Unit-1
Lecture-1
Function Unit of Digital System and Their Interconnections
Computer has become a part and parcel of our daily lives, we cannot disagree to this fact we see
computers everywhere that is some kind of processing unit say, a laptop which we use in our daily
life, tablets, mobile phones which are used by one and all today and intelligent appliances like
smartphone, smart watch and various other appliances.
So, we need to understand,
how a computer actually works?
what is there inside a computer?
So here these two terms computer architecture and computer organization will be taken care.
what is computer architecture?
what is computer organization?
Computer Architecture is a functional description of requirements and design implementation for
the various parts of a computer. It deals with the functional behaviour of computer systems. It
comes before the computer organization while designing a computer.
Architecture describes what the computer does.
Computer Organization comes after the decision of Computer Architecture first. Computer
Organization is how operational attributes are linked together and contribute to realizing the
architectural specification. Computer Organization deals with a structural relationship.
The organization describes how it does it.
Computer architecture consists of those attributes of the system that are visible to the programmer by
this what we mean is how the various components of a computer system are integrated to achieve the
desired level of performance
Computer Organization consists of the design of components and functional blocks using which
computer systems are built comes to the organizational part.
Example:
Think of an architect who does who plans the entire design of your house, the map, the floor mapping
etc.
The civil engineers who actually does the exact building like what kind of construction will be taken
care of, how the construction will be taken care of, how much percentage of cement bricks will be
there are.
Difference between Computer Architecture and Computer Organization:
SNo.
1
2
3
Computer Architecture
Architecture describes what the computer
does.
Computer Architecture deals with the
functional behaviour of computer systems.
In the above figure, it’s clear that it deals
with high-level design issues.
4
5
6
7
8
Architecture indicates its hardware.
For designing a computer, its architecture
is fixed first.
Computer Architecture is also called
Instruction Set Architecture (ISA).
Computer Architecture comprises logical
functions such as instruction sets,
registers, data types, and addressing
modes.
The different architectural categories
found in our computer systems are as
follows:
1. Von-Neumann Architecture
2. Harvard Architecture
3. Instruction Set Architecture
4. Micro-architecture
System Design
9
10
It makes the computer’s hardware visible.
Architecture coordinates the hardware
and software of the system.
11
The software developer is aware of it.
Computer Organization
The Organization describes how it does it.
Computer Organization deals with a
structural relationship.
In the above figure, it’s also clear that it
deals with low-level design issues.
Where Organization indicates its
performance.
For designing a computer, an organization is
decided after its architecture.
Computer Organization is frequently called
microarchitecture.
Computer Organization consists of physical
units like circuit designs, peripherals, and
adders.
CPU organization is classified into three
categories based on the number of address
fields:
1. Organization of a single
Accumulator.
2. Organization of general
registers
Stack organization
It offers details on how well the computer
performs.
Computer Organization handles the
segments of the network in a system.
It escapes the software programmer’s
detection.
Evolution of Computer:
“Whenever there is a need for doing certain things then only something comes up”
Constant quest of building automatic computing machines has driven the development of computers.
So in initial efforts some mechanical devices like pulleys, levers, gears they were built during world
war II Mechanical relays were used to perform some kind of computation like using small relays
people design circuits to carry out the operations then comes vacuum tubes where the first electronic
computer called ENIAC was developed and from then semiconductor transistors were developed
when semiconductor transistors came into picture then the journey of miniaturization started first with
small scale integration then people moved with medium scale integration then large scale integration
then to very large scale integration and now the era of ultra large scale integration where we stand
today.
SSI -> MSI -> LSI -> VLSI -> ULSI ->Billions of transistors per chip
The first mechanical calculator that was invented by b pascal so this particular calculator could add
only two numbers, it can only add two numbers or it can only subtract two numbers and if you wanted
to do multiplication and division it could have been done by repeated addition or repeated subtraction.
Computer Generations
Zeroth Generation-
Mechanical Computers (1642-1945)
First Generation-
Vacuum Tubes (1945-55)
Second Generation- Transistors (1955-65)
Third Generation –
Integrated Circuits (1965-1980)
Fourth Generation - Very Large-Scale Integration (1980-1990)
Fifth Generation –
Ultra Large-Scale Integration (1990- Till date)
The development of computer systems is normally discussed as the development over different
generations.
With the succession of different generations, came the advancement in computer technology.
Let us now discuss the development in Computer Technology over the different generations.
Zeroth Generation
In 1642, Blaise Pascal (French mathematician, physicist, philosopher) invented a mechanical
calculator called the Pascaline
In 1671, Gottfried von Leibniz (German mathematician, philosopher) extended the Pascaline to do
multiplications, divisions, square roots:
Drawback: None of these machines had memory, and they required human involvement at each
step.
First Generation
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The period 1940 to 1956, roughly considered as the First Generation of Computer.
The first generation computers were developed by using vacuum tube or thermionic
valve machine.
The input of this system was based on punched cards and paper tape; however, the
output was displayed on printouts.
The first generation computers worked on binary-coded concept (i.e., language of 01). Examples: ENIAC, EDVAC, etc.
