Module Nine: Computer Hardware (Notes)
Computer hardware is the physical part of the computer that we can see and touch. The physical things that we see and touch are know as hardware. For a typical computer, the hardware consists of input devices, processing unit, storage devices output devices
Computer hardware is categorized into five main groups
a) Input devices
b) Central processing unit and memory
c) Output devices
d) Secondary storage devices
e) Communication devices
Computer input devices
They accept and convert data into electronic machine readable form for direct entry or through telecommunications links into a computer system for processing.
Example of input hardware
i. Light pen is a stylus with a light sensitive tip that is used to draw directly on a computer's video screen or to select information on the screen by pressing a clip in the light pen or by pressing the light pen against the surface of the screen. The pen contains light sensors that identify which portion of the screen it is passed over.
ii. Mouse is a pointing device designed to be gripped by one hand.
It has a detection device (usually a ball) on the bottom that enables the user to control the motion of an on screen pointer, or cursor, by moving the mouse on a flat surface. As the device moves across the surface, the cursor moves across the screen.
To select items or choose commands on the screen, the user presses a button on the mouse.
iii. Joystick is a pointing device composed of a lever that moves in multiple directions to navigate a cursor or other graphical object on a computer screen.
iv. Keyboard is a typewriter like device that allows the user to type in text and commands to the computer.
v. Optical Scanner uses light sensing equipment to convert images such as a picture or text into electronic signals that can be manipulated by a computer.
For example, a photograph can be scanned into a computer and then included in a text document created on that computer. The two most common scanner types are the flatbed scanner, which is similar to an office photocopier, and the handheld scanner, which is passed manually across the image to be processed.
vi. Microphone is a device for converting sound into signals that can then be stored, manipulated, and played back by the computer. Voice recognition is a device that converts spoken words into information that the computer can recognize and process.
Types of input hardware
1. Direct keyboard input devices
In this method data is entered directly by using keyboard
2. Non Keyboard input devices
This method use scanner, digital camera, sensor etc
Pointing devices
Allow end users to issue commands or make choices by moving a cursor on the display screen. Examples of pointing devices include: Electronic Mouse, Trackball, ,Point Stick
Processing Hardware
The components that process data are located on the computer motherboard.
A motherboard is a plastic board covered by several computer circuits.
The motherboard contain: the bus, CPU, system clock, memory socket, ports, keyboard controller and supporting chips. The most important chip on any computer motherboard is the processor (central processing unit).
Processor
This is the part of the computer that does all the thinking and processing activities
The central processing unit (CPU) is the main processing component of a computer system. It works in hand with other circuits known as main memory and registers to carry out processing Tasks
Processor Speed
Processors are often distinguished by their speed and people tend to have different expectations for speed. How you perceive the speed of your computer will also be impacted by the programs you choose to run.
Choosing a processor which can handle more processes will decrease the amount of time you wait. You are encouraged to consider the type of programs you want to run and how fast, this will inform what type of processor you want.
Every processor has a system clock (a pulsing quartz crystal).
The clock's speed (in cycles per second = Hz) determines how fast the microprocessor can process data and execute program instructions.
MHz = "mega-hertz" = million cycles per sec (e.g. 100 MHz, 700 MHz)
GHz = billions of cycles per sec (latest generation of AMD and Intel processors)
Parts of the Processor
The processor is often referred to as the CPU or central processing unit, which clearly identify this component’s role within the system and consists of electronic circuits that interpret and executes program instruction.
- Control unit (CU)
- Arithmetic logic unit (ALU)
The processor
Control unit:
Tell the ALU how to carry out a program instructions. Directs the movements of electronic signals between main memory and logic units.
Directs electronic signals between main memory and the input or output devices.
The Arithmetic Logic Unit (ALU)
Performs basic arithmetic & logic operations that the architecture (i.e. this particular type of processor) supports.
- Arithmetic operations: plus, minus, multiplication, division.
- Logical operations: comparisons such as =, <, >, <=, >=
- Bitwise logic operations (AND, NOT, OR, XOR)
Registers
- Contained in CPU in arithmetic logic unit.
- They are temporary memory that store data temporarily during processing
- Provides working area for computation
- Hold programs instructions and data from main memory into registers just before processing.
Components that supports CPU
- When managing data to operate the CPU requires other several components.
- Some of these components are motherboard, expansion slot, clock, battery, chip set, address bus.
Storage Hardware
Storage hardware provides storage of information and programs for retrieval by the computer.
Storage hardware are available are found in two main types
a) Primary Storage
The primary storage unit (main memory) holds data and instructions between processing steps and supplies them to the CU and ALU during processing.
All data and programs must be placed into main memory before they can be processed.
Memory also hold data temporarily after being processed by CPU but before release to output or storage device.
It is volatile, programs and data within it vanish when computer is turned off
Main Memory (RAM)
It is called RAM because from the fact that data can be stored and retrieved at random from anywhere in the electronic RAM Chip in a approximately equal amount of time, nor matter, what specific data locations are
- Capacity varies in different computers:
- Its size determines amount of data be processed
- RAM Capacities is expressed in Megabytes.
