Fundamentals of Computer

By: Priyanka Mehta

(Assist. Prof. – CS(SU))

Introduction...

Computers are seen in all walks of life and have become anintegral part of most of our daily activities. They are foundin various shapes and sizes.

A typical computer of today, packs in more power, morestorage capacity and much more I/O capability than a typicalcomputer of 1950s, which occupied a big hall.

Although this is the most common form of computer seentoday, there are many applications for which they areinsufficient, such as weather prediction, nuclear simulation,astronomical calculations and bioinformatics, which requiremuch more computing power.

Continued...

Also, there are many tiny and small computers which are

actually hidden or embedded in home appliances, cameras,

mobile phones etc.

Going through this wide variety or diversity of computers, it

is necessary to understand that what is common and what is

different. In other words, it is important to define the

common principle which binds all the different forms of

computer together.

Course Motivation...The knowledge of computer system is useful if we need to:

Design/build a new computer/processor (rare opportunity andless likely – as the number of new architectures developed todayis very small)

Design/build an improved version of a computer/processor (morelikely)

Improve software performance (as hardware influences softwareperformances)

Purchase a computer

Provide a solution with an embedded computer (more designopportunities)

What is Building Architecture...

Building Architecture: Building architecture is basically a

plan or an overall layout that describes the functionalities of

different components of building. A civil engineer takes this

plan and do structural design and makes sure that the built

building is durable, finished and so on.

What is Computer Architecture...

Computer Architecture: Computer architecture is also a

plan of overall functionality of the computer. An electrical

engineer realize this plan and do circuit design by putting

basic components like transistors, registers, capacitors and

so on, together and make sure that all basic operations it can

perform with efficiency.

Definition of Computer...

A computer is a programmable device/machine whichis capable of solving problems and manipulating data.

It accepts data, processes the data by doing somemathematical and logical operations and gives us thedesired output.

Processi

ngInput Output

Continued...

It can accept data.

It can store data.

It can process data asdesired.

It can retrieve thestored data as and whenrequired.

It can print the result inthe desired format

Characteristics of Computer...

Speed: A computer can perform millions (1,000,000) of

instructions and even more per second. And so, the speed of the

computer is determined in terms of microsecond (10-6 part of a

second) or nanosecond (10-9 part of a second). From this we can

imagine how fast the computer performs work.

Accuracy: The degree of accuracy of computer is very high and

every calculation is performed with the same accuracy. The

circuits in a computer have electronic parts which do not have

wear and tear and these circuits can run for years without any

errors. The errors in computer are due to human and inaccurate

data.

Continued...

Diligence: A computer is free from tiredness, lack of

concentration, fatigue etc. It can work for hours without

creating any error. If millions of calculations are to be

performed, a computer will perform every calculation

with the same accuracy. Due to this capability it

overpowers human being in routine type of work.

Versatility: It means that the computer has the capacity

to perform completely different type of work. A

computer can be used to prepare payroll slips or it can

be used for inventory management or to prepare electric

bills.

Continued...

Power of remembering: Computer has the power of storing anyamount of information or data. Any information can be stored andrecalled as long as we require it, for any number of years. Itdepends entirely upon us how much data we want to store in acomputer and when to lose or retrieve these data.

No IQ: Computer is a dumb machine and it cannot do any workwithout instruction from the user. It is up to us what we want todo and in what sequence. So a computer cannot take its owndecision as we can.

Storage: The computer has an in-built memory where it can storea large amount of data. One can also store data in secondarystorage devices, which can be kept outside the computer and canbe carried to other computers.

Functional Units of Computer...

Input Unit: A computer uses input devices for data entry

purposes and accepts the data in a computer readable form. Some

input devices require data to be recorded on an input medium

such as magnetisable material. While others allow direct

communication between the user and the computer such as

keyboards, mouse, touch screen etc.

Output Unit: A computer uses output devices to display the

processes information. These devices take the machine coded

output results from the processor and convert them into a form

that can be used by human beings. Commonly used output

devices are display screen, printers etc.

Continued...

