- 2.3.10. -
Table of Contents
2. TMT Pascal Language Description
2.3. Built-in Assembler
2.3.10. Operand Expressions
2.3.10. Operand Expressions
Operand expressions are built from operands and operators.
Operands are constants, registers, labels, and memory locations.
Operators combine operands and alter their attributes.
Each instruction allows only certain combinations of operands.
Operand expressions can be classified into three classes:
- Immediate operands or constants.
- Registers.
- Memory and label operands.
Immediate operands
PUSH 10
MOV AX, 10
MOV AX, offset Start
Here 10, and Start are immediate operands.
The values of AX and 10 can be determined immediately;
the value of offset Start is determined during linking.
Registers
TMT Pascal built-in assembler allows use of any 8, 16, or 32-bit
80386 registers.
XOR AH, AL
LSL EAX,EAX
MOV AX, FX
Memory and label operands
Memory operands refer to the data stored in memory locations.
Usually, one uses the square brackets [..] or the type ptr
operator to ensure that the argument is treated as a memory location.
Label operands refer to locations in code.
MOV EBX,[0]
POP Word Ptr [88]
POP Word Ptr 88 // same as above
JMP @exit
LOOP16 @loop
Memory and immediate operands can be either absolute or relocatable.
An operand is absolute if its value or offset is entirely known during
compilation. An operand is relocatable if its offset will become known
only during linking.
- 2.3.10. -
