Types of Assembly language statements

Assembly language programs consist of three types of statements:

Type 1 – Imperative Statements (Machine Instructions)

These are executable statements that directly correspond to machine instructions. They specify actions to be performed at runtime.

Format:

[Label]  <Mnemonic><Operand(s)>

Examples:

START:  MOV  A, B      ; Move contents of B into A

ADD  R1, R2    ; Add R1 and R2

JMP  LOOP      ; Unconditional jump to LOOP

BAL  14, SUBR  ; Branch and Link to SUBR

Sub-types:

• Memory Reference: Instructions that access memory (e.g., LOAD, STORE).
• Register Reference: Instructions operating on registers (e.g., ADD, SUB).
• I/O Instructions: Instructions for input/output operations.
• Branch Instructions: Conditional and unconditional jumps (JMP, BNE, BE).

Type 2 – Declarative Statements (Data Definition)

These define constants or reserve memory for data. They are processed at assembly time to allocate storage and initialize values.

Examples:

DATA1  DC  F'5'         ; Define constant: integer 5 (fullword)