Central Processing Unit: CPU is called the brain of the

computer that carries out the basic arithmetical, logical and

input/output operations of the system. The CPU is placed on a

single silicon chip called a microprocessor. The speed of the CPU

is measured in MHz or GHz. If a processor runs at 1MHz (or

1GHz), then it means that the computer is running at 1,000,000

cycle/sec (or 1,000,000,000 cycles/sec) or this amount of

instructions the computer can carry out in a second. CPU has two

typical components:

Arithmetic & Logic Unit(ALU)

Control Unit (CU)

Continued...

Control Unit (CU): The control unit is the central part of the

CPU that controls and coordinates its operation. It determines

the sequence in which the instructions are executed, interprets

the instructions and issues the control and timing signals to

other units of the computer and coordinates the activities of

computer’s peripheral devices.

Arithmetic & Logic Unit(ALU): The ALU is a digital circuit

that performs arithmetic and logical operations. An ALU loads

data from input registers, an external control unit then tells the

ALU what operation to perform on that data and then the ALU

stores its result into an output register. The CU is responsible

for moving the processed data between these registers, ALU

and memory.

Continued...

Memory Unit: Memory is used to hold instructions and

data to be processed by CPU. There are two types of

memory:

ROM(Read Only Memory): It contains the program

and data that are permanently recorded when the

computer is manufactured. It is read and used by the

processor but cannot be altered by the user.

RAM(Random Access Memory): It contains the data

that are temporarily recorded or erased by the

computer program or the computer user.

Generations of Computers

First Generation Computers (1940-1956) – Vacuum Tubes: Eckert & Mauchly

developed the first electronic computer ENIAC (Electronic Numerical Integrator &

Calculator) in 1946 in the USA.

It used high-speed vacuum tubes as switching devices and had a very small memory.

The ENIAC took about 200 microseconds to add two digits and about 2400

microseconds to multiply.

In 1946, Prof. John V Neumann proposed the concept of stored programming (i.e.

The storage of machine instructions in the memory of the computer along with the

data).

The first commercial production of stored electronic computers was UNIVAC

(UNIVersal Automatic Computer).

During this period, computer programming was mainly done in the machine

language. Assembly language was introduced during the early fifties.

Continued...Its characteristics are:

Computers used vacuum tubes for circuitry and magnetic drums for memory.

Big in size, taking up entire space.

Expensive to operate.

Used great deal of electricity and generated lot of heat.

Used machine language to perform operations

Only one problem can be solved at a time.

Inputs was based on punched cards and paper-tape and output was displayed

on printouts.

ENIAC ‘s main control panel

ENIAC ‘s vacuum tubes in holders Back of ENIAC showing vacuum tubes

Programming ENIAC

Continued...

Second Generation Computers (1956-1963) - Transistors: Second generation

computers emerged around 1959 with the usage of transistors instead of vacuum tubes.

Transistors made of germanium semiconductor material, which were highly reliable as

compared to vacuum tubes.

The switching circuits for computers made from transistors were about 10 times more reliable,

10 times faster, occupied about one-tenth space and were 10 times cheaper when compared

with computers incorporating vacuum tubes.

Another major breakthrough during this period was the invention of magnetic disk for storage.

The higher reliability of computers and large memory availability led to the development of

high-level languages like FORTRAN, COBOL, ALGOL etc.

Good batch-processing operating systems emerged during the second generation.

Commercial applications like Payroll, Inventory Control, Production Planning & General

Ledger systems were developed.

Continued...

Its characteristics are:

Use of transistors allowed computers to become smaller, faster,

cheaper, more energy-efficient and more reliable than first

generation computers.

Generated a great deal of heat that leads to computer damage.

Inputs was based on punched cards and outputs on printouts.

Used assembly language to perform operations by specifying

instructions.

Stored instructions in memory and used magnetic core technology.

Transistor based central processing unit

Transistor Technology

Continued... Third Generation Computers (1964-1971) – Integrated Circuits: The third generation of

computers began in 1964 with germanium transistors being replaced by silicon transistors.

