The CPU registers are high-speed access storage areas that are within the processor. They are also known as computer registers. Registers are inbuilt within the processor to increase the speed of access. They are faster than cache and main memory. They are used to temporarily store data that is currently being executed on the CPU.
The main function of the CPU register is to store data and address the processes that are currently being executed in the computer processor. Register are classified into special-purpose or general-purpose. The most common types of computer registers are Program Counter (PC), Instruction Register (IR), Accumulator Register (AR), Memory Address Register (MAR), and Memory Buffer Register (MBR) among others discussed in this article.
Functions of CPU registers
Each register has its own defined functions but for most of them, these are some of the standard tasks that they perform.
- Registers store data temporarily for the process that is in execution. The data includes intermediate results, operands, or any other that is required for execution.
- Registers help the processor to increase its operation speed by availing the data at high speed. The high access speed of the register ensures that the processor can operate optimally without waiting to retrieve data from slower components like cache and RAM.
- Some registers like program counters are used to keep track of the flow of execution by determining which instruction to execute next and where it is in the memory. Hence registers help control the flow of program execution.
- Again computer registers are used to facilitate arithmetic and logic operations within the ALU of the processor. This increases the execution of these operations within the computer processor.
Types of computer registers and their functions
A standard computer processor is designed with a number of registers that are used for various functions. CPU registers can be classified depending on the data they store or their purpose. They include data and address registers and special-purpose or general-purpose registers. The most common CPU registers are.
The program Counter (PC)
The register stores the memory address of the next instruction to be executed by the processor. It is also known as the instruction address register. PC tells the CPU where the next instruction to be executed is to be fetched from the main memory.
Instruction Register (IR)
After the instruction has been fetched from the main memory it is stored in the instruction register. This is the instruction that is currently being executed by the processor.
Accumulator Register (AC)
It is located within ALU and it is used to store intermediate results of arithmetic and logic operations. A processor can have many AC registers, but the more they are the more complex the system design.
Memory Address Register (MAR)
It is used to hold the address of where the CPU wants to read or write data from or to the memory respectively. When a computer processor wants to read data from the main memory (RAM) address it will put that address on the MAR to be fetched.
Memory Buffer Register (MBR)
While the MAR holds the address where the CPU wants to read or write, the MBR holds the real data or instruction from the RAM or to the CPU. The buffer holds the instruction that has been fetched from the RAM. It also holds data from the CPU going to the RAM.
I/O Address Register
They are used to store the addresses of different input and output devices. When the CPU needs the address of a specific input or output device then it fetches it from these addresses.
I/O Buffer register
They temporarily store data that is being exchanged between different input and output devices and the processor.
Stack Pointer (SP)
It is a special-purpose register that is used to keep track of the memory stack. SP stores the address and data of the stack that is currently on top. It uses a stack pointer to store or point to the address of the topmost stack.
A flag in computing is like an alarm or an alert that indicate if something has happened or not. Flag registers are used to control the flow of process execution by indicating the status of the operation.
These registers are used to manage memory segmentation and how they are accessed. A segment register is used to store the starting address of each memory segment. This helps the CPU determine where a specific segment start.