Second Generation
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The period 1956 to 1963 is roughly considered as the period of Second Generation of
Computers.
The second generation computers were developed by using transistor technology.
In comparison to the first generation, the size of second generation was smaller.
In comparison to computers of the first generation, the computing time taken by the
computers of the second generation was lesser.
Third Generation
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The period 1963 to 1971 is roughly considered as the period of Third Generation of
computers.
The third generation computers were developed by using the Integrated Circuit (IC)
technology.
In comparison to the computers of the second generation, the size of the computers of
the third generation was smaller.
In comparison to the computers of the second generation, the computing time taken by
the computers of the third generation was lesser.
The third generation computer consumed less power and also generated less heat.
The maintenance cost of the computers in the third generation was also low.
The computer system of the computers of the third generation was easier for
commercial use.
Fourth Generation
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The period 1972 to 2010 is roughly considered as the fourth generation of computers.
The fourth generation computers were developed by using microprocessor technology.
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By coming to fourth generation, computer became very small in size, it became
portable.
The machine of fourth generation started generating very low amount of heat.
It is much faster and accuracy became more reliable.
The production cost reduced to very low in comparison to the previous generation.
It became available for the common people as well.
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Fifth Generation
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The period 2010 to till date and beyond, roughly considered as the period of fifth
generation of computers.
By the time, the computer generation was being categorized on the basis of hardware
only, but the fifth generation technology also included software.
The computers of the fifth generation had high capability and large memory capacity.
Working with computers of this generation was fast and multiple tasks could be
performed simultaneously.
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Some of the popular advanced technologies of the fifth generation include Artificial
intelligence, Quantum computation, Nanotechnology, Parallel processing, etc.
What is Computer?
COMPUTER: Common Operating Machine Particularly/Purposely Used for Technological/Trade,
Educational and Research.
A computer is a programmable electronic device that accepts raw data as input and processes it with a
set of instructions (a program) to produce the result as output. It renders output just after performing
mathematical and logical operations and can save the output for future use. It can process numerical
as well as non-numerical calculations. The term "computer" is derived from the Latin word "computare"
which means to calculate.
A computer is designed to execute applications and provides a variety of solutions through integrated
hardware and software components. It works with the help of programs and represents the decimal
numbers through a string of binary digits. It also has a memory that stores the data, programs, and
result of processing. The components of a computer such as machinery that includes wires, transistors,
circuits, hard disk are called hardware. Whereas, the programs and data are called software
Functional Units of Digital System
Computer is a processing machine that process the information in digital form i.e. (0’s & 1’s). Means
digital computer can only understand binary language (0’s & 1’s). If any analog quantity is to be
processed, they must be converted into digital form before processing.
A computer consists of five main components namely, Input unit, Central Processing Unit, Memory unit
Arithmetic & logical unit, Control unit and an Output unit.
Input unit
o
Input units are used by the computer to read the data. The most commonly used input devices
are keyboards, mouse, joysticks, trackballs, microphones, etc.
o
However, the most well-known input device is a keyboard. Whenever a key is pressed, the
corresponding letter or digit is automatically translated into its corresponding binary code and
transmitted over a cable to either the memory or the processor.
Central processing unit
o
Central processing unit commonly known as CPU can be referred as an electronic circuitry
within a computer that carries out the instructions given by a computer program by performing
the basic arithmetic, logical, control and input/output (I/O) operations specified by the
instructions.
Memory unit
o
The Memory unit can be referred to as the storage area in which programs are kept which are
running, and that contains data needed by the running programs.
o
The Memory unit can be categorized in two ways namely, primary memory and secondary
memory.
o
It enables a processor to access running execution applications and services that are
temporarily stored in a specific memory location.
o
Primary storage is the fastest memory that operates at electronic speeds. Primary memory
contains a large number of semiconductor storage cells, capable of storing a bit of information.
The word length of a computer is between 16-64 bits.
o
It is also known as the volatile form of memory, means when the computer is shut down,
anything contained in RAM is lost.
o
Cache memory is also a kind of memory which is used to fetch the data very soon. They are
highly coupled with the processor.
o
The most common examples of primary memory are RAM and ROM.
o
Secondary memory is used when a large amount of data and programs have to be stored for a
long-term basis.
o
It is also known as the Non-volatile memory form of memory, means the data is stored
permanently irrespective of shut down.
o
The most common examples of secondary memory are magnetic disks, magnetic tapes, and
optical disks.
Arithmetic & logical unit
o
Most of all the arithmetic and logical operations of a computer are executed in the ALU
(Arithmetic and Logical Unit) of the processor. It performs arithmetic operations like addition,
subtraction, multiplication, division and also the logical operations like AND, OR, NOT
operations.
Control unit
o
The control unit is a component of a computer's central processing unit that coordinates the
operation of the processor. It tells the computer's memory, arithmetic/logic unit and input and
output devices how to respond to a program's instructions.
o
The control unit is also known as the nerve center of a computer system.
o
Let's us consider an example of addition of two operands by the instruction given as Add LOCA,
RO. This instruction adds the memory location LOCA to the operand in the register RO and
places the sum in the register RO. This instruction internally performs several steps.
