A register is a written record or official list of names, dates, and other important information. It is used to document a variety of events, such as births and deaths. It can also be used to register something like a copy of an official document.
The register in a computer is an interface between the program and data storage, such as main memory and disk memory. The control units take instructions from the register and decode them. They then execute them by sending the required signals to the appropriate components. The result is displayed on the user screen.
Registers are located on the CPU (central processing unit) in memory, and they operate much faster than other forms of storage, including caches. The size of the registers, or the number of bits in a register, determines their speed.
There are different types of registers, each with a specific purpose. These include instruction registers, arithmetic and logic registers, and floating point registers.
General-purpose registers are usually 16-bit in width and store data of all sorts. They are also known as integrated registers because they contain both address and data.
Instruction registers are generally the largest of all registers. They are also the fastest, as they allow a processor to execute a single instruction in one step. They are also often used to keep track of the current state of a process, such as which instruction is active and how long it has been in operation.
Special-purpose registers are not as wide, but they are more complex and capable of storing large amounts of data. These include the program counter and the register that stores an address that identifies the next address to be accessed after an instruction is completed.
In older processors, a register must be set before the processor can use it. This is to ensure that the register is used only for the specific purpose it was intended, and not repurposed for a different purpose.
This is because a register can be modified, or renamed, by a computer system. This can affect the way programs are executed by a CPU.
A register is also a fast, low-latency storage location for a processor. The latency of access to registers is very fast compared to memory operations, even when a CPU’s cache is in use.
Another type of register is called a memory address register or MAR. This register directly drives the address bus and memory address decoder.
During an instruction’s execution, the MAR is loaded with a memory address that the CPU needs to access in RAM or ROM. This address is often a part of the instruction, and it must be loaded when an arithmetic or logic operation requires a memory word to be retrieved.
The registers in a computer are stored in RAM, ROM, or both. They are not part of the main memory, but they act as a fast and inexpensive form of memory for the processor. They are also often used to store small amounts of data.