The Assembly Programming Master Book

The constructs in the next two sections are converted to the microprocessor command in the course of assembling.

Conditional Constructs

1. .IF condition ... .ENDIF

2. .IF condition ... .ELSE ... .ENDIF

3. .IF condition 1 ... .ELSEIF condition 2 ... .ELSEIF condition 3 ... .ELSE ... .ENDIF

Consider the following fragment containing a conventional construct and the corresponding Assembly code:

.IF EAX==12H MOV EAX,'10H .ELSE MOV EAX, 15H .ENDIF

The preceding fragment is equivalent to the following Assembly code:

CMP EAX, 12H JNE NO_EQ MOV EAX, 10H JMP EX_BLOK NO_EQ: MOV EAX, 15H EX_BLOK:

It is rather convenient . However, do not be too enthusiastic about it because, in my opinion, this will carry you from the art of Assembly language programming.

The WHILE Loop

.WHILE condition ... .ENDW

For example:

WHILE EAX<64H ADD EAX, 10H ENDW

For MASM, the following is used:

JMP L2 L1: ADD EAX, 10H L2 CMP EAX, 64H JB L1

For TASM, the following is used:

L1: CMP EAX, 64H JNB EXI ADD EAX, 10H JMP L1 EXI:

There is a minor differences related to how the two assemblers translate the .IF and .WHILE directives. TASM32 automatically optimizes the code by adding extra no-operation ( NOP ) commands to align by the quadruple word boundary. This makes the program execution somewhat faster but increases its size . I prefer the MASM attitude.