Computer systems

Hardware and Software

Main Hardware Component Categories:

1. Central Processing Unit (CPU)

2. Main Memory

3. Secondary Memory / Storage

4. Input Devices

5. Output Devices

Central Processing Unit (CPU)

Comprised of​:

1. Control Unit:

   Retrieves and decodes program instructions

   Coordinates activities of all other parts of computer

2. Arithmetic & Logic Unit

   Hardware optimized for high-speed numeric calculation

   Hardware designed for true/false, yes/no decisions

Main Memory

Usually store in Ranfom Access Memory (RAM)

Composed of ones and zeros

Organized as follows:

bits: smallest piece of memory.

Has values 0 (off, false) or 1(on, true)

byte: 8 consecutive bits.

Address - Each byte in memory is identified by a unique number known as an address (starting at zero).

Memory Layout

• Code

• Static Data

• Heap / Free Store

• Stack

Stack and heap

grow toward each other.

Secondary Storage

• Non-volatile: data retained when program is not running or computer is turned off

• Comes in a variety of media:

  • magenetic: floppy disk, hard drive

  • Solid state drives

  • optical: CD-Rom, DVD

  • Flash drives, connected to the USB port

Input Devices

• Devices that send information to the computer from outside

• Many devices can provide input:

  • Keyboard, mouse, scanner, digital camera, microphone

  • Disk files

Software-Programs That Runon a Computer

• Categories of software:

  • System software: programs that manage the computer hardware and the programs that run on them

    • Examples: operating systems, utility programs, software development tools

  • Application software: programs that provide services to the user.

    • Examples: word processing, games, programs to solve specific problems