Computer Hardware and Software

1. Computer Hardware and Software Jinchang Wang

2. Hardware vs. Software • Hardware is something tangible. • Computer hardware includes electronic circuitry and mechanisms. • Software is instructions. • Computer software is instructions to computer.

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

4. Binary Numbers • A binary number is composed of 0’s and 1’s. • Binary numbers and decimal numbers are two ways of recording numbers.

5. 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.

6. 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 ;

7. 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)

8. Components of a Computer Input devices CPU Internal memory Secondary storage Output devices

9. Input Devices • To enter instructions and data into computers. • Keyboard • Mouse, trackball, joystick, … • Pen-based input devices • Scanners • Voice input devices • …

10. 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.

11. Microprocessor • CPU on a chip • A chip is a self-contained integrated circuit

12. Internal Memory • Made up of electronic circuits. • Data and instructions are stored in it before they are processed in CPU.

13. RAM and ROM • RAM • For users to store programs and data • Volatile • ROM • For storing instructions for startup and common instructions • Non-volatile

14. Secondary Storage • Permanent storage – non-volatile • Huge storage capacity • Much slower than internal memory • Hard disc, flash drive, optical disk, …

15. 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

16. Hard Disk (2)

17. Output Devices • Monitors • CRT, LCD • Printers • Laser printers, Ink-jet printers

18. Computer Software • Computer software refers to instructions to computer. • A computer program is a set of instructions for some purpose.

19. 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.

20. 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.

21. Operating System • Control internal memory, input/output devices, and secondary memories. • Support other software • Every computer has an operating system