E I T – Unit – I Notes 2019- 20
B.Com (IT) - I Year I Semester
Unit – I
Introduction to Computers: Definition, Characteristics & Limitations of Computers,
Functional Block Diagram of Digital Computer, Functions Of Control Unit and ALU in CPU
Concepts Of Primary and Secondary Memory, Input / Output Devices.
Networks: Definition-Network Types-LAN, MAN,WAN. Network Topologies-Mesh, Bus,
Star, Ring, Hybrid
___________________________________________________________________________
Introduction to Computers:
Meaning of a Computer:
Computer is a machine that can solve problems by accepting data performing certain
operations and presenting the results of those operations under the direction of detailed step-
by-step instructions. Such a set of sequenced instructions, which cause a computer to perform
particular operations, is called a program. The term computer has been derived from the
word “COMPUTE” which means calculate.
Definition of a computer
Computer is an electronic device, used for performing calculations and controlling operations
that be either expressed in logical or numerical terms.
➢ It stores and process data in binary form according to instructions given to it in a
variable program.
➢ Computer need to be told exactly what to do and how to do to accomplish a task
➢ It is a combination of hardware and software
➢ Software is the set of instructions given to the computer to perform a task
➢ The physical parts that make up computer are called hardware, which are made of
circuits and transistors
The three main operations of computer are
1) Takes in data and instructions (input)
2) works with the data (processing)
3) puts out information (output)
Characteristics of a Computer:
The following are the main characteristics of a computer-
1. Speed: Computer is able to process the data and give the output in fractions of
seconds such that required information is available to the user on time and hence
enables him to take right decisions at the right time.
2. Accuracy: Computer is error free. There is no scope for inaccuracy in the results
given by the computer. Incorrect calculations, errors, mistake do not take place in a
computer system. If there errors they are due to the errors in the instructions given by
1 C.Swathi, Assistant Professor, Department of Computer Science, SJC
, E I T – Unit – I Notes 2019- 20
the programmer, inaccurate data, inconsistent data or defective programs as well as
defective system designs. Since the computer is capable of doing only what it is
instructed to do, fault instructions for data processing may lead to faulty results this is
known as GIGO (Garbage In Garbage Out)
3. Reliable: Today, computer is extensively used because of their reliability. The output
generated by the computer is very reliable to the extent that the input is reliable.
4. Storage capacity: Another important characteristic of a computer is that it has brain
of its own with brilliant memory. It can accept and store any information for a long
time. It stores large amount of data and can recall information instantly.The main
memory of the computer is relatively small and holds certain amount of information.
Therefore the data is stored in secondary memory
5. Versatile: The computer performs three basic operations. It accepts information from
the user; secondly it performs the basic arithmetic operations and logical operations
and finally generates the desired output in the desired form.
6. Automatic (Programmable): Computer is a device, which is more than a calculator.
Once instructions are given to the system it works automatically without any human
intervention until the completion of program until it meets logical instruction to
terminate the job.
7. Diligent: A computer is a device, which is indefatigable (untiring) and therefore does
not feel tired nor gets distracted like a human being. All the instructions are
performed at same speed and accuracy
8. Recreation: In recent years, computers were used mainly for entertainment and
amusement, like computer games and other programs, computer animation gives life
and movement to inanimate objects. Multimedia too helped in popularizing the use of
computers.
9. Networking capacity: A computer can be connected with other computers. This
feature of connectivity with other computers leads to the evolution of computer
networking.
10. Compactness: Now-a-day’s size of computers has decreased o lot due to increased
technology. The laptop and Notebook computers can be taken outside.
Limitations of A Computer:
Like any modern technology computers is also not free from limitations-
➢ Computer is a machine and therefore it is only a device that needs human skill to
operate.
➢ It does not work on its own and needs set of instructions to be given.
➢ It does not have natural intelligence and hence has to be instructed about every
step in detail.
➢ It is not a decision maker and has to be programmed to take an action if some
conditions prevail.
➢ Finally it does not learn by experience unlike intelligent human beings.
2 C.Swathi, Assistant Professor, Department of Computer Science, SJC
, E I T – Unit – I Notes 2019- 20
Elements of a Computer:
A computer consists of three basic elements/components such as hardware, software and
memory.
Hardware:
✓ The physical devices that make up a computer are referred to as hardware.
✓ It includes the tangible aspects of computers and can be touched such as mouse, printers,
monitor, microphone, scanner etc.
