Evolution of Computers

The growth of the computer industry started with the need for performing fast calculations.

Some early calculating devices are:

Abacus: It was discovered in around 3000 BC. It consisted of beads on movable rods divided

into two parts. Addition and multiplications of numbers was done by using the place value of

digits of the numbers and position of beads in an abacus.

Napier’s Logs and Bones: The idea of logarithm was developed by John Napier in 1617. He

devised a set of numbering rods known as Napier’s bones through which both multiplication

and division could be performed.

Pascaline: Blaise Pascal, a French mathematician invented an adding machine in 1642 that

was made up of gears. It was used for addition and subtraction of numbers.

Leibnitz’s Calculator: In 1673, Gottfried, a German mathematician extended the capabilities

of the adding machine invented by Pascal to perform multiplication and division.

Jacquard’s Loom: Joseph Jacquard devised punch cards and used them to control loom in

1801.

Difference Engine and Analytical Engine: Charles Babbage, an English mathematician

developed a machine called Difference Engine. Later, he designed the Analytical Engine

which used the basis of modern computer. It included the concept of central processor,

memory storage and input-output devices. Even the stored information could be modified. It

could perform all the four arithmetic operators.

Babbage established the basic principles on which today’s modern computer work,

therefore, this earned him the title of ‘Father of Modern Computers’.

Mark I: In 1944 Howard Aiken developed an electromechanical machine called Mark I

which could multiply two 10 digits numbers in 5 seconds.

John Von Neuman: In 1945, he proposed the concept of stored program computer.

According to him, the processor executes the instructions stored in the memory of the

computer. Since, there is only one communication channel, the processor at a time can either

fetch data or an instruction. This limitation is known as Von Neumann bottleneck.

EDVAC: Electronic Discrete Variable Automatic Computer was the first stored program

computer developed in 1952.

ENIAC: Electronic Numerical Integrator And Calculator was the first electronic

computer developed.

Generation of computers

The computer generation is categorized by the technology used.

The First Generation (1942-55)

Salient features of First generation computers are:

Used vacuum tubes to control and amplify electronic signals.

Huge computers and occupy lot of space.

High electricity consumption and high heat generation

Not reliable and prone to frequent hardware failure

Very costly and require frequent maintenance

Require air conditioning environment

Commercial production was difficult

Programming was done in machine language. The Assembly language stared at the

end of this generation.

Examples: ENIAC, EDVAC, UNIVAC - I

The Second Generation (1955-64)

Salient features of Second generation computers are:

Used transistors

Smaller in size and less expensive

Consumed less electricity and emitted less heat

Magnetic core memory and magnetic disk were used

First operating system developed

Require air conditioning environment

Programming in Assembly language. The High-level language stared at the end of

this generation.

Wider commercial use but commercial production was difficult.

Examples: IBM - 1401, IBM 1620, UNIVAC 1108

The Third Generation (1964-75)

Salient features of Third generation computers are:

Use integrated circuits

Smaller in size, faster and more reliable

Low power consumption and less emission of heat

Example: IBM 360 series

The Fourth Generation (1975 onwards)

Salient features of Fourth generation computers are:

ICs with LSI and VLSI technology

Microprocessor developed

Portable computer developed

Networking and data communication became popular

Different types of secondary memory with high storage capacity and fast access

developed.

Very reliable, powerful and small size

Negligible power consumption and heat generation

Very less production cost

The Fifth Generation

Salient features of Fifth generation computers are:

Parallel processing: Many processors are grouped together

Superconductivity: To develop devices that respond to human languages and will

have the ability to apply previously gained knowledge to execute a task

Artificial Intelligence : Make the decision to execute a task

Example: Voice recognition, Visual recognition etc.

Hardware Concepts

A computer is an electronic device that processes input data and produces result (output)

according to a set of instructions called program.

Data: It is the term used for raw facts and figures. For example, 134, 9, ‘Raju’, ‘C’ etc.

Information: Data represented in useful and meaningful form is called information. For

example, Raju is 9 years old is and information.

A computer performs basically five major functions irrespective of its size and make.

