Hi
I am new in assembley and I need a sample source or a tutorial about mul of big numbers

for example 10 disigts * 10 digits.

And?

The tutorial is "can you do this on paper"?

So write the steps out on paper, and think about turning it into operations you can implement on a computer.

13
*57

So you start with 3*7, result is 21. The 1 is one part of the result, which you do something with, and the 2 is another part of the result which you do something else with.

Throw in a couple of loops, and you're nearly there.

An example of such case would be

MOV A,#25H
MOV B,#65H
MUL AB

where A has 25H and B has 65H and just use the MUL function to multiply both but you must only use A and B registers. The results will be saved in register A.