Computer Hardware and Software

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Computer Hardware and Software

• Jinchang Wang

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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.

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Electronic Computer

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

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Binary Numbers

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

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Only 0-1s 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.

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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

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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)

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Components of a Computer

• Input devices
• CPU
• Internal memory
• Secondary storage
• Output devices

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Input Devices

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

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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.

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Microprocessor

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

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Internal Memory

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

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RAM and ROM

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

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Secondary Storage

• Permanent storage non-volatile
• Huge storage capacity
• Much slower than internal memory
• Hard disc, flash drive, optical disk,

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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

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Hard Disk (2)
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Output Devices

• Monitors
• CRT, LCD
• Printers
• Laser printers, Ink-jet printers

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Computer Software

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

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

• Print Enter a name on screen
• Let X(name-entered)
• flag0
• i1
• Do repeatedly until flag1
• if name-stored(i) X,
• then
• print name-stored(i) and address-stored(i),
• flag 1
• otherwise
• ii1
• Stop.

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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.

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Operating System

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