TOPIC 2 ICT class notes for computer .pptx

TOPIC 2
COMPUTER SYSTEM
COMPONENTS

COMPUTER HARDWARE
• Hardware is the physical component of a computer system, the
electrical parts and devices that make up a computer
• They are categorized according to five basic operation they performs;
i. Input devices- we use to send data to computer processor/memory
ii. Processors- fetch, decode and execute data into information
iii. Memory – holds data/instructions that CPU needs
iv. Output devices – display information/results
v. Secondary storage devices – store data/information for later use

SYSTEM UNIT
• It is a boxlike case that houses the computer’s main hardware components
• Inside the system unit there’s:
Motherboard-large circuit board with thousands of electrical circuits
Power supply – provides electric power of all parts of the system unit
through main board
Cooling fan – keeps the system unit cool
Internal speaker – used for beeps when error is encountered
Drive bays- housing for the computer’s hard drive, floppy drive and CD-
ROM/DVD-ROM drives

MOTHERBOARD
Microprocessor (CPU) – central processing unit interprets and caries
out instructions given by the software
Memory- enables the computer to retain information
Chipset – a collection of chips that provide the switching circuitry
needed to move data
Input/output buses – pathways that allow the microprocessor to
communicate with input and output devices

MICROPROCESSOR (CPU)
The central processing unit, is the brain of the computer system
Administrative section of computer
Supervises the operations of the other units
CPU is connected to all other parts of the computer
Receives data and instructions given by user, processes accordingly and produces the output
This section not only executes the instruction but also controls all the permanent or
temporary storage of data, I/O activities as well as the function of different devices attached
with it
Its further dived into two
1. Control unit (CU)
2. 2. Arithmetic logic unit (ALU)

FOUR BASIC OPERATIONS OF CPU
• FETCH – the control unit takes the instruction that is stored in the
main memory
• DECODE – the control unit translates the instructions into machine
language or binary code
• EXECUTE – carryout the command
• STORE- write the result to memory

What are the types of memory
Are of two types, namely;
1. Volatile memory – (Random Access Memory/RAM; Cache Memory,
virtual memory) – contents of memory are erased when power
supply is turned off. Also called temporary storage
2. Nonvolatile memory-(Read Only Memory/ROM; Flash memory)-
contents of memory are NOT erased when power is turned off. Also
called permanent storage

Cache memory vs virtual memory
• Cache memory – located within the CPU chip, it is the memory the
microprocessor uses to store frequently used instructions and data
Faster than RAM
• Virtual memory – part of the hard disk is reserved as RAM
When RAM modules become full the CPU accesses the hard disk to
store and retrieve data
Slower than RAM

Starting and restarting a computer
• It is of two types of booting;
i. Cold booting
ii. Warm booting
Cold booting – when the computer is started after having been
switched off.
Warm booting – when the operating system alone is restarted (without
being switched off) after a system crash or freeze

Boot process
• There are two boot processes
Boot priority
Boot failure
1. Boot priority – the boot priority is the order in which these devices
are search to find a valid bootable operating system
2. Boot failure – boot failure means when you lose hard drive of your
computer

The input and output devices
1. INPUT DEVICES
• They are the devices that allow data to be input into the computer system. They include;
• Keyboard
• Mouse
• Touchpad
• Joystick
• Scanner
• Touchscreen
• Digital Camera
• Microphone, Graphics Tablet, Barcode Reader, Magnetic Stripe Card, Sensors etc

1. KEYBOARD
• The ideal input devices that is used to input texts, numbers and
instructions e.g CTRL+V into the computer
• Most keyboard have qwerty layout. Examples of keyboards include
rollup keyboard, laser or infrared, ergonomic, gaming keyboard etc
• Keyboards have two connection types;
a. USB type of connection
b. Serial type of connection

Parts of a keyboard
1. Special keys
• These keys work in combination with other keys. Some of the special keys
include; Alt, Caps lock, shift, ctrl, window key etc
2. Alphabetic keys
• These are marked with the English alphabets from A to Z . There are 26
alphabetic keys
3. Numeric keys
• The keys marked with numbers from 0 to 9 are called number keys.
• They are also placed at the right side of the keyboard known as numeric
keypad

4. Cursor movement keys
• Used to move the cursor in four direction up, down, left, right. They
are also called arrow keys
• Both tab key, space bar and arrow keys are used to move the cursor
5. Function keys
• The function keys are placed at the top row of the keyboard marked
with F1 to F12 used to perform special functions

Other keys include;
• Tab key – allows cursor to jump five spaces forward
• Delete key- erase anything typed from the right side of the cursor
• Enter key – tell the computer that you have finished a word or line and
brings the cursor down to the next line
• Shift key – used to type letters in capital or small case without using caps
lock key, also used to type symbols printed on the top of the number keys
• Backspace key – delete characters to the left of the cursor
• Caps lock key – type in capital letters
• Space bar – creates space between words

2. THE MOUSE
• A mouse is an external computer hardware device
• It allows a user to control the motion of a computer cursor
• It has the following parts
Mouse wire
Right button
Left button
Scroll wheel

Types of mouse
1. Optical mouse – uses light emitting diode, an optical sensor, and a
digital signal processing
2. Wireless mouse – mouse without wire or cord
3. GSTICK mouse – its pencil like mouse
4. Trackball mouse – consists of a ball held by a socket containing
sensors to detect a rotation of the ball

FUNCTIONS OF MOUSE
i. Move mouse cursor
ii. Open or execute program
iii. Drag and drop
iv. Scrolling
MOUSE SKILLS
v. Single clicking – it can be either left click or right click
vi. Dragging – moving a folder/file by pressing and holding left button
vii. Right click – clicking on the right side of the mouse
viii. Scrolling – either using the mouse scroll wheel

