Address Bus
- Signals related to address between processor and the memory.
- It is Unidirectional
Data Bus
- Sends data between processor and memory unit and input/output devices.
- It is bi-directional.
Control bus
- Carries Signals relating to the control and coordination of all activities within the computer.
- It is Unidirectional.
Address is a location where data is stored in Computer memory.
Memory Unit
- It is made up of a number of partitions.
- Each partition consists of an Address and its Contents.
- MAR- Memory Address Register.
- MDR- Memory data Register.
- ALU- Arithmetic and logic Unit.
- PC- Program Counter.
- CIR- Current instruction register
- Read data first written into MAR (Memory address Register).
- Read signal is sent to Computer memory using Control bus.
- Contents are put in MDR (memory data Register).
Processor
Processor consists of Arithmetic and Logic Unit ALU (eg. add, subtract etc..) and Logic (eg: AND, OR, NOT etc..)
Control Unit
- The control unit controls the operation of the memory , Processor and input / Output devices.
- It contains the CURRENT INSTRUCTION REGISTER (CIR) and the program counter (PC).
- The CIR contains current instruction during processing and PC contains the address of the next instruction to be executed.
INPUT and OUTPUT devices
- Input-entering the data (eg. keyboards, touch screens and microphones).
- Output- Retrieving the data (eg. printers, monitors and loud speakers).
The fetch-execute Cycle
Here there is some data we need to decode the data and execute it.
Fetch
The next instruction is fetched from the memory address currently stored in the program counter (PC) and is then stored in the Current Instruction Register (CIR).
Execute
The processor passes the decoded information as control signals to appropriate components within the Computer Systems.