Instruction operand symbols

   r8           one of the byte registers al,cl,dl,bl,ah,ch,dh, or bh
   r16          one of the word registers ax,cx,dx,bx,sp,bp,si, or di
   r32 (386+)   one of the doubleword registers
                eax,ecx,edx,ebx,esp,ebp,esi, or edi

   rel8         a relative address (distance -128 to +127 bytes)
   rel16        a relative address within the same code segment

   imm8         an immediate signed byte value (-128 to +127)
   imm16        an immediate signed word value (-32,768 to +32,767)
   imm32 (386+) an immediate signed dword value
                (-2,147,483,648 to +2,147,483,647)

   r/m8         a one-byte operand that is either a byte register or
                a byte from memory
   r/m16        a word register or memory operand used for instructions
                whose operand-size attribute is 16 bits
   r/m32 (386+) a doubleword register or memory operand used for
                instructions whose operand-size attribute is 32 bits

   Sreg         a segment register