Chapter 7 Type of Source Statements
Machine Language Instruction Statements and Directive Statements 121
7.3 Machine Language Instruction Statements and Directive Statements

Machine language instruction statements

Machine language instructions are instructions that the microprocessor directly executes on its own
hardware. Each machine language code has a corresponding mnemonic.
Machine language instruction statements are statements that code these mnemonics. The assembler
will convert them into machine language code (called object code). After the program has been
converted to ROM, these statements will be executed by the microprocessor.
The instructions have the following features.
• Memory-oriented instruction set (all calculations performed throughout memory)
• Single and double-operand instructions
• Minimized instruction set and instruction codes
• Six addressing formats
The example below shows machine language instruction statements.

Directive statements

Directive statements are not converted to machine language code. Within programs they specify assem-
bler attributes to modify program structure and addresses, select radices, define constants, and control
list file style.
The example below shows directive statements.
mov 0xff, D0
mov data1, A0
mov D0, (A0)
add 1, D0
rts
global save
CONST equ 0x12
_TEXT section CODE, PUBLIC, 1
org 100
MESG dc ‘S’
end