How to write assembly code for flow chart

Why in assembly???

Don't get me wrong assembly is a very powerful low level programming language but it is difficult and the programs written in it are long and require deep understanding of embedded programming. It also fluctuates (it's syntax changes) on different processor architectures so the program compatibility with OS or computer itself is hard to reach. Don't try to write assembly code unless you really know what you are doing, instead choose higher level programming language like C or C++ that supports low level functionally which I'm assuming you need since you talk about assembly.