Slide 5.5: Data definition statements (cont.)
Slide 5.7: Multiple initializers
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Defining BYTE and SBYTE Data 



     val0   SBYTE   50h+10h   ; integer expression


     val1   BYTE    'A'       ; character constant


     val2   BYTE    255       ; largest unsigned byte


     val3   SBYTE   -128      ; smallest signed byte


     val4   BYTE    ?         ; space allocated but not the value
Each initializer must be an 8-bit integer expression or character constant.
Type Usage
BYTE 8-bit unsigned integer
SBYTE 8-bit signed integer

 0 + (–10)  0 + 246  BYTE: (–10) + 20 


 .data


 X   BYTE  -10


 .code


 sub   eax, eax


 add   al, X


 call  DumpRegs
 


 .data


 X   BYTE  246


 .code


 sub   eax, eax


 add   al, X


 call  DumpRegs
 


 .data


 X   BYTE  -10


 Y   BYTE   20


 .code


 sub   eax, eax


 add   al, X


 add   al, Y


 call  WriteInt
 Output  Output  Output
  EAX =  



  EAX =  



   




 SBYTE: (–10) + 20  SBYTE: 10 + (–20)  MOVSX: 10 + (–20) 


 .data


 X   SBYTE  -10


 Y   SBYTE   20


 .code


 sub   eax, eax


 add   al, X


 add   al, Y


 call  WriteInt
 


 .data


 X   SBYTE   10


 Y   SBYTE  -20


 .code


 sub   eax, eax


 add   al, X


 add   al, Y


 call  WriteInt
 


 .data


 X   SBYTE   10


 Y   SBYTE  -20


 .code


 sub    eax, eax


 add    al, X


 add    al, Y


 movsx  eax, al


 call   WriteInt
 Output  Output  Output