It accepts data or instructions by way of input (Input Unit)

It stores data(Memory)

It processes data as required by the user (Central Processing Unit - ALU)

Central Processing

Unit (CPU)

Arithmetic & Logical

Unit (ALU)

Control Unit (CU)

Memory Registers

Cache

Memory

Secondary Storage E.g, Hard Disk, Floppy Disk

Removable Tertiary Media :

Compact Disk, Magnetic Tape, Digital

Versatile Disk (DVD) USB Drive,

Memory cards

Output Unit

E.g.

Monitor/Visual

Display Unit

(VDU), LCD

screen, Television,

Printer (Dot

Matrix

Printer, Desk jet/

Inkjet/ Bubble jet

Printer, Laser

Printer), Plotter,

Input Unit

E.g. Keyboard,

Mouse, Light pen,

Touch Screens,

Graphics Tablets,

Joystick,

Microphone,

OCR, Scanner,

Smart Card reader,

Barcode reader,

Biometric sensor,

web camera

Main Memory

(RAM and ROM)

It controls operations of a computer (Central Processing Unit - Control Unit)

It gives results in the form of output (Output Unit)

Hardware is the physical tangible parts of computer

Input Unit: It takes the input and converts it into binary form so that it is understood by the

computer.

Central Processing Unit / Microprocessor It is a processor on a single chip. It is the brain of

a computer. CPU consists of two parts: Control Unit (CU) and Arithmetic Logic Unit (ALU)

ALU performs all arithmetic and logical operations. CU controls all other components and

activities of the computer.

Memory Registers A register is a temporary unit of memory in the CPU. This receives

data/information and then this data/information is held as per requirement. Each register in

CPU has a specific function.

Output Unit: It re-converts the binary signal to be understood by human beings.

Communication Bus: A Bus is a subsystem that transfers data and instructions between

functional components of a computer or between different computers. Buses can be Parallel

Buses, which carry data words in parallel on multiple wires, and Serial Buses, which carry

data in bit-serial form. Buses are of three types.

1. The Address Bus carries a number called memory address that indicates the desired

location of data.

2. The bidirectional Data Bus, transfers data and instructions (reads or writes the data)

3. A Control Bus is used to direct and monitor the actions of the other functional

components of computer.

Concept of Booting: When a computer is switched on, a copy of boot program is brought

from ROM into the main memory. The process is called booting. The CPU first runs the jump

instruction that transfers to BIOS (Basic Input Output System) and it starts executing. The

BIOS conducts a series of self-diagnostic test called POST (Power on Self-Test). Thereafter

the BIOS locate a bootable drive to load the boot sector. The execution is then transferred to

the Boot Strap Loader program on the boot sector which loads and executes the operating

system.

Booting process is of two types – Warm and Cold

Cold Booting: When the system starts from initial state i.e., it is switched on (Power button

is pressed), we call it cold booting or hard booting.

Warm booting: When the system restarts or reset button is pressed, we call it warm booting

or soft booting. The system does not start from initial state and so all diagnostic tests need not

be carried out.

Classification of Computer

The computers can be classified based on the technology being used as: Digital, Analog and

Hybrid

Digital Computers: These computers are capable of processing information in discrete form

i.e., 0 and 1.

Analog Computers: These computers works on continuously changeable aspects of physical

phenomenon such as pressure, mechanical motion and electrical quantities.

Hybrid Computers: These computers use both analog and digital technology. It has the

speed of analog computer and the accuracy of digital computer.

Classification of Digital Computers

Micro Computers: Also known as Personal Computers. It uses a entire CPU on single chip

called microprocessor.

Mini Computers: These computers can support multiple users working simultaneously on

the same machine.

Main Frame: These computers are large and very powerful computers with very high

memory capacity. These can process huge databases such as census at extremely fast rate.

Super Computers: These are fastest and very expensive computers. They can execute

billions of instructions per second. These are multiprocessor, parallel systems suitable for

huge amounts of mathematical calculations.

The main difference between a supercomputer and mainframe is that a supercomputer

executes fewer programs as fast as possible whereas a mainframe executes many programs

concurrently.

