Manipulating x86-32 Flags

Here is a sample program to demonstrate how the respective flags are affected by each ADD, SUB, INC, DEC, and NEG instructions.

.386
.model flat,stdcall
.stack 4096
ExitProcess proto,dwExitCode:dword

.data
Rval SDWORD ?
Xval SDWORD 26
Yval SDWORD 30
Zval SDWORD 40

.code
main PROC
  ; INC and DEC
  mov ax,1000h
  inc ax ; 1001h
  dec ax ; 1000h
  ; Expression: Rval = -Xval + (Yval - Zval)
  mov eax,Xval
  neg eax                  ; -26
  mov ebx,Yval
  sub ebx,Zval             ; -10
  add eax,ebx
  mov Rval,eax             ; -36
  ; Zero flag example:
  mov cx,1
  sub cx,1                 ; ZF = 1
  mov ax,0FFFFh
  inc ax                   ; ZF = 1
  ; Sign flag example:
  mov cx,0
  sub cx,1                 ; SF = 1
  mov ax,7FFFh
  add ax,2                 ; SF = 1
  ; Carry flag example:
  mov al,0FFh
  add al,1                 ; CF = 1, AL = 00
  ; Overflow flag example:
  mov al,+127
  add al,1                 ; OF = 1
  mov al,-128
  sub al,1                 ; OF = 1
INVOKE ExitProcess,0
main ENDP
END main