Output Unit
o
The primary function of the output unit is to send the processed results to the user. Output
devices display information in a way that the user can understand.
o
Output devices are pieces of equipment that are used to generate information or any other
response processed by the computer. These devices display information that has been held or
generated within a computer.
o
The most common example of an output device is a monitor
“Computers are divided into different types based on different criteria”
So, on the basis of size, there are five types of computers:
1.
2.
3.
4.
5.
And on the
Supercomputer
Mainframe computer
Minicomputer
Workstation
PC (Personal Computer)
basis of data handling capabilities, there are three types of computer:
1.
2.
3.
Now let us
Analogue Computer
Digital Computer
Hybrid Computer
discuss each type of computer in detail:
1. Supercomputer:
When we talk about speed, then the first name that comes to mind when thinking of computers is
supercomputers. They are the biggest and fastest computers(in terms of speed of processing data).
Supercomputers are designed such that they can process a huge amount of data, like processing
trillions of instructions or data just in a second. This is because of the thousands of interconnected
processors in supercomputers. It is basically used in scientific and engineering applications such as
weather forecasting, scientific simulations, and nuclear energy research. It was first developed by
Roger Cray in 1976.
Characteristics of supercomputers:
 Supercomputers are the computers which are the fastest and they are also very
expensive.
 It can calculate up to ten trillion individual calculations per second, this is also the
reason which makes it even more faster.
 It is used in the stock market or big organizations for managing the online currency
world such as bitcoin etc.
 It is used in scientific research areas for analyzing data obtained from exploring the
solar system, satellites, etc.
2. Mainframe computer:
Mainframe computers are designed in such a way that it can support hundreds or thousands of
users at the same time. It also supports multiple programs simultaneously. So, they can execute
different processes simultaneously. All these features make the mainframe computer ideal for big
organizations like banking, telecom sectors, etc., which process a high volume of data in general.
Characteristics of mainframe computers:
 It is also an expensive or costly computer.
 It has high storage capacity and great performance.
 It can process a huge amount of data (like data involved in the banking sector) very
quickly.
 It runs smoothly for a long time and has a long life.
3. Minicomputer:
Minicomputer is a medium size multiprocessing computer. In this type of computer, there are two or
more processors, and it supports 4 to 200 users at one time. Minicomputers are used in places like
institutes or departments for different work like billing, accounting, inventory management etc. It is
smaller than a mainframe computer but larger in comparison to the microcomputer.
Characteristics of minicomputer:
 Its weight is low.
 Because of its low weight, it is easy to carry anywhere.
 less expensive than a mainframe computer.
 It is fast.
4. Workstation:
Workstation is designed for technical or scientific applications. It consists of a fast microprocessor,
with a large amount of RAM and high speed graphic adapter. It is a single-user computer. It
generally used to perform a specific task with great accuracy.
Characteristics of Workstation:
 It is expensive or high in cost.
 They are exclusively made for complex work purposes.
 It provides large storage capacity, with better graphics, and a more powerful CPU when
compared to a PC.
 It is also used to handle animation, data analysis, CAD, audio and video creation, and
editing.
5. PC (Personal Computer):
It is also known as a microcomputer. It is basically a general-purpose computer and designed for
individual use. It consists of a microprocessor as a central processing unit(CPU), memory, input
unit, and output unit. This kind of computer is suitable for personal work such as making an
assignment, watching a movie, or at office for office work, etc. For example, Laptops and desktop
computers.
Characteristics of PC (Personal Computer):
 In this limited number of software can be used.
 It is smallest in size.
 It is designed for personal use.
 It is easy to use.
6. Analogue Computer:
It is particularly designed to process analogue data. Continuous data that changes continuously
and cannot have discrete values is called analogue data. So, an analogue computer is used where
we don’t need exact values or need approximate values such as speed, temperature, pressure etc.
It can directly accept the data from the measuring device without first converting it into numbers and
codes. It measures the continuous changes in physical quantity. It gives output as a reading on a
dial or scale. For example speedometer, mercury thermometer, etc.
7. Digital Computer:
Digital computers are designed in such a way that it can easily perform calculations and logical
operations at high speed. It takes raw data as an input and processes it with programs stored in its
memory to produce the final output. It only understands the binary input 0 and 1, so the raw input
data is converted to 0 and 1 by the computer and then it is processed by the computer to produce
the result or final output. All modern computers, like laptops, desktops including smartphones are
digital computers.
8. Hybrid Computer:
As the name suggests hybrid, which means made by combining two different things. Similarly, the
hybrid computer is a combination of both analog and digital computers. Hybrid computers are fast
like an analog computer and have memory, and accuracy like a digital computer. So, it has the
ability to process both continuous and discrete data. For working when it accepts analog signals as
input then it converts them into digital form before processing the input data. So, it is widely used in
specialized applications where both analog and digital data is required to be processed. A
processor which is used in petrol pumps that converts the measurem ents of fuel flow into quantity
and price is an example of a hybrid computer.