Computer Registers
A register is a very small amount of very fast memory that is built into the CPU (central processing unit) in order to speed up its operations by providing quick access to commonly used values. Registers refers to semiconductor devices whose contents can be accessed (i.e., read and written to) at extremely high speeds but which are held there only temporarily (i.e., while in use or only as long as the power supply remains on).
Registers are the top of the memory hierarchy and are the fastest way for the system to manipulate data.Registers are normally measured by the number of bits they can hold, for example, an 8-bit register means it can store 8 bits of data or a 32-bit register means it can store 32 bit of data.
Registers are used to store data temporarily during the execution of a program. Some of the registers are accessible to the user through instructions. Data and instructions must be put into the system. So we need registers for this.
The basic computer registers with their names, size and functions are listed below
Register Symbol |
Register Name |
Number of Bits |
Description |
AC |
Accumulator |
16 |
Processor Register |
DR |
Data Register |
16 |
Hold memory data |
TR |
Temporary Register |
16 |
Holds temporary Data |
IR |
Instruction Register |
16 |
Holds Instruction Code |
AR |
Address Register |
12 |
Holds memory address |
PC |
Program Counter |
12 |
Holds address of next instruction |
INPR |
Input Register |
8 |
Holds Input data |
OUTR |
Output Register |
8 |
Holds Output data |
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