Thursday, April 21, 2016

Description and Example of Operand Field

For an instruction, the operand field specifies the data that are to be acted on by the operation. An instruction may have zero, one, or two operands 

For Example :

NOP                               no operands : does nothing

INC AX                          the operand; adds 1 to the contents of AX

ADD WORD1, 2              two operands; adds 2 to the contents of memory word WORD1

In a two-operand instruction, the first operand is the destination operand. It is the register or memory location where the result is stored. The second operand is the source operand. The source is usually not modified by the instruction.

For an assembler directive, the operand field usually contains more information about the directive.