3. SCANNERS
• Device that optically scans images, printed text, handwriting or an
object
• Converts it to a digital image
• Types of scanners include; flatbed scanner, slide scanner, handheld
scanner
• Scanners scan a document as an image (this means you cannot edit it)
• Scan a document directly to a pdf file

4. THE JOYSTICK
• It is an input device that has a stick the pivots on a base and reports
its angle or direction to the device it is controlling such as an aircraft
or video game
• It also has multiple buttons that can also communicate with the
machine, such as the “a” button or “b” button that video games use
for jumping, crouching, etc

5. THE DIGITAL CAMERA
• A digital camera is an input device used to take video or still
photographs, or both, digitally by recording images by an electronic
image sensor

OUTPUT DEVICES
• Output devices are hardware devices that display or present
information to the user or other people
• Output devices lets a computer to communicate with you
• The devices which are used to display the data to the user either in
the form of hard copy or soft copy are called output devices

Examples of output devices
1. Display devices
2. Printer
3. Speaker
4. Headphone

1. DISPLAY DEVICES
• They include
• Monitor
• cathode ray tube (CRT)
• LCD technology,
• TFT (thin film transistor),
• LCD (Liquid Crystal Display) i.e Flat-panel display and gas plasma

1. MONITORS
• The monitors are display devices. Display is the most-used output device
on a computer
• Display provides instant feedback by showing you text and graphic images
as you work or play
Common definitions
Pixel- a pixel is a dot of color, the smallest part of a display
Resolution- number of pixels on display area. It is expressed like height x
weight
Aspect ration – ratio between number of horizontal pixel and the number
of vertical pixels

• Color depth – number of bit that are used to describe a color. There are three
components RGB i.e. red/green/blue
DISPLAY TECHNOLOGIES
• There are many technologies available such as;
Cathode ray tube (CRT)
Liquid crystal display (LCD)
Plasma
Project
NB: Only CRT and LCD are used in computer monitors (Plasma is used only in
large screen size >40 inches)

2. PRINTERS
• An output device that produces text and graphics on a physical
medium such as paper or transparency film
• Hard copy printout
• Either print using landscape or portrait
• Print requirement varies
• Types of printers include; non-impact printer, ink jet printer, laser
printer, thermal printer, plotters and large format printers, photo
printer etc

Whenever you want to buy printer consider
Budget
Printer speed
Color/black and white
Cost of printing per page
Print size of paper
Whether a network printer or not

3. Speaker
• Most Computers are fitted internal speakers although some may
require external speakers
• Speakers helps producing beeping sound or any other sound from the
computer

4. Projectors
• Is a device that takes the text and images displaying on a computer or
mobile
• Projects the images on a larger screen so that an audience can see the
image clearly

Factors affecting hardware selection
Define system capabilities
Specify magnitude of the problem- how big the problem is
Assess the competence the in house staff
Develop time frame for the selection process
Hardware and software to be considered as a package

COMPUTER HARDWARE SELECTION CRITERIA
1. Hardware must support current software as well as software planned for
procurement over the next planning
2. Hardware must be compatible with existing or planned networks
3. Hardware must be upgradeable and expandable to meet the needs of the next
planning interval
4. Hardware warranties must be of an appropriate length
5. Hardware maintenance must be performed by [local/remote vendor, in-house
personnel]
6. Whenever feasible, hardware standards will dictate procurement of like brands
and configurations to simplify installation and support
7. Routine assessments of installed infrastructure will feed an upgrade/replace
decision process

COMPUTER SOFTWARE
• Software is a set of computer programs, procedures and associated
documents describing the program and how they are to be used
• Types of soft wares
1. System software
2. Application software

System software
• System software includes the operating system and all the utilities that enable
the computer to function
• System software actually controls the hardware so that application software
can perform any action or task
• Types of system software include;
operating system
Utilities
Device drivers
Language translators
Compilers

Application software
• Application software include programs that do real work for user
• Examples include; payroll systems, inventory control, manage student
database, word processor, spreadsheet, database management
system etc
• Categories of application software;
Business software
Graphic and multimedia
Home/personal/education
Communication

Types of application software
• Presentation software
• Spreadsheet software
• Database software
• Multimedia software
• Word processing software etc
• Games

SOFTWARE SELECTION CRITERIA
1. Software must be compatible with current and future hardware over the
next planning interval
2. Software maintenance and warranties must be of appropriate length and
cost
3. Software help desk must be maintained by [vendor, third party, in-house
personnel]
4. Software must be standardized throughout the business to improve
purchasing power, simplify training, and facilitate support
5. Software must comply with current standards set by technology leadership
6. Software must support and enhance business goals

Functions of various computer software
1. Allocating system resources:
The system resources are time, memory, input, and output. The time in
the CPU is divided into time slices. The time slices is measured in terms
of milliseconds. Based on the priority of tasks the time slices are
assigned
2. Monitoring system activities:
The system security and system performance is monitored by system
software. System performance includes response time and CPU
utilization.

3. File and disk management:
The user needs to save, copy, delete, move and rename the files. The
system software will handle those functions. Disk and file management
is the technical task.
4. Managing Information
5. Manipulating Data
6. Constructing Visuals
7. Coordinating Resources
8. Calculating Figures

Storage devices
• They include
Hard disk
Floppy disks-
CD ROMs
DVDs
Pen drives
Blue ray disks

TOPIC 2 ICT class notes for computer .pptx

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TOPIC 2 ICT class notes for computer .pptx