Why should EDX be 0 before using the DIV instruction?

Question

I noticed when EDX contains some random default value like 00401000, and I then use a DIV instruction like this:

mov eax,10
mov ebx,5
div ebx

Answer 1

The DIV instruction divides EDX:EAX by the r/m32 that follows the DIV instruction. So, if you fail to set EDX to zero, the value you are using becomes extremely large.

Trust that helps