- It is available in 32, 64,128, 256, 512 megabytes.
- Larger capacities are also available in Gigabytes and Terabytes for very large computers
Main memory tasks
- Memory has three main tasks.
- Holds data for processing
- Holds the instructions (programs) for processing data.
- Holds processed data.
b) Secondary Storage
Secondary storage is one of the computer hardware that is used to store information.
The information could be programs, which tells the computer what to do, data to be processed or the results of computation
The function of Secondary storage is to provide a means of storing these software and data in a form that is relatively permanently or non-volatile data is not lost even when the computer is turned off .
Functions
- They store and backup data and programs
- Transport files and programs from one location or computer to another
Secondary Storage Types
Four most common types of secondary storage devices are:
Examples of Storage Hardware
1. Floppy Disks known also as Diskettes or floppies. They are inexpensive removable media. Are primarily used to save and transport documents.
Have larger capacity and are able to store and retrieve information much faster
It is available a internal hard disk, external hard disk
3. Optical Disk
Technology based on using a laser to read tiny spots on a plastic disk. The disks are currently capable of storing billions of characters of information.
Two common formats of optical disks are:
a) Compacts Disks (CDs)
Capacities from 650MB-1GB
CD-ROM read only: cannot be written on or erased by user
CD-R (Compact disk recordable) disks. Can be written to once, but can be read many times later on . Used to create custom music CDs and to archive data
CD-RW reusable . Used to create and edit larger multimedia presentations
b) DVDs - Digital Versatile Disks
DVDs have larger capacities than CDs
Capacities from 1GB - 4.5GB or more
DVD-ROM read only: cannot be written on or erased by user
Used to distribute theatre-quality video and sound
DVD-R can be written to once, expected to replace CD-R as price decline
DVD-RW reusable.
Computer storage elements
- Bit is the smallest element of data, (binary digit) which can have a value of zero or one.
The capacity of memory chips is usually expressed in terms of bits.
- Byte is the basic grouping of bits that the computer operates as a single unit.
It consists of 8 bits and is used to represent one character of data in most computer coding schemes (e.g. 8 bits = 1 byte) .
- 1 Kilobyte (Kb)=1,000 bytes (or to be exact 1024 bytes)
- Megabytes is a measurement of storage capacity. Abbreviated as MB or M= one million bytes (1,024 or 220)
- Gigabyte is a measurement of storage capacity. Abbreviated as GB or G= one billion bytes (1,024 or 230)
- Terabyte is a measurement of storage capacity. Abbreviated as TB or T= one trillion bytes ((1,024 or 240)
Output Hardware or Devices
Output hardware consists devices that translate processed data into a form that humans can understand.
Information is output in either hardcopy, softcopy and audio
Output devices include
- Audio Response Units such as speakers
- Printers convert Soft copy to hardcopy
- Video Display Units Monitors. Flat panel Display with LCD and CRTs Screen
Display
Displays commonly take one of two forms:
> Video screen with a cathode ray tube (CRT)
> Video screen with a liquid crystal display (LCD).
A CRT based screen, or monitor, looks similar to a television set.
Information from the CPU is displayed using a beam of electrons that scans a phosphorescent surface that emits light and creates images. Flat Panel or LCD -based screen displays visual information on a flatter and smaller screen than a CRT based video monitor. LCDs are frequently used in laptop computers.
Output devices printers
A printer an output device that prints characters, symbols and perhaps graphics on papers. Examples of impact printers are Dot matrix printers, Line printers, Ink jet printers. Laser Printers and Multifunction Printer.
Printers
Printers come in several shapes, sizes and colors.
The type of printer to be chosen depends on several factors such as
- Volume of the output
- Quality of the print required
- Location of the printer
- Requirements for color
- Requirements for multiple copies
Communication Hardware
Facilitate the connection between computers and between group of connected computers called network. Examples are modem, NIC,HUB Switch, bridge and routers.
Power Supply
- The Power Supply for a computer is very vital in more ways than simply providing electricity to the parts of a computer.
- The power supply has connections that allow it to deliver power to all the components that require it (there are many cords that deliver powers to different components).
- For high end computers, a quality power supply is needed to make sure that your expensive parts don’t get damage by surges or other electrical malfunctions.
- Computer parts are designed expecting certain electrical values.
- If these values aren’t met, the part won’t function properly and can even become damaged.
- Each component requires a certain type of connection which is why the power supply has so many different connections.
- UPS (Uninterruptible Power Supply)
- Gives time to shut down and It has a battery inside it and will allow time to shut down the computer correctly if there is a power cut.
- It also protects the computer when power is low (brown outs).
Battery is a device used to store power in laptop
Very little power usage is desired to maximize battery life
Surge Protector
- To protect against spikes in power
- If there is a power cut shut down the computer and switch the UPS off before the power comes back on to protect the computer equipment against surges as the power is restored.
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