Slide 12.2: LOOPNZ and LOOPNE instructions
Slide 12.4: Decision directives
Home

Conditional Structures

A conditional structure is one or more conditional expressions that trigger a choice between different logical branches. Each branch causes a different sequence of instructions to execute. There are many ways to implement a compound expression. The following code shows some of the ways. 

  if (opnd1 is even)
     and (opnd2 is odd)
  then print (opnd1 - opnd2)
  else print (opnd1 + opnd2)
 
  ebx = 0
  while (opnd < 8)
     ebx += opnd
  print ebx
 
 INCLUDE Irvine32.inc
 count = 10
 .code
 main PROC

     ; Generate the opnd1.
     call   Randomize
     mov    eax, count
     call   RandomRange
     call   WriteDec
     mov    ecx, eax

     ; Generate the opnd2 < opnd1.
     cmp    eax, 0
     jne    L0
     inc    eax
 L0: call   RandomRange
     mov    edx, eax
     test   cl, 00000001b

   

    
       
     
     

    
    
    

 
     

     		
    

   
     ; opnd1 is even

     test   dl, 00000001b
     jz     L1
     ; opnd2 is odd

     ; The THEN part
     mov    al, '-'
     call   WriteChar
     sub    ecx, edx
     jmp    L2

     ; The ELSE part
 L1: mov    al, '+'
     call   WriteChar
     add    ecx, edx

 L2: mov    eax, edx
     call   WriteDec
     mov    al, '='
     call   WriteChar
     mov    eax, ecx
     call   WriteDec
     exit
 main ENDP
 END main
 
 INCLUDE Irvine32.inc
 .data
 count = 10
 TRUE  = 1
 FALSE = 0
 First  BYTE  TRUE
 .code
 main PROC
     call   Randomize
     mov    ebx, 0

 L1: ; Generate the opnd.
     mov    eax, count
     call   RandomRange
     mov    ecx, eax
     test   cl, 11111000b

   

    
       
     
     

    
    
    

 
     

     		
    

   
     ; opnd < 8

     cmp    First, TRUE
     je     L2
     mov    al, '+'
     call   WriteChar

 L2: mov    First, FALSE
     mov    eax, ecx
     call   WriteDec
     add    ebx, ecx
     jmp    L1

     ; Check the condition 0 = 0
 L3: cmp    First, TRUE
     jne    L4
     mov    eax, 0
     call   WriteDec

 L4: mov    al, '='
     call   WriteChar
     mov    eax, ebx
     call   WriteDec
     exit
 main ENDP
 END main