Getting Started

In-line assembler code integrates with the rest of a Pascal program. You declare variables as normal and output as normal but write assembler language in a block between the keywords asm and end. We use Intel syntax in the first of each pair of programs and have tested these programs in Lazarus and Delphi 7. The directive {$ASMMODE INTEL} is required in Lazarus but is not accepted by Delphi, so Delphi users should comment out or delete this line. The second program of each pair, in AT&T syntax, has an A appended to its name. The following table summarises important differences between the syntaxes. The EAX register is the accumulator and the mnemonic MOV is a slight abbreviation for 'move'.

	Intel syntax	Intel example	AT&T syntax	AT&T example
Registers	No prefix	EAX	Leading %	%EAX
Order of operands	Destination followed by source	MOV EAX, 5	Source followed by destination	MOV $5, %EAX
Literal values	No symbol for denary	MOV EAX, 5	$ indicates value (not address)	MOV $5, %EAX
Hex value	Leading $	$A	Leading $0x	$0xA
Binary value	Trailing b	101b	Leading $0b	$0b101
Labels	Leading @, Trailing :	@Start:	Leading .L, Trailing :	.LStart:
Indirect operands	Square brackets	MOV [EAX], 5	Rounded brackets	MOV $5, (EAX)
Indexing symbol	+	[ECX + ByteArray]	None or ,	ByteArray (%ECX) (%ECX,%EAX)
Operand size	May be included	MOV AL, byte ptr MyByte	Mnemonic may have suffix	MOVB MyByte, %AL

Follow these links to demonstration programs to learn more about in-line assembler code.

In-line assembler with Intel and AT&T syntax, addressing methods and encryption