Overview of Computer System

Class: SSS One

Definition of Computer System

• Computer system can be defined as an electronic device which manipulates data and produces output using step-by-step instructions.
• A programmable machine that receives, stores, retrieves, processes and outputs data
• A computer may be defined as 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.

Constituents of a Computer

The two major constituents of the computer are:
Hardware and software

Hardware

Hardware can be defined as all the parts of the computer that are tangible. I.e. they are the parts of the computer you can see, touch, or handle.
Examples of Hardware
The following list represents a basic set of hardware found in most computers
a. PC case
b. Motherboard
c. Hard Disk Drive (HDD)
d. Floppy Disk Drive (FDD)
e. Compact Disk Drive (CDD)
f. Digital Video Disk Drive (DVD)
g. Monitor
h. Keyboard
i. Power supply circuit
j. Mouse
k. Cables and wires.

Classification of Hardware

Hardware can be classified into:
1. Input unit: This unit helps the users to enter data and instructions into the computer. Examples; keyboard, lightpen, Joystick, mouse, etc.
2. Output Unit: The output unit communicates the results of data processing carried out by the computer to the user. Examples; Monitor, Projector, Printer, etc.
3. Memory Unit: The memory unit holds data and instructions for the computer. Examples; RAM, ROM, Flash drive, Hard disk, etc
4. Processing unit: The processing unit carries out or executes the instructions of a computer program. Example; CPU
Note
System Unit: System unit is that part of the computer that houses electronic components of the computer used to process data.
Peripherals: A computer peripheral is any external device that provides input and output for the computer. The term peripherals refer to all hardware devices that are attached to the computer and are controlled by the computer system. Peripheral devices are sometimes called "I/O devices"

Software

Software is defined as a set of instructions and procedures passed to the computer to perform certain activities or tasks.
It can also be defined as a set of instructions that direct the activities of the computer system to undertake a specific task. Unlike hardware, the software cannot be seen or touched.
Examples of Software
The following list represents some software found in most computers.
a. Windows
b. MS word
c. Norton anti-virus
d. CorelDraw
e. MS Access
f. MS Excel
g. BASIC programming Language
h. Assembler, etc

Types of Software

Computer software is divided into two broad groups, these are
1. System Software
2. Application software

System Software

System software is a collection of programs that supports computer operations.
It can also be defined as programs that help run the computer hardware and software.
Examples of System Software
Operating System,
Translators
Utility programs.

Application Software

These are software that allows humans (the users) to accomplish one or more specific (non-computer) tasks.
Examples of Application Software
Word processing software
Spreadsheet software
Presentation software
Database packages
Graphics packages
Gaming Software, Etc.

Characteristics of the Computer

The characteristics possessed by computers can be listed as follows
1. Speed: A computer can add and subtract numbers, compare letters to find alphabetic sequences, and move and copy numbers and letters in a fraction of time. The speed of a computer is measured in Hertz (Hz); Which is the number of tasks the computer can perform in one second. A 4 Giga Hertz (4 GHz) CPU can perform 4 billion tasks in one second. This feature is very important and useful for humans.
2. Accuracy: Computers are very accurate. They can perform hundreds of thousands of operations with great accuracy as there are no moving parts to wear and go wrong. They can run without error for months at a time.
3. Storage: Because various computer devices can store lots of data in a small area, there are tremendous savings in the storage area required to maintain the records necessary in a business.
4. Versatility: A computer can perform many different types of tasks. You can perform arithmetic operations, do word processing, send an email, and use the Internet.
5. Automation: Automation is one of the most important features of the computer. Once a command is given to the computer, it can perform the job without the need for human help until the job has been completed.
6. Diligence: Computers do not get tired like humans. They can perform the jobs continuously for days and even weeks together without errors and without affecting speed and accuracy.
7. Cost: Hardware costs have been decreasing at an estimated annual rate of 25 per cent.
8. Electronic in nature: The computer is made from electrical components like transistors, integrated circuits (ICs), Microprocessor, capacitors, resistors, and diodes, and hence, require electricity to function
9. Interactive: The computer consists of a user interface that allows users to enter data and instructions (commands) into the computer and also get feedback from it.

Limitations of a Computer

Computer is a very intelligent machine but it also suffers from many limitations such as:
1. The computer can’t do anything unless they are the first program to perform a specific task.
2. A computer cannot interpret the data they generate
3. Computers cannot detect if the operator feeds any data into it.
4. Computers cannot implement the decision that they suggest.
5. Prolong usage of the computer can lead to fatigue and sight problem
6. Over-dependence on the use of computers can stop or hold work whenever there is a breakdown by the system or a virus attack in the system
7. It can be hacked

Classification of Computer

Classification According to Purpose

a. General Purpose Computer
A general-purpose computer is designed to perform a wide variety of tasks
b. Specific Purpose Computer
These computers are designed to handle a single problem.

Classification According to Type of Data-handling Techniques

a. Analog Computers
These are computer that represents data by measurable quantities, such as voltages, and rotation of gears, to solve problems.
b. Digital Computer
A digital computer is a computer that performs calculations and logical operations with quantities represented as digits, usually in the binary number system.
c. Hybrid Computer A hybrid computer is a type of computer that offers the functionalities of both a digital and an analogue computer

Classification of Computer by Size/Speed

a. Microcomputer
Microcomputers are relatively small and low-cost. They consist of a CPU, an input unit, an output unit, a storage unit, and the software
b. Minicomputers
Minicomputers are digital computers, generally used in multi-user systems. They have high processing speed and high storage capacity than microcomputers. Minicomputers can support up to 4 – 200 users simultaneously
c. Mainframe Computers
Mainframe computers are multi-user, multi-programming, and high-performance computers. They operate at a very high speed, have a very large storage capacity, and can handle the workload of many users.
d. Supercomputer
Supercomputers are the fastest and most expensive machines. They have high processing speed compared to other computers. The speed of a supercomputer is generally measured in FLOPS (Floating Point Operations Per Second). Some of the faster supercomputers can perform trillions of calculations per second

Block Diagram of the Computer System