Computer Hardware and Software

Jinchang Wang

Hardware vs. Software

• Hardware is something tangible.

• Computer hardware includes electronic circuitry and mechanisms.

• Software is instructions.

• Computer software is instructions to computer.

Electronic Computer

• In an electronic computer, main computing operations are accomplished on electronic switches at speed of electricity.

Binary Numbers

• A binary number is composed of 0’s and 1’s.

• Binary numbers and decimal numbers are two ways of recording numbers.

Only 0-1’s inside a Computer

• Everything (program, data, music, picture) in computer is coded in binary numbers that are composed of two digits, 0 and 1.

• Two distinctive, and reliable, states of an electronic circuit are off and on, corresponding to 0 and 1.

Bit and Byte• One binary digit is called a bit.

– For example, binary number 1011 has four bits.

• 1 byte = 8 bits.

• A character (a, A, b, B, ..., $, *, ...) is represented by a byte.– 01100001 for 1– 01011001 for Y– 00110010 for 2– 00111011 for ;

Storage Capacity Measures

• 1 Kbyte = 1 kilobyte 1,000 bytes

• 1 Mbyte = 1 megabyte 1,000,000 bytes

• 1 Gbyte = 1 gigabyte 1,000,000,000 bytes

• 1 Mbyte can store a novel with 500 pages (pure text)

Components of a Computer

Input devicesCPUInternal memorySecondary storageOutput devices

Input Devices

• To enter instructions and data into computers.

• Keyboard

• Mouse, trackball, joystick, …

• Pen-based input devices

• Scanners

• Voice input devices

• …

CPU

• Central Process Unit

• CPU is composes of:– Control Unit:

• Interprets programs (decoding)

• Directs and controls operations

– Arithmetic and Logic Unit• Performs computations.

• Performs logical comparisons.

Microprocessor

• CPU on a chip

• A chip is a self-contained integrated circuit

Internal Memory

• Made up of electronic circuits.

• Data and instructions are stored in it before they are processed in CPU.

RAM and ROM

• RAM– For users to store programs and data– Volatile

• ROM– For storing instructions for startup and

common instructions– Non-volatile

Secondary Storage

• Permanent storage – non-volatile

• Huge storage capacity

• Much slower than internal memory

• Hard disc, flash drive, optical disk, …

Hard Disk (1)

• Fixed magnetic disk– 1 to 5.25 inches– 20 GB to 200 GB– Contains 12 disk platters stacked on a spindle– Disk spins over a read/write head

Hard Disk (2)

Output Devices

• Monitors– CRT, LCD

• Printers– Laser printers, Ink-jet printers

Computer Software

• Computer software refers to instructions to computer.

• A computer program is a set of instructions for some purpose.

An Example of a Program- You enter a name, computer tells his/her address

Print “Enter a name” on screen;

Let X=(name-entered);

flag=0;

i=1;

Do repeatedly until flag=1:

if name-stored(i) = X,

then

print name-stored(i) and address-stored(i),

flag = 1;

otherwise

i=i+1;

Stop.

Types of Software

• System software – to control the hardware and basic operations of a computer– Operating system

• Utility software – for basic operations but not covered by operating systems.

• Application software – for particular applications.

Operating System

• Control internal memory, input/output devices, and secondary memories.

• Support other software

• Every computer has an operating system