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computer architecture

Module by: Anh Duong

Summary: computer architecture

Computer Hardware

A computer may be divided into six logical units.
Input Unit
  • Obtain information from input devices: keyboards and mouse devices.
  • Place the information at the disposal of the other units to be processed.
Output Unit
  • Take information that has been processed.
  • Place it on output devices: displayed on screens, printed on paper.
Memory Unit
  • RAM (random access memory) is volatile, stores program and data.
  • ROM (read only memory) is non-volatile, contains fundamental instructions.
Arithmetic and Logic Unit (ALU)
  • Perform all the arithmetic and logic operations: addition, subtraction, comparison, etc..
CPU
  • Tell the input unit when information should be read into the memory unit.
  • Tell the ALU when information from the memory should be used in calculations.
  • Tell the output unit when to send information from the memory unit to certain output devices.
Secondary Storage.
  • Permanent storage areas for programs and data: magnetic tapes, magnetic hard disks, floppy disk, CD ROM

Computer Software

  • A computer program: set of instructions used to operate a computer to produce a specific result.
  • Computer programming: writing computer programs.
  • Programming languages: languages used to create computer programs.
Machine Languages
Example: 0101010 000000000001 000000000010
  • The lowest level of computer languages.
  • Programs consist of entirely of 1s and 0s.
  • Programs can control directly to the computer’s hardware.
  • Machine language instructions consist of two parts:
    • Instruction part (opcode) is the leftmost group of bits and tells the computer the operation to be performed.
    • Address part specifies the memory address of the data to be used in the instruction.
Assembly Languages
Example:
LOAD BASEPAY
ADD OVERPAY
STORE GROSSPAY
  • Perform the same tasks as machine languages, but use symbolic names for opcodes and operands.
  • An assembly language program must be translated into a machine language program.
Translation program (assembler)Machine languageprogramAssembly languageprogram
  • Machine languages and assembly languages are called low-level languages since they are closest to computer hardware.
High-level Programming Languages
  • Create computer programs using instructions that much easier to understand: English-like included with mathematical notations.
  • Programs written in high-level languages must be translated into a low level language using a program called a compiler.
  • Each line in a high-level language program is called a statement.
Ex: Result = (First + Second)*Third.
Application and System Software
  • Application software: perform particular tasks required by the users.
  • System software: must be available to any computer system to operate. The most important system software is the operating system (MS-DOS, UNIX, MS WINDOWS, MS WINDOWS NT)
  • Multitasking systems: operating systems allow user to run multiple programs. graphics1.png

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