Internal Storage encoding of Characters

ASCII: It stands for American Standard Code for Information Interchange. ASCII-7

represents 128 characters. ASCII – 8 represents 256 characters.

ISCII: It stands for Indian Standard Code for Information Interchange. It is a 8 bit code

which allow Indian script alphabets to be used.

Unicode: It is a new universal coding standard adopted by all new platforms. It provides a

unique number for every character irrespective of the platform, program and the language.

Microprocessor: The entire CPU on single chip.

Characteristics of Microprocessor

Instruction Set: It is a set of instructions that the microprocessor executes.

Word Length: The number of bits processed in a single instruction is called word length or

word size. The word size is directly proportional to the processing power of CPU. The 64 bit

processor is two times faster than 32 bit processor.

System Clock speed: The microprocessor’s pace is controlled by the system clock. The

system clock generates pulses which are measured in million of cycles per second (MHz).

The number of pulses generated by the clock per unit of time is its clock speed. Each

microprocessor is characterized by its clock speed.

Classification of Microprocessors

RISC: It stands for Reduced Instruction Set Computer. It is a type of microprocessor

architecture that uses a small set of instructions of uniform length.

CISC: It stands for Complex Instruction Set Computer. A CISC chip such as Intel Pentium

provides programmers with hundreds of Instructions of variable sizes.

EPIC: It stands for Explicitly Parallel Instruction Computing. It is a computer architecture

that combines the best features of RISC and CISC. For example, Intel’s 64 bit processor

based on EPIC.

Memory Units: Bit (Binary Digit) / Byte (KiloByte, MegaByte, GigaByte, TeraByte,

PetaByte, ExaByte, ZettaByte, YottaByte)

The elementary unit of memory is a bit. A group of 4 bits is called a nibble and a group of 8

bits is called a byte. One byte is the minimum space required to store one character.

1 Byte = 8 bits

1 KiloByte (KB) = 1024 Bytes

1 MegaByte(MB) = 1024 x 1024 Bytes = 1024 KB

1 GigaByte(GB) = 1024 x 1024 x 1024 Bytes = 1024 MB

1 TeraByte(TB) = 1024 x 1024 x 1024 x 1024 Bytes = 1024 GB

1 PetaByte(PB) = 1024 x 1024 x 1024 x 1024 x 1024 Bytes = 1024 TB

1 ExaByte(EB) = 1024 x 1024 x 1024 x 1024 x 1024 x 1024Bytes = 1024 PB

1 ZettaByte(ZB) = 1024 x 1024 x 1024 x 1024 x 1024 x 1024 x 1024 Bytes = 1024 EB

1 YottaByte(YB) = 1024 x 1024 x 1024 x 1024 x 1024 x 1024 x 1024 x 1024 Bytes = 1024 ZB

Primary and Secondary Memory

The computer memories can be divided into following categories:

Primary Memory

Secondary Memory

Cache Memory

Main Memory (Primary storage or Internal Memory): It is directly accessible to the CPU.

It is of two types RAM & ROM

RAM ROM

Random Access Memory is used for

primary storage in computers to hold active

information of data and instructions.

Read Only Memory is used to store the

instructions provided by the manufacturer to

check basic hardware and to load operating

system from appropriate storage device.

It is a temporary memory. The data or

instructions are lost when electricity goes

off. It is also called as volatile memory.

It is a permanent memory. The data and

instructions are retained even when electricity

goes off. It is also called as non - volatile

memory.

Examples: DDR1 SDRAM, DDR2

SDRAM, DDR3 SDRAM (Double data

Examples: PROM (programmable) ,

EPROM (erasable programmable),

rate synchronous dynamic random

access memory)

EEPROM

(Electrically Erasable Programmable )

RAM can be classified into two categories:

Dynamic RAM: The data stored is refreshed continuously and this consumes a lot of

processor time.

Static RAM: It is faster because it is made up of flip flops to store data and these flip flops

do not require any refreshing.

ROM is available in various forms:

PROM: Once it is programmed, it cannot be changed.

