The use of register organization make the instruction shorter and faster hence the execution time will be reduced significantly. The use of register used by the processor globally classify into two types such as:-
- General-purpose Register
2. Control and Status Register
1. General Purpose Register:-
It is accessed by the user which is accessed by the processor.
The register is said to be a user-visible register if these are used by the user or programmer during program development.
Register Organization Diagram
These registers are accessed by the user to hold any value and the values can be changed from time to time during the execution.
These are 3 types such as:-
- Address Register
- Data Register
- Condition code Register
It is defined as the user-visible registers, which always holds the address of memory or I/O process.
Hence the register always hold on negative value or positive value.
The user-visible register is said to be data register if it always stores or holds, source operates or results.
It is capable of storing or holding both positive and negative values.
Condition code register:-
The user-visible register, which stores the status flags of the processor are expensively thing is called a condition code register.
2. Control status Register:-
Other flags will set or reset every time during the execution of user program control and status.
The register is addressed by the processor only and used to execute the user program and known as control and status register.
The control and status register are of 4 types:-
- PC (program counter):- It is defined as the system register which holds the address of the next instruction to be executed after the execution of current instruction is completed.
- IR (Instruction Register):- It is defined as the register which holds the current instruction fetch and read from the memory.
Whenever the processor reads instructions from memory it will be brought through the database and will keep in IR from execution.
- MAR (memory address Register):- The register is said to be MAR if it holds the address of memory locations to be accessed by the processor.
The value of the PC is copied into MAR and the address will be sent to the memory through the address bus.
- MBR (memory buffer register):- The control and status register, which holds the data read from memory or data to be written into memory known as MBR or MDR.
The register may hold either operand values or instruction.
The register is directly connected to the database for sending or receiving data through the data bus