(NASM / Assembly) Please explain in one english sentence what this program does?

Question

(NASM / Assembly) Please explain in one english sentence what this program does? (E.g., this program computes the sum of two numbers.. etc.)

segment .data

   msg1   db   “> “, 0

   msg2   db   “Results:”, 0

segment .text

   global asm_main

asm_main:

   enter    0,0   ;setup

   pusha

   ;;;;;;;;;;

   mov   eax, msg1

   call   print_string

   call   read_int

   mov   ebx, eax

   mov   dl, 9

for:  

   mov   eax, msg1

   call    print_string

   call   read_int

   cmp   eax, ebx

   jnl   nope

   mov   ebx, eax

nope:

   cmp   eax, ecx

   jl   nope2

   mov   ecx, eax

nope2:

   dec   dl

   jnz   for

   mov   eax, msg2

   call    print_string

   mov   eax, ecx

   sub   eax, ebx

   call    print_int

   call   print_nl  

   ;;;;;;;;;;;;;;;;;

   popa

   mov   eax, 0

   leave

   ret

Explanation / Answer

The above mentioned Assembly language programs computes two numbers. Segment .data is use to allocate a memory store the data. msg is used to print the following given in ' '. Segment .text is an code segment where the instructions are set in the memory. And global is used for a linker that uses to know where we are starting particular link. Enter is used to create a stack frame where as Leave is used to destroy the stack frame. pusha is basically a Push All General Registers where pusha is used to store or hold the values. Similarly popa is used to restore the state or register after pusha is called. mov eax,0 this represents 0 is stored in the eax. ret is nothing but a return. cmp is used to compare both the values.jnl refers jump if not less.jl refers jump if less jnz refers jump if not zero. dec refers decrement by one. sub means subtract (sub a,b refers b-a). So over all each and every line in the code commands here are the details. Hope so it is clear. As we First they are allocating memory then allocating some segment in that memory. And later linking it. Then pusha, there doing operations like move and call. Later using for loop and performing until jnl. And then comparing and jumping if less and doing decrement by 1. And performing same until jnz and later performing mov, sub and call. And restoring in popa and the. Mov eax to 0,l eave and return.

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