly been indirect (e.g., by

providing reports and access to data).• 4, MIS application is routine and done periodically.Decision Support Systems (DSS)• 1. The impact is on decisions in which there is sufficient structure for computer and

analytic aids to be of value but .where the manager's judgment is essential.• 2. The payoff is in extending the range and capability of managers' decision

processes to help them improve their effectiveness.• 3. The relevance for managers is in the creation of a supportive tool, under their

own control, that does .not attempt to automate the decision process, predefine objectives, or impose solutions.

• 4. DSS applications are non-routine, as needed.

Transaction Processing System (TPS)• refers to a computerized system that serve the operational

level of the organization• Generates operational information.• At the operational level, tasks, resources, and goals are

predefined and highly structured. • records the daily routine transactions necessary to conduct

business and one such transaction affects many databases• Management Information System uses the information

contained in the TPS and processes them for producing the summary reports for managers to plan and control operations.

• TPS is the key producer of information for other types of systems especially the functional information systems.

Expert Systems

• aim at formalizing expertise and make it available for repetitive type of business decisions.

• use artificial intelligence tools to generate knowledge out of the information, existing theories, belief and experiences of managers in various business activities.

• they help human experts perform their job more effectively and replicate the expertise at various locations in the business enterprise.

EIS

DSS AND MIS

TPS

TOP

MIDDLE

LOWER

EIS

DSS AND MIS

TPS

TOP

MIDDLE

LOWER

Expert Systems Office Automation System

Application of IS at different level of management

• Functional point of view- purpose, features and cycle– Financial and accounting information system– Human resource development and management

system– Manufacturing or production information system– Marketing information system

Type of Information system

Accounting information systems

• record and report business transactions and other economic events as well as help in producing financial statements.

Marketing information system

• set of procedures and practices employed in analyzing and assessing marketing information, gathered continuously from sources inside and outside of a firm

• Information requirement for Planning, Coordination, and control for various level in Business, Industry

• Basic of data arrangement and Access– Data arrangement and access for specific

information needs– Data access and their usage

Information requirementFunctions of organisation

Information requirement

Information system required

Planning Strategic ESS

Tactical DSS, MIS

Operational TPS

Basics of data arrangement and Access• Data arrangement- data hierarchy (field, record, file,

etc.)

• Data access typically refers to software and activities related to storing, retrieving, or acting on data housed in a database or other repository.

• There are two types of data access, sequential access and random access.