Computer Hardware; Input-Output Devices and Both input-output devices
Computer Hardware
Hardware is a comprehensive term for all of the physical parts of a computer, as distinguished from the data it contains or operates on, and the software that provides instructions for the hardware to accomplish tasks. The boundary between hardware and software is slightly blurry - firmware is software that is "built-in" to the hardware, but such firmware is usually the province of computer programmers and computer engineers in any case and not an issue that computer users need to concern themselves with.
We can divided Hardware into two kinds:
1. Internal Hardware (Components) (System Unit)
2. External Hardware (Peripherals) (Input Devices
Output Devices)
The CPU has 2 components .
1. CU (Control Unit):
Directs different parts of the computer to carry out instructions. It controls communication and coordination between input/output devices.
1. Control Unit’s main function in CPU to process data.
2. The Control Unit extracts instructions from memory and decodes and executes them.
3. Manages all resources of a computer
4. Manages a 4-stepbasic operation which is called a machine cycle or processing cycle.
Machine Cycle
• 4 step in Machine Cycle :
• Step 1: Fetch – retrieve an instruction from memory
• Step 2: Decode – translate instruction in a form
ALU can understand (command)
• Step 3: Execute – Carry out instruction
• Step 4: Store – copy results to Memory
2. ALU (Arithmetic Logic Unit):
Performs all arithmetical calculations such as addition and multiplication & makes all logical decisions.
• An arithmetic logic unit (ALU) is one of the core components of all central processing units.
• Arithmetic operations: e.g., add, subtract, multiply, divide, square root, cosine, etc.
• Logical operations: e.g., compare two numbers to see which is greater, check whether a true/false statement is true, etc.
• Comparison operation: e.g: AND, OR, NOT, NAND, NOR, XOR etc.
(MU): Memory Unit/ Register set:
1. Memory locations are needed for storing pointers, counters, return addresses, temporary results, and partial products during multiplication.
2. As memory access is time consuming process better to have those values in processor registers.
3. To have a large number of registers, it have to connect with a common bus system.
It will be part of various micro-operation like arithmetic, logic and shift operation in the processor.
Input devices:
Mouse: Commonly Used in personal computer and workstations.
Track ball: Commonly used in laptop (notebook) computer.
Joystick: Commonly used in video games, flight simulators, training simulators and for controlling industrial robots.
Electronic pen: Used to directly point with it on the screen to select menu items or icons or directly draw graphics on the screen.
Touch screen: Enables users to choose from available options by simply touching with their finger the desired icon or menu item displayed on the screen.
Microphone: Microphone is an input device to input sound that is then stored in a digital form.
Optical Mark reader: (OMR) Scanner capable of recognizing a pre specified type of mark by pencil or pen.
Bar code Reader: Scanner used for reading (decoding) bar coded datat.
MICR: MICR is used by banking industry for faster processing of large volume of cheques.
Digitizer: Input device used for converting (digitizing) pictures maps and drawings into digital form for storage in computer.
Output devices:
Monitor: Monitor are the most popular output devices used for producing soft-copy output.
Printer: Most common output devices for producing hard-copy output.
Plotters: Plotters are an ideal output device for architectures engineers, city planners and other who need to foutinely generate high precision, hard copy graphic output of widely varying sizes.
Projector: An output device that can be directly plugged to a computer system for projecting information form a computer on to a large screen.