USES Operator

The USES operator, coupled with the PROC directive, lets you list the names of all registers modified within a procedure. It performs two tasks:
  1. Generate PUSH instructions that save the registers on the stack at the beginning of the procedure.
  2. Generate POP instructions that restore the register values at the end of the procedure.
The USES operator immediately follows PROC, and is itself followed by a list of registers on the same line separated by spaces or tabs (not commas).

 Converting Lowercase Letters into Uppercase Letters by Using 
 PUSHAD Instruction   USES Operator  
 INCLUDE Irvine32.inc
 .data
 buffer  BYTE  64 DUP (0)
 .code
 main PROC
     mov   edx, OFFSET buffer
     mov   ecx, (SIZEOF buffer) - 1
     call  ReadString
     mov   esi, OFFSET buffer
     mov   ecx, LENGTHOF buffer - 1

 L1: cmp   BYTE PTR [esi], 'a'
     jl    L2
     cmp   BYTE PTR [esi], 'z'
     jg    L2
     call  convert
 L2: inc   esi
     loop  L1

     mov   edx, OFFSET buffer
     call  WriteString
     exit
 main ENDP

 convert PROC


     

      
     
      
      
    
    
    
      

     

    
     mov   cl, [esi]
     sub   cl, 'a'
     add   cl, 'A'
     mov   [esi], cl
     popad
     ret
 convert ENDP

 END main
 
 INCLUDE Irvine32.inc
 .data
 buffer  BYTE  64 DUP (0)
 .code
 main PROC
     mov   edx, OFFSET buffer
     mov   ecx, (SIZEOF buffer) - 1
     call  ReadString
     mov   esi, OFFSET buffer
     mov   ecx, LENGTHOF buffer - 1

 L1: cmp   BYTE PTR [esi], 'a'
     jl    L2
     cmp   BYTE PTR [esi], 'z'
     jg    L2
     call  convert
 L2: inc   esi
     loop  L1

     mov   edx, OFFSET buffer
     call  WriteString
     exit
 main ENDP




     

      
 
      
      
    
    
    
      

     

    
     mov   cl, [esi]
     sub   cl, 'a'
     add   cl, 'A'
     mov   [esi], cl
     ret
 convert ENDP

 END main