# What are Arithmetic Micro-operations?

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The operations implemented on data stored in registers are known as micro-operations. A micro-operation is a basic operation implemented on the data saved in one or more registers.

There are various micro-operations including addition, subtraction, increment, and decrement.

It is described by the following statement −

R3 → R1 + R2

The following statement instructs the information or contents of register R1 to be inserted to data or content of register R2 and the sum must be converted to register R3.

## Subtract Micro-Operation

Example −

R3 → R1 + R2' + 1

Subtract micro-operation are using minus operator we create 1's complement and add 1 to the register which obtains subtracted, i.e R1 - R2 is similar to R3 → R1 + R2' + 1

## Increment/Decrement Micro-Operation

In Increment and decrement micro-operations, it is usually implemented by adding and subtracting 1 to and from the register respectively.

R1 → R1 + 1

R1 → R1 – 1

The following table demonstrates the symbolic representation of several Arithmetic Micro-operations.

Symbolic RepresentationDescription
R3 ← R1 + R2The contents of R1 plus R2 are moved to R3.
R3 ←R1$R1 - R2The contents of R1 minus R2 are moved to R3. R2 ←R1$ R2'Complement the contents of R2 (1's complement).
R2 ←R1$R2' + 12's complement the contents of R2 (negate). R3 ← R1 + R2' + 1R1 plus the 2's complement of R2 (subtraction). R1 ←R1$ R1 + 1It can increment the contents of R1 by one.
R1 ←R1\$ R1 - 1It can decrement the contents of R1 by one.

The increment and decrement micro-operations are symbolized by plus one and minus-one operations, respectively. These micro-operations are performed with a combinational circuit or with a binary up-down counter.

The arithmetic operations of multiply and divide are not shown in the table. These two operations are valid arithmetic operations but are not contained in the essential set of micro-operations.

In this case, the signals that implement these operations propagate by gates, and the result of the operation can be transferred into a destination register through a clock pulse immediately after the output signal propagates by the combinational circuit.

The multiplication operation is performed with a series of add and shift micro-operations. The division is executed with a series of subtracting and shift micro-operations.