✓ Hardware is usually used for input and output purposes. It takes instructions from the user
from input devices such as mouse, key board etc and displays the output (after
processing) on the other hardware devices such as monitor, LCDs, scanner, printers etc.
Software:
✓ The software of the computer includes operating system which executes all the programs
and instructions given by the user.
✓ The computer software itself is categorized into two
SOFTWARE
SYSTEM SOFTWARE APPLICATION SOFTWARE
1. System Software
➢ It is collection of programs designed to operate, control, and extend the processing
capabilities of the computer itself. System software are generally prepared by
computer manufactures. These software products comprise of programs written in
low-level languages which interact with the hardware at a very basic level. System
software serves as the interface between hardware and the end users.
➢ Includes the software execution by the computer itself such as Windows and
DOS.
2. Application Software
➢ Application software products are designed to satisfy a particular need of a
particular environment.
➢ Application software may consist of a single program, such as a Microsoft's
notepad for writing and editing simple text. It may also consist of a collection of
programs, often called a software package, which work together to accomplish a
task, such as a spreadsheet package.
3 C.Swathi, Assistant Professor, Department of Computer Science, SJC
, E I T – Unit – I Notes 2019- 20
Memory:
➢ The memory of the computer can also be categorized under hardware but
sometimes it is considered as a separate element of the computer system.
➢ Memory allows the user to store the data and processes performed by the
computer.
➢ Memory is divided mainly into RAM, ROM and secondary storage devices.
➢ All these components are essential for the effective functioning of computer
system Central Processing Unit (CPU).
FUNCTIONAL BLOCK DIAGRAM OF COMPUTER:
• A Computer, like a human brain, receives data and instruction, stores them and
processes the data according to the instructions given to it.
• It receives data from input devices, stores them in memory and displays them through
on an output device
Central Processing Unit (CPU)
CPU is the component of computer system with the circuitry to control interpretation and
execution of instructions. It performs the process in parts of Input-Process-Output cycle. The
components of CPU are mounted (Fixed) on the main circuit board, called the
“motherboard”.
The various components of a Central Processing Unit are:
1. Arithmetic Logic Unit (ALU).
2. Control Unit.
Arithmetic and Logic Unit (ALU)
➢ It is that part of CPU where actual data processing occurs.
4 C.Swathi, Assistant Professor, Department of Computer Science, SJC
B.Com (IT) - I Year I Semester
Unit – I
Introduction to Computers: Definition, Characteristics & Limitations of Computers,
Functional Block Diagram of Digital Computer, Functions Of Control Unit and ALU in CPU
Concepts Of Primary and Secondary Memory, Input / Output Devices.
Networks: Definition-Network Types-LAN, MAN,WAN. Network Topologies-Mesh, Bus,
Star, Ring, Hybrid
___________________________________________________________________________
Introduction to Computers:
Meaning of a Computer:
Computer is a machine that can solve problems by accepting data performing certain
operations and presenting the results of those operations under the direction of detailed step-
by-step instructions. Such a set of sequenced instructions, which cause a computer to perform
particular operations, is called a program. The term computer has been derived from the
word “COMPUTE” which means calculate.
Definition of a computer
Computer is an electronic device, used for performing calculations and controlling operations
that be either expressed in logical or numerical terms.
➢ It stores and process data in binary form according to instructions given to it in a
variable program.
➢ Computer need to be told exactly what to do and how to do to accomplish a task
➢ It is a combination of hardware and software
➢ Software is the set of instructions given to the computer to perform a task
➢ The physical parts that make up computer are called hardware, which are made of
circuits and transistors
The three main operations of computer are
1) Takes in data and instructions (input)
2) works with the data (processing)
3) puts out information (output)
Characteristics of a Computer:
The following are the main characteristics of a computer-
1. Speed: Computer is able to process the data and give the output in fractions of
seconds such that required information is available to the user on time and hence
enables him to take right decisions at the right time.
2. Accuracy: Computer is error free. There is no scope for inaccuracy in the results
given by the computer. Incorrect calculations, errors, mistake do not take place in a
computer system. If there errors they are due to the errors in the instructions given by
1 C.Swathi, Assistant Professor, Department of Computer Science, SJC
, E I T – Unit – I Notes 2019- 20
the programmer, inaccurate data, inconsistent data or defective programs as well as
defective system designs. Since the computer is capable of doing only what it is
instructed to do, fault instructions for data processing may lead to faulty results this is
known as GIGO (Garbage In Garbage Out)
3. Reliable: Today, computer is extensively used because of their reliability. The output
generated by the computer is very reliable to the extent that the input is reliable.
4. Storage capacity: Another important characteristic of a computer is that it has brain
of its own with brilliant memory. It can accept and store any information for a long
time. It stores large amount of data and can recall information instantly.The main
memory of the computer is relatively small and holds certain amount of information.
Therefore the data is stored in secondary memory
5. Versatile: The computer performs three basic operations. It accepts information from
the user; secondly it performs the basic arithmetic operations and logical operations
and finally generates the desired output in the desired form.
6. Automatic (Programmable): Computer is a device, which is more than a calculator.
Once instructions are given to the system it works automatically without any human
intervention until the completion of program until it meets logical instruction to
terminate the job.
7. Diligent: A computer is a device, which is indefatigable (untiring) and therefore does
not feel tired nor gets distracted like a human being. All the instructions are
performed at same speed and accuracy
8. Recreation: In recent years, computers were used mainly for entertainment and
amusement, like computer games and other programs, computer animation gives life
and movement to inanimate objects. Multimedia too helped in popularizing the use of
computers.
9. Networking capacity: A computer can be connected with other computers. This
feature of connectivity with other computers leads to the evolution of computer
networking.
10. Compactness: Now-a-day’s size of computers has decreased o lot due to increased
technology. The laptop and Notebook computers can be taken outside.
Limitations of A Computer:
Like any modern technology computers is also not free from limitations-
➢ Computer is a machine and therefore it is only a device that needs human skill to
operate.
➢ It does not work on its own and needs set of instructions to be given.
➢ It does not have natural intelligence and hence has to be instructed about every
step in detail.
➢ It is not a decision maker and has to be programmed to take an action if some
conditions prevail.
➢ Finally it does not learn by experience unlike intelligent human beings.
2 C.Swathi, Assistant Professor, Department of Computer Science, SJC
, E I T – Unit – I Notes 2019- 20
Elements of a Computer:
A computer consists of three basic elements/components such as hardware, software and
memory.
Hardware:
✓ The physical devices that make up a computer are referred to as hardware.
✓ It includes the tangible aspects of computers and can be touched such as mouse, printers,
monitor, microphone, scanner etc.
✓ Hardware is usually used for input and output purposes. It takes instructions from the user
from input devices such as mouse, key board etc and displays the output (after
processing) on the other hardware devices such as monitor, LCDs, scanner, printers etc.
Software:
✓ The software of the computer includes operating system which executes all the programs
and instructions given by the user.
✓ The computer software itself is categorized into two
SOFTWARE
SYSTEM SOFTWARE APPLICATION SOFTWARE
1. System Software
➢ It is collection of programs designed to operate, control, and extend the processing
capabilities of the computer itself. System software are generally prepared by
computer manufactures. These software products comprise of programs written in
low-level languages which interact with the hardware at a very basic level. System
software serves as the interface between hardware and the end users.
➢ Includes the software execution by the computer itself such as Windows and
DOS.
2. Application Software
➢ Application software products are designed to satisfy a particular need of a
particular environment.
➢ Application software may consist of a single program, such as a Microsoft's
notepad for writing and editing simple text. It may also consist of a collection of
programs, often called a software package, which work together to accomplish a
task, such as a spreadsheet package.
3 C.Swathi, Assistant Professor, Department of Computer Science, SJC
, E I T – Unit – I Notes 2019- 20
Memory:
➢ The memory of the computer can also be categorized under hardware but
sometimes it is considered as a separate element of the computer system.
➢ Memory allows the user to store the data and processes performed by the
computer.
➢ Memory is divided mainly into RAM, ROM and secondary storage devices.
➢ All these components are essential for the effective functioning of computer
system Central Processing Unit (CPU).
FUNCTIONAL BLOCK DIAGRAM OF COMPUTER:
• A Computer, like a human brain, receives data and instruction, stores them and
processes the data according to the instructions given to it.
• It receives data from input devices, stores them in memory and displays them through
on an output device
Central Processing Unit (CPU)
CPU is the component of computer system with the circuitry to control interpretation and
execution of instructions. It performs the process in parts of Input-Process-Output cycle. The
components of CPU are mounted (Fixed) on the main circuit board, called the
“motherboard”.
The various components of a Central Processing Unit are:
1. Arithmetic Logic Unit (ALU).
2. Control Unit.
Arithmetic and Logic Unit (ALU)
➢ It is that part of CPU where actual data processing occurs.
4 C.Swathi, Assistant Professor, Department of Computer Science, SJC
