Computer Hardware Basics

Computer   

                       An electronic device operating under the control of instructions stored in its own memory that can accept, manipulate, and store data

Hardware components include:

1. Central processing unit (CPU)
2. Primary storage
3. Secondary storage
4. Input device
5. Output device
6. Communication device

Computer hardware functions

Input

• Keyboards, mouse, optical scanners
• Convert data into electronic form

Processing

• Central Processing Unit (CPU)
• Arithmetic-logic unit performs the arithmetic functions
• Control unit

Output

• Video display units, printers, etc.
• Convert electronic information into human-intelligible form

Storage

• Primary Storage Unit or memory
• Secondary Storage
• Magnetic disks and Optical disks

Control

• Control unit of the CPU
• Controls the other components of the computer

Computer System Components

Central Processing Unit

Central processing unit (CPU) (or microprocessor) -

the actual hardware that interprets and executes the program (software) instructions and coordinates how all the other hardware devices work together

Control unit - 

Interprets software instructions and literally tells the other hardware devices what to do, based on the software instructions

Arithmetic-logic unit (ALU) - 

Performs all arithmetic operations (for example, addition and subtraction) and all logic operations (such as sorting and comparing numbers)

Primary Storage

 The computer’s main memory, which consists of the random access memory (RAM), cache memory, and the read-only memory (ROM) that is directly accessible to the CPU

Random access memory (RAM) - the computer’s primary working memory, in which program instructions and data are stored so that they can be accessed directly by the CPU via the processor’s high-speed external data bus

Volatility : do not retain its contents when the power is switched off 

Save work frequently

Cache memory

                           Small unit of ultra-fast memory 

Used to store recently accessed or frequently accessed data > CPU does not have to retrieve this data from slower memory such as RAM.

Read Only Memory (ROM)

• The portion of a computer’s primary storage that does not lose its contents when one switches off the power > Permanent storage
• Can be read but cannot be overwritten
• Store start-up program : frequently used programs burnt into chips during manufacturing (Called firmware)

Peripherals

Peripheral is generic name for all input, output, and secondary storage devices that are part of the computer system but are not part of the system unit (i.e. CPU & primary storage)

Input Devices

equipment used to capture information and commands

Manual input devices -

Joystick

Keyboard

Microphone

Automated input devices -

Bar code scanner

Digital camera

Magnetic ink character reader

Output  Devices

• Video displays
• Cathode ray tube (CRT) like a television
• Most desktop PC screens
• Liquid crystal displays (LCD's)
• Laptop and PDAs, some PCs
• Printed Output
• Inkjet printer
• Spray ink on page
• Laser printer
• Electrostatic process like photocopying machine
• Voice response systems

Secondary Storage Devices

Magnetic Disks

Floppy disks

Magnetic disk inside a plastic jacket

Hard disk drives

Magnetic disk, access arms, and read/write heads in sealed module

RAID (Redundant arrays of independent disks)

Disk arrays of interconnected hard disk drives

Fault tolerant with multiple copies on several disks

•  Main memory provides only small amount of storage area for data, instruction, information.
•  Computer needs store larger amount of data,  instruction and information, more permanently than primary memory Q Secondary storage devices 

Computer Storage Fundamentals

Binary representation

   - Data are processed and stored in computer system through the presence or absence of signals

   - Either ON or OFF

ON = number 1

OFF = number 0

Bit and Byte

Bit (short for binary digit)

    - Smallest element of data

    - Either zero or one

Byte

    - Group of eight bits which operate as a single unit

    - Represents one character or number

Communication Devices

     - equipment used to send information and receive it from one 

         location to another

     Dial-up access

     Cable

     Digital subscriber line

     Wireless

     Satellite