gistfile1.asm

if (x >= y)   #A label
    x=x-y;
else
    y=y-x

.data
x: word;
y: word;

//Machine Code
//Symbol table

Symbol   Address
x        0000 0000 0101  (5)   
y        0000 0000 0110  (6)
else     0000 0001 0011 (19)
then     0000 0001 0111 (23)
endif    0000 0001 1000 (24)

.instruction
    LOD x //AC=x
    SUB y //AC=x-y
    JPO then //jump to then if AC >= 0, i.e., if x >= y
else:
    LOD y //AC=y
    SUB x // AC=y-x
    STO y // y=AC=y-x
    JMP endif //skip the then-part
then:
    STO x //x=AC-x-y
endif: //code that follows the if statement


//Actual code      binary machine code (OPCODE - ADDRESS)
    LOD 5          0000 0000 0000 0101
    SUB 6          0011 0000 0000 0110
    JPO 23         0100 0000 0001 0111
    LOD 6          0000 0000 0000 0110
    SUB 5          0011 0000 0000 0101
    STO 6          0001 0000 0000 0110
    JMP 24         0110 0000 0001 1000
    STO 5          0001 0000 0000 0101


//High-level
k = 5;
while (i <= 99) i = i+k;

//Asm
.data
k: word
i: word

.instruction
     LOC 5     //AC=5
     STO k     //k=5
while:
     LOC 99 //AC=99
     SUB i     //99-i
     JNG exit  //loop exits if i <= 99
loopbody:
     LOD i   //AC=i
     ADD k   //AC=i+k
     STO i   //i=AC=i+k
     JMP while
exit (25):


Symbol table
Symbol    Address
k         0000 0000 0101 (5)
i         0000 0000 0110 (6)
while     0000 0001 0010 (18)
exit      0000 0001 1001 (25)

Assembly code     machine code
LOC 5             1011 0000 0000 0101
STO k             0001 0000 0000 0101
LOC 99            1011 0000 0110 0011
SUB i             0011 0000 0000 0110
JNG exit          0111 0000 0001 1001