EPROM: The content can be erased by exposing in ultraviolet light and it can be

programmed.

EEPROM: The content can be erased using electric signals and it can be programmed.

Cache Memory: It is a special high speed memory. it is used to hold frequently accessed

data and instructions. Whenever some data is required, the CPU first looks into cache. If data

is found, we call it a cache hit and the information is transferred to the CPU. In case of a

miss, the main memory is accessed. There are two types of cache memory:

L1 cache: It is small and is built inside the CPU. It is fast as compared to L2 cache.

L2 cache: It is large but slower and is mounted on the motherboard.

Secondary Memory

Secondary Storage Devices: (External Memory) differs from primary storage in that it is not

directly accessible by the CPU. The computer usually uses its input/output channels to access

secondary storage and transfers the desired data in primary storage. Secondary storage does

not lose the data when the device is powered down—it is non-volatile.

1. Magnetic storage uses different patterns of magnetization on a magnetically coated

surface to store information. Magnetic storage is non-volatile. The information is

accessed using one or more read/write heads which may contain one or more recording

transducers.

Hard disk drive, used for secondary storage

Floppy disk, used for off-line storage

Magnetic tape data storage, used for tertiary and off-line storage

2. Optical storage, The information is stored and read using a laser beam. The data is

stored as a spiral pattern of pits and ridges denoting binary 0 and 1. Examples are CD

and DVD.

Compact Disk: It stores app. 700MB of data. There are three types of CDs.

CD-ROM: It stands for Compact Disk – Read Only Memory and data is written on

these disks at the time of manufacture. This data cannot be changed but only read.

CD-R: It stands for Compact Disk- Recordable. Data can be recorded but only once.

After that data cannot be modified or erased.

CD-RW: It stands for Compact Disk – Rewritable. It can be read or written multiple

times.

DVD: It stands for Digital Versatile Disk or Digital Video Disk. It stores 4.7GB of data

It comes in three variations: DVD-ROM, DVD – R, DVD – RW

Blu-Ray Disk: It stores up to 25GB of data. The CDs and DVDs use red laser beam

whereas blue ray disk uses a blue laser to read/write data on a disk.

3. Solid State Memories: The term solid state means no moving parts. It based on

electronic circuits with no moving parts.

Pen Drive or Flash Drive can be repeatedly erased and written using electric signals. A flash drive consists of a small printed circuit board carrying the circuit elements and

a USB connector, insulated electrically and protected inside a plastic, metal, or

rubberized case which can be carried in a pocket or on a key chain, Most USB flash

drives draw their power from the USB connection, and do not require a battery.

Input / Output Ports and Connections:

Communication Ports (Input / Output Ports): Used to connect various peripherals (devices)

to the computer

1. Serial Port: It transfers data serially 1 bit at a time. It comes in the form of 9 pin or 25

pins male connector. It is used to connect devices like mouse and modem.

2. Parallel Port: It can send or receive a byte (8 bits) at a time. The 8 bits are transferred

parallel to each other. It comes in the form of 25 pin female connector. It is used to

connect devices like printer, scanner, and external hard disk CD writer, zip drive, tape

backup drive, etc.

3. USB (Universal Serial Bus) : It is

intended to replace many varieties

of serial and parallel ports. It is used to

connect to various devices like printers,

scanners, mice, joystick, digital

camera, web cameras, speakers,

telephones, zip drives, network

connections, scientific data acquisition

devices, etc.

4. PS-2 Port (Personal System-2): It is used to connect keyboard (purple

coloured port) or mouse (green

coloured port).

5. Bluetooth: Bluetooth is an open

wireless technology standard for

exchanging data over short distances

creating personal area networks

(PANs) with high levels of security.

Bluetooth is a standard for a small,

cheap radio chip to be plugged into

computers, printers, mobile phones, etc

6. Infrared Port: The data is

transmitted through infrared. The

remote control of TV set uses the same

technology.

7. Firewire Port: This port is used

to transfer data rapidly from one

electronic device to another. It has the

ability to interact with a number of different devices since it provides a single plug and

socket connection for all devices. The data transfer is faster than USB port.