The control circuits comprised small-scale integrated circuits, consisting of transistors,

resistors and capacitors, grown on a single chip of silicon, eliminating wired interconnections

between the components.

Hundreds or even thousands of transistors could be fabricated on a single wafer of silicon. In

addition, these fabricated transistors could be connected to form logic circuits on the same

chip.

In this generation, size of main memory reached about 100Mb.

The combined effects of high memory, powerful CPU and large disk memories led to the

development of time-shared operating systems.

High level languages like FORTRAN IV, COBOL-68, PL/1 were developed.

Many important on-line systems like air-line reservation, dynamic production control,

integrated DBMS emerged.

Continued...

Its characteristics are:

Transistors were miniaturized and placed on silicon

chips called semiconductors, which increased the speed

and efficiency.

Inputs were given through keyboards and outputs were

displayed on monitors which were interfaced through

Operating system.

Run multiple applications at a time.

Continued... Fourth Generation Computers (1971-present) - Microprocessors: The fourth

generation of computers emerged with the Large Scale Integrated Circuits

(LSIc) and Very Large Scale Integrated Circuits (VLSIs) which packed about

50,000 transistors in a single chip. The advent of microprocessors led to two

distinct advancements in computer development:

One advancement was the development of personal computers through

which costs came down rapidly. Floppy disk served as a low cost, high

capacity backup peripherals.

The other advancement of development was the decentralization of

computer organization. Individual microprocessor controlled the terminals

and peripheral devices which allowed the CPU to concentrate on processing

activities. Disk memory became very large.

Continued...

Its characteristics are:

Thousands of ICs were built on a single

silicon chip.

These small computers can be linked

together to form a network, which

eventually led to the development of

internet.

Development of GUIs, mouse and

handheld devices.

Continued... Fifth Generation Computers (Present-

beyond) – Artificial Intelligence:

Computer scientists and engineers are

now talking about developing fifth

generation computers that can think.

The emphasis is now shifting from

developing reliable, faster and smaller

but dumb machines to more intelligent

machines. An effective fifth-generation

computer would be highly complex and

intelligent electronic device conceived

with the idea of intelligence (called

artificial intelligence).

Types of Computers

According to size and functioning computers

may be classified as:

Micro Computers

Mini Computers

Mainframe Computers

Super Computers

Micro Computers The microcomputer originated in late 1970s. The first microcomputers

were built with 8-bit microprocessor chips. Eg: Zilog Z80, MOS 6502,

Intel 8080 and MC 6809.

A microcomputer is based on a microprocessor chip as CPU. It consists

of a microprocessor , a semiconductor, ROM for storing program and a

RAM for processing the data.

They are designed for use by one person at a time. So, they are single-

user machines.

They are characterized by minimum speed and storage capacity.

Eg: IBM PC, Laptops, Notebook Computers, Palm Tops, Smart

Phones, Programmable Calculator.

Mini Computers A minicomputer is a small general-purpose computer that has

computing power larger than that of microcomputers.

It supports more than one user at a time and used in multi-user system

in which various users can work at a time.

This type of computer is generally used for processing large volume of

data in an organization.

They have a wordlength of 16 bits or more.

They can be used as servers in Local Area Network (LAN).

Eg: SPARC, POWER, ITANIUM etc.

Mainframes Computers The mainframe computers have wordlength of 32bits, 48bits, or

64bits.

They can support more than 100 users in timesharing mode and

can have a wide variety of languages and efficient OS.

They operate at a very high speed, have very large storage

capacity and can handle the work load of many users.

They are generally used in centralized databases or used as

controlling nodes in Wide Area Network (WAN).

Eg: DEC, ICL and IBM 3000 series.

Super Computers Super computers are characterized by very large size and very

high processing speeds and generally used for complex scientific

applications.

They are the most powerful and very expensive.

The work done by 40,000 IBM personal computers can be easily

done with the help of one super-computer.

They are mainly used for weather forecasting, remote sensing,

image processing, bio-medical applications etc.

Eg: CRAY XMP, CRAY 2, PARAM (India)