DIV - x86-64 instruction reference

divUnsigned divide 
Divides the implicit unsigned dividend selected by the operand width, producing a quotient and remainder.
8086 and later
Intel's reference: DIV 
Used in Arithmetic, logic and bitsx86-64 assembly
Interrupts, exceptions and signalsx86-64 assembly
Multiply and divide, with the remainderx86-64 assembly
Print an unsigned number in bases 2 through 36x86-64 assembly
 
CFPFAFZFSFDFOF ?????–?
? undefined afterwards
– not changed
Forms  div  8163264 
Operands r/m A general-purpose register or memory location matching the operation’s size, for example rax or qword [rbp-8]. The byte registers ah, bh, ch and dh cannot be used with a REX prefix, including when the memory address uses r8–r15. 
The divisor width selects the implicit dividend, quotient and remainder:
Divisor widthDividendQuotientRemainder
8 bitsaxalah
16 bitsdx:axaxdx
32 bitsedx:eaxeaxedx
64 bitsrdx:raxraxrdx
The register before the colon is the high half. For a dividend that fits in the low half, clear the high half first; for example, xor edx, edx before div rcx. A zero divisor or a quotient too large for its destination causes a divide error. Flags are undefined. Use idiv for signed division.
 global _start

section .text
_start:
        mov rax, 100        ; the dividend is rdx:rax
        xor rdx, rdx        ; so the high half has to be cleared
        mov rbx, 7
        div rbx             ; quotient in rax, remainder in rdx

        mov rax, 60         ; syscall 60: exit
        xor rdi, rdi
        syscall
Divisor width	Dividend	Quotient	Remainder
8 bits	`ax`	`al`	`ah`
16 bits	`dx:ax`	`ax`	`dx`
32 bits	`edx:eax`	`eax`	`edx`
64 bits	`rdx:rax`	`rax`	`rdx`