COMPUTER SYSTEMS
Introduction
Computer system has three components namely: Hardware, software and liveware (computer user).
A system is a collection of different entities that collectively work together to achieve a desired goal.
Examples of systems are human body, social system, school system etc.
A computer system is a collection of three components namely hardware, software and liveware
entities that work together to receive, process, manage and present information in a meaningful
format using computers.
Components of a Computer System
The computer system consists of three major parts namely
i). Hardware
These are the physical or tangible components of a computer system, which one can touch and
feel/see. They consist of the mechanical, electrical and electronic parts of the system e.g monitor,
system unit, keyboard and mouse
ii). Software
Is a set of instructions that direct a computer on what to do. They guide the computer in each and
every activity that happens inside the computer during data processing. The programs are also written
to help the computer users perform various tasks using the computer. The software is intangible,
flexible and changeable in nature.
They are mainly classified into two categories namely system software and application software.
iii). Liveware (computer user)
Refers to users who have computer knowledge and hence can properly utilize the computer hardware
and software as well as in participation in hardware and software selection.
Computer Hardware
The computer hardware is classified into four categories namely
input devices,
output devices
central processing unit,
storage devices.
Input devices
These are devices which accept data and send it to the CPU. The input devices have two tasks to
perform:
i). Read data from the medium from which it is stored
ii). Code it into a form that can be understood by the computer
Input devices are classified according to how they are used to enter data as follows:
1) Keying devices i.e. keyboard, keypad
2) Pointing devices i.e. mouse, joy stick, light pen, track ball.
3) Scanning and other data capture devices
4) Speech recognition or voice input devices
5) Touch screen, digitizer and digital cameras
Keying devices
Keying or typing is the most common way to input data. A keying device converts typed numbers,
letters and special characters into machine readable form before processing takes place.
Keyboard and keypad
They enter into a computer by typing (pressing its keys). A keypad is a tiny keyboard which is
mostly used on small portable computers, calculators, mobile phones etc.
Common types of keying devices include:
Traditional keyboard : It is a full sized rigid keyboard as discussed in Chapter 1 of the
Handout.
, Flexible / Rollup Keyboard: It is a more portable type of keyboard that can be folded and
packed into a bag. Rollup computer keyboards are
extremely good for traveling. Simply roll them up
and then unroll them when you need them again.
Typically the material is either silicone or
polyurethane. These devices are meant to be rolled
up, rather than folded, as folding can damage the
circuitry.
Ergonomic Computer Keyboards
Ergonomic computer keyboards is a computer keyboard designed with
ergonomic considerations to minimize muscle strain and a host of related
problems. An ergonomic keyboard is designed to make typing easier and lessen
the strain that your hands may suffer, such as "Carpal Tunnel Syndrome".
Keypad : is a miniature keyboard used on portable devices such as PDAs,
laptops, palm notes, calculators and mobile phones, etc. keypad is a
set of buttons arranged in a block or "pad" which usually bear digits,
symbols and usually a complete set of alphabetical letters.
If it mostly contains numbers then it can also be called a numeric
keypad. Keypads are found on many alphanumeric keyboards and on
other devices such as calculators, push-button telephones, combination
locks, and digital door locks, which require mainly numeric input.
A computer keyboard usually has a small numeric keypad on the side, in addition to the other
number keys on the top, but with a calculator-style arrangement of buttons that allow more
efficient entry of numerical data. This number pad (commonly abbreviated to "numpad") is
usually positioned on the right side of the keyboard because most people are right-handed.
Many laptop computers have special function keys which turn part of the alphabetical keyboard
into a numerical keypad as there is insufficient space to allow a separate keypad to be built into
the laptop's chassis. Separate external plug-in keypads can be purchased.
Braille keyboard: is an accessibility option for the blind. It consists of keys identified by raised
dots.
, Advantages of keyboard
- Its very reliable compared to other methods of text input (voice input)
- Is very cost effective, since every computer comes with a keyboard and there are no additional
costs .
Pointing devices
Enter data or instructions by controlling a pointer or cursor on the screen. Some examples pointing
devices include:- mouse, trackball, joystick, light pen, and stylus.
i). A mouse
Enter data or instructions by controlling a pointer on the screen. Generally there are three types of
mice available in the market today namely mechanical, optical and cordless.
Mechanical mouse
It has a ball underneath, two buttons and an optional scroll wheel located between the left and right
buttons.
The optical mouse
An optical mouse uses a light-emitting diode and photodiodes to detect movement relative to the
underlying surface, unlike wheeled mice which use a set of one
rolling ball and two chopper wheels for motion detection. It does
not have any moving parts.
