The idiv instruction divides the contents of the 64 bit integer EDX:EAX ( constructed by viewing EDX as the most significant four bytes and EAX as. As complete 32-bit data registers: EAX, EBX, ECX, EDX. The X means pair, and goes back to at least the 8080. Intel assembly has 8 general purpose 32-bit registers: eax, ebx, ecx, edx, esi, edi, ebp, esp. A feature of assembly language is that each line in the source code usually contains a single instruction to the processor, for example MOV EAX,EDX will move. For another example, addl %edx,%eax means Add the contents of the edx and eax registers, and place the sum in the eax register.