INTRODUCTION
A computer is a programmable machine that receives input, stores and automatically
manipulates data, and provides output in a useful format. The first electronic computers were
developed in the mid-20th century (1940–1945). Originally, they were the size of a large room,
consuming as much power as several hundred modern personal computers (PCs). Technically, a
computer is a programmable machine. This means it can execute a programmed list of
instructions and respond to new instructions that it is given. Classification of computers:
Computers are classified according to their data processing speed, amount of data that they can
hold and price. Depending upon their speed and memory size, computers are classified into
following four main groups.
1. Supercomputer.
2. Mainframe computer.
3. Minicomputer.
4. Microcomputer.
1. Supercomputer
Supercomputer is the most powerful and fastest, and also very expensive. It was developed in
1980s. It can process trillions of instructions in seconds. Governments specially use this type of
computer for their different calculations and heavy jobs. Different industries also use this huge
computer for designing their products.
2. Mainframe Computers
Mainframe computers are also large-scale computers but supercomputers are larger than
mainframe. These are also very expensive. The mainframe computer specially requires a very
large clean room with air-conditioner. This makes it very expensive to buy and operate.
3.Minicomputers
These are smaller in size, have lower processing speed and also have lower cost than mainframe.
These computers are known as minicomputers because of their small size as compared to other
computers at that time. The capabilities of a minicomputer are between mainframe and personal
computer. These computers are also known as midrange computers.
4.Microcomputer
The microcomputers are also known as personal computers or simply PCs. Microprocessor is
used in this type of computer. These are very small in size and cost. The IBM‘s first
microcomputer was designed in 1981 and was named as IBM-PC. After this many computer
hardware companies copied the design of IBM-PC. The term ―PC-compatible‖ refers any
personal computer based on the original IBM personal computer design.
Computer memory:
Computer memory refers to the physical devices used to store data or programs (sequences of
instructions) on a temporary or permanent basis for use in an electronic digital computer.
Types of memory:
1) Primary memory
2) Secondary memory
1) Primary memory: It is directly accessible by the CPU. The primary memory is of two types
such as
a) ROM memory
b) Read /Write memory
2) Secondary memory: The maximum capacity of primary memory is limited. So to handle more
data than allowed by primary memory, secondary memory is used. And it is non-volatile i.e. data
is not lost due to current failure. Magnetic tape, Floppy disk and Hard disk are some examples of
secondary memory.
Software:
A set of instructions (in machine code) given to the computer to solve user problems and to
control different operations of the computer is known as computer software. The software is
developed in programming languages. The Computer software is classified into two main
categories:
1. Application software.
2. System software.
1. Application Software
A set of programs used to solve particular problems of user through computer is called
Application software. It is also known as application package. Some of application packages are:
2. System Software
System software is a set of programs that control the operations of a computer and devices
attached with the computer. It creates links between user and computer as well as controls the
execution of application programs. The examples of system software are:
A computer is a programmable machine that receives input, stores and automatically
manipulates data, and provides output in a useful format. The first electronic computers were
developed in the mid-20th century (1940–1945). Originally, they were the size of a large room,
consuming as much power as several hundred modern personal computers (PCs). Technically, a
computer is a programmable machine. This means it can execute a programmed list of
instructions and respond to new instructions that it is given. Classification of computers:
Computers are classified according to their data processing speed, amount of data that they can
hold and price. Depending upon their speed and memory size, computers are classified into
following four main groups.
1. Supercomputer.
2. Mainframe computer.
3. Minicomputer.
4. Microcomputer.
1. Supercomputer
Supercomputer is the most powerful and fastest, and also very expensive. It was developed in
1980s. It can process trillions of instructions in seconds. Governments specially use this type of
computer for their different calculations and heavy jobs. Different industries also use this huge
computer for designing their products.
2. Mainframe Computers
Mainframe computers are also large-scale computers but supercomputers are larger than
mainframe. These are also very expensive. The mainframe computer specially requires a very
large clean room with air-conditioner. This makes it very expensive to buy and operate.
3.Minicomputers
These are smaller in size, have lower processing speed and also have lower cost than mainframe.
These computers are known as minicomputers because of their small size as compared to other
computers at that time. The capabilities of a minicomputer are between mainframe and personal
computer. These computers are also known as midrange computers.
4.Microcomputer
The microcomputers are also known as personal computers or simply PCs. Microprocessor is
used in this type of computer. These are very small in size and cost. The IBM‘s first
microcomputer was designed in 1981 and was named as IBM-PC. After this many computer
hardware companies copied the design of IBM-PC. The term ―PC-compatible‖ refers any
personal computer based on the original IBM personal computer design.
Computer memory:
Computer memory refers to the physical devices used to store data or programs (sequences of
instructions) on a temporary or permanent basis for use in an electronic digital computer.
Types of memory:
1) Primary memory
2) Secondary memory
1) Primary memory: It is directly accessible by the CPU. The primary memory is of two types
such as
a) ROM memory
b) Read /Write memory
2) Secondary memory: The maximum capacity of primary memory is limited. So to handle more
data than allowed by primary memory, secondary memory is used. And it is non-volatile i.e. data
is not lost due to current failure. Magnetic tape, Floppy disk and Hard disk are some examples of
secondary memory.
Software:
A set of instructions (in machine code) given to the computer to solve user problems and to
control different operations of the computer is known as computer software. The software is
developed in programming languages. The Computer software is classified into two main
categories:
1. Application software.
2. System software.
1. Application Software
A set of programs used to solve particular problems of user through computer is called
Application software. It is also known as application package. Some of application packages are:
- Word processing software.
- Spreadsheet software.
- Database Management System software.
- Graphics software.
- Communication software.
System software is a set of programs that control the operations of a computer and devices
attached with the computer. It creates links between user and computer as well as controls the
execution of application programs. The examples of system software are:
- Operating systems.
- Utility programs.
- Device Drivers.
- Language Processors.
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