Laser mouse
A laser mouse is a type of computer mousing device that uses a laser beam rather than a ball to
track the movement of the user's hand. Laser mice are becoming increasingly common because
they are perceived to have better tracking ability
Distinguish between mechanical mouse, optical mouse and laser mouse.
Optical mice make use of one or more light-emitting diodes (LEDs) and an imaging array of
photodiodes to detect movement relative to the underlying surface, rather than internal moving
, parts as does a mechanical mouse. A Laser mouse is an optical mouse that uses coherent (Laser)
light.
The difference between a regular optical mouse and a laser mouse is the light used to track
movement. A regular optical mouse uses an LED light in the optical engine, while a laser mouse
uses a laser to track movement. The more dots per inch (dpi) a mouse can track, the more
sensitive and accurate it is. A typical optical mouse tracks between 400dpi and 800dpi, while
laser mice track more than 2,000dpi.
Neither is really better; it all depends on your needs and preferences. Unless you're a gamer or a
graphic artist with a need for precise movement, you'll probably find a 2,000dpi laser mouse too
sensitive. Many gaming mice, however, allow you to switch sensitivity levels so that you have
precision when you need it but can revert to 400dpi or 800dpi for regular mousing.
Besides their tracking speeds, laser mice work on nearly every surface, whereas optical mice
may experience trouble tracking on black or shiny surfaces.
Cordless ( wireless) mouse
Cordless or wireless mouse is a battery powered mouse that uses radio or infrared waves instead of
being physically connected to the system unit.
Uses of a mouse
- To select options from menus or from a set of icons by clicking the mouse button.
- To position the cursor when editing text or using design package
- To select an object in a drawing or a piece of text to be copied, moved or deleted.
Advantages of using a mouse
- Is easy and convenient to use
- It is inexpensive
- Most modern software includes an option to use it
- It selects a position on screen much more quickly than a keyboard
Disadvantages
- Cannot be used to input text easily, you need a keyboard to do that.
- It is relatively slow for selecting menu options
- Requires a flat surface to operate
- It is not accurate for drawing purposes
ii). Track ball
A track ball is like a mouse that has been turned upside down. The ball is on top, and the user moves
the ball without moving the mouse. The track ball does not require a flat surface to operate.
ii). Joystick
Introduction
Computer system has three components namely: Hardware, software and liveware (computer user).
A system is a collection of different entities that collectively work together to achieve a desired goal.
Examples of systems are human body, social system, school system etc.
A computer system is a collection of three components namely hardware, software and liveware
entities that work together to receive, process, manage and present information in a meaningful
format using computers.
Components of a Computer System
The computer system consists of three major parts namely
i). Hardware
These are the physical or tangible components of a computer system, which one can touch and
feel/see. They consist of the mechanical, electrical and electronic parts of the system e.g monitor,
system unit, keyboard and mouse
ii). Software
Is a set of instructions that direct a computer on what to do. They guide the computer in each and
every activity that happens inside the computer during data processing. The programs are also written
to help the computer users perform various tasks using the computer. The software is intangible,
flexible and changeable in nature.
They are mainly classified into two categories namely system software and application software.
iii). Liveware (computer user)
Refers to users who have computer knowledge and hence can properly utilize the computer hardware
and software as well as in participation in hardware and software selection.
Computer Hardware
The computer hardware is classified into four categories namely
input devices,
output devices
central processing unit,
storage devices.
Input devices
These are devices which accept data and send it to the CPU. The input devices have two tasks to
perform:
i). Read data from the medium from which it is stored
ii). Code it into a form that can be understood by the computer
Input devices are classified according to how they are used to enter data as follows:
1) Keying devices i.e. keyboard, keypad
2) Pointing devices i.e. mouse, joy stick, light pen, track ball.
3) Scanning and other data capture devices
4) Speech recognition or voice input devices
5) Touch screen, digitizer and digital cameras
Keying devices
Keying or typing is the most common way to input data. A keying device converts typed numbers,
letters and special characters into machine readable form before processing takes place.
Keyboard and keypad
They enter into a computer by typing (pressing its keys). A keypad is a tiny keyboard which is
mostly used on small portable computers, calculators, mobile phones etc.
Common types of keying devices include:
Traditional keyboard : It is a full sized rigid keyboard as discussed in Chapter 1 of the
Handout.
, Flexible / Rollup Keyboard: It is a more portable type of keyboard that can be folded and
packed into a bag. Rollup computer keyboards are
extremely good for traveling. Simply roll them up
and then unroll them when you need them again.
Typically the material is either silicone or
polyurethane. These devices are meant to be rolled
up, rather than folded, as folding can damage the
circuitry.
Ergonomic Computer Keyboards
Ergonomic computer keyboards is a computer keyboard designed with
ergonomic considerations to minimize muscle strain and a host of related
problems. An ergonomic keyboard is designed to make typing easier and lessen
the strain that your hands may suffer, such as "Carpal Tunnel Syndrome".
Keypad : is a miniature keyboard used on portable devices such as PDAs,
laptops, palm notes, calculators and mobile phones, etc. keypad is a
set of buttons arranged in a block or "pad" which usually bear digits,
symbols and usually a complete set of alphabetical letters.
If it mostly contains numbers then it can also be called a numeric
keypad. Keypads are found on many alphanumeric keyboards and on
other devices such as calculators, push-button telephones, combination
locks, and digital door locks, which require mainly numeric input.
A computer keyboard usually has a small numeric keypad on the side, in addition to the other
number keys on the top, but with a calculator-style arrangement of buttons that allow more
efficient entry of numerical data. This number pad (commonly abbreviated to "numpad") is
usually positioned on the right side of the keyboard because most people are right-handed.
Many laptop computers have special function keys which turn part of the alphabetical keyboard
into a numerical keypad as there is insufficient space to allow a separate keypad to be built into
the laptop's chassis. Separate external plug-in keypads can be purchased.
Braille keyboard: is an accessibility option for the blind. It consists of keys identified by raised
dots.
, Advantages of keyboard
- Its very reliable compared to other methods of text input (voice input)
- Is very cost effective, since every computer comes with a keyboard and there are no additional
costs .
Pointing devices
Enter data or instructions by controlling a pointer or cursor on the screen. Some examples pointing
devices include:- mouse, trackball, joystick, light pen, and stylus.
i). A mouse
Enter data or instructions by controlling a pointer on the screen. Generally there are three types of
mice available in the market today namely mechanical, optical and cordless.
Mechanical mouse
It has a ball underneath, two buttons and an optional scroll wheel located between the left and right
buttons.
The optical mouse
An optical mouse uses a light-emitting diode and photodiodes to detect movement relative to the
underlying surface, unlike wheeled mice which use a set of one
rolling ball and two chopper wheels for motion detection. It does
not have any moving parts.
Laser mouse
A laser mouse is a type of computer mousing device that uses a laser beam rather than a ball to
track the movement of the user's hand. Laser mice are becoming increasingly common because
they are perceived to have better tracking ability
Distinguish between mechanical mouse, optical mouse and laser mouse.
Optical mice make use of one or more light-emitting diodes (LEDs) and an imaging array of
photodiodes to detect movement relative to the underlying surface, rather than internal moving
, parts as does a mechanical mouse. A Laser mouse is an optical mouse that uses coherent (Laser)
light.
The difference between a regular optical mouse and a laser mouse is the light used to track
movement. A regular optical mouse uses an LED light in the optical engine, while a laser mouse
uses a laser to track movement. The more dots per inch (dpi) a mouse can track, the more
sensitive and accurate it is. A typical optical mouse tracks between 400dpi and 800dpi, while
laser mice track more than 2,000dpi.
Neither is really better; it all depends on your needs and preferences. Unless you're a gamer or a
graphic artist with a need for precise movement, you'll probably find a 2,000dpi laser mouse too
sensitive. Many gaming mice, however, allow you to switch sensitivity levels so that you have
precision when you need it but can revert to 400dpi or 800dpi for regular mousing.
Besides their tracking speeds, laser mice work on nearly every surface, whereas optical mice
may experience trouble tracking on black or shiny surfaces.
Cordless ( wireless) mouse
Cordless or wireless mouse is a battery powered mouse that uses radio or infrared waves instead of
being physically connected to the system unit.
Uses of a mouse
- To select options from menus or from a set of icons by clicking the mouse button.
- To position the cursor when editing text or using design package
- To select an object in a drawing or a piece of text to be copied, moved or deleted.
Advantages of using a mouse
- Is easy and convenient to use
- It is inexpensive
- Most modern software includes an option to use it
- It selects a position on screen much more quickly than a keyboard
Disadvantages
- Cannot be used to input text easily, you need a keyboard to do that.
- It is relatively slow for selecting menu options
- Requires a flat surface to operate
- It is not accurate for drawing purposes
ii). Track ball
A track ball is like a mouse that has been turned upside down. The ball is on top, and the user moves
the ball without moving the mouse. The track ball does not require a flat surface to operate.
ii). Joystick
