Hello,
I am beginning learning intel assembly. I am taking simple gcc programs and looking at the assembly. All gcc outputs have a line similar to:
mov DWORD PTR [ebp-4] that I can't figure out.
For example

int main(void)
{  
   int x = 5;
   return 0;
}

gives me

.file "test.c"
   .intel_syntax noprefix
   .text 
.globl main
   .type main, @function
main:
   push  ebp
   mov   ebp, esp ; memory address of start of stack
   sub   esp, 16  ; push for room for a word
   mov   DWORD PTR [ebp-4], 5 ; I'm confused here
   mov   eax, 0 ; retval of function
   leave
   ret
   .size main, .-main
   .ident   "GCC: (Ubuntu 4.4.1-4ubuntu9) 4.4.1"
   .section .note.GNU-stack,"",@progbits

I know it is putting the value of 5 on the stack, but why at ebp-4? A word is 2 bytes or 16 bits. Is the 4 in bits or bytes? Since, gcc has subtracted 16 from the esp, why not put it at ebp?

Thanks

Its being used to access local vars.

sub esp, 16
The stack pointer has 16 subtracted from it to reserve room
for 4 doublewords as local variables on the stack.
mov DWORD PTR [ebp-4], 5
Copies 5 into first doubleword on the stack.

Take a look at the stack at this point:
XXXXXXXXXXXXXXXXX] - 16 <--- ESP points here
XXXXXXXXXXXXXXXXX] - 12
XXXXXXXXXXXXXXXXX] - 8
XX XX XX XX XXXXXXX] - 4 