Internal Organization of Computer
Components:
- 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.
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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