Friday, February 19, 2016

Computer Internals

Internal Organization of Computer

Computer Internals - Parts

  • Computer can be broken on to three parts: CPU (Central Processing Unit), Memory and I/O (Input/Output) devices.
  • Memory is to store (temporary or permanent) information.
  • CPU is to process information stored in memory.
  • I/O device is to provide a means of communicating with CPU.
  • CPU is connected to memory and I/O through strips of wire called a bus.
  • Bus inside a computer carries information from one place to another.
  • There are three types of buses: address bus, data bus, and control bus.
  • For a device to be recognized by CPU, it must be assigned a unique address.
  • Address bus is used to identify the devices and memory connected to the CPU.
  • Data bus is used to carry information in and out of a CPU.
  • Control bus is to provide read or write signals to device.
  • Address bus is a unidirectional bus, which means that the CPU uses the address bus only to send out addresses.
  • The total number of memory locations addressable by a CPU is always equal to 2x where x is the number of address lines or bits.
  • Data bus is a bidirectional bus. CPU must use them to send or receive data.
  • The more lines or bits in a data bus, the better the CPU.
  • Processing power of a computer is related to the size of its busses.
  • RAM and ROM are referred as Primary Memory.
  • Storage device such as a disk is called Secondary Memory.
  • ROM is to provide information that is fixed and permanent.
  • RAM is to store information that is not permanent and can change with time.
  • Programs such as operating system and application packages are loaded in to RAM and processed by the CPU.
  • Program stored in memory provides information to the CPU to perform an action.
  • Function of CPU is to fetch the instructions from memory, decode and execute them.
  • CPU is equipped with ALU (Arithmetic Unit), Fetching Unit, Decoding Unit, Control Unit and Registers to perform fetch, decode and execution operations.
  • CPU uses register for temporary storage while executing instructions.
  • Program counter (PC or IP (Instruction Pointer)), a register, is to point address of the next instruction to be executed by CPU.
  • Fetching unit in CPU fetches the instructions from the address, pointed by PC, in memory.
  • Decoding unit in CPU interprets the instruction fetched in to CPU and tells what steps the CPU should take.
  • ALU is to perform add, subtract, multiply, divide and Boolean operations.
  • Control unit is to control the operations of other units.

Computer Internals - Organization

Related topics:
Microcomputer System   |   Microcomputer System Architecture   |   Numbering System   |   Memory Basics   |   Digital Logic   |   ASCII Code   |   ROM and RAM Memory

List of topics: Microcomputer

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