The mnemonic field identifies whether a statement is an instruction statement or a pseudo-op statement.
The mnemonic field identifies whether a statement is an instruction statement or a pseudo-op statement. Each mnemonic requires a certain number of operands in a certain format.
For an instruction statement, the mnemonic field contains an abbreviation like ai (Add Immediate) or sf (Subtract From). This mnemonic describes an operation where the system microprocessor processes a single machine instruction that is associated with a numerical operation code (op code). All instructions are 4 bytes long. When the assembler encounters an instruction, the assembler increments the location counter by the required number of bytes.
For a pseudo-op statement, the mnemonic represents an instruction to the assembler program itself. There is no associated op code, and the mnemonic does not describe an operation to the processor. Some pseudo-ops increment the location counter; others do not.