computer hardware and software jinchang wang. hardware vs. software hardware is something tangible....
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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)
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.
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
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.