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. – for 1 – for Y – for 2 – 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 devices CPU Internal memory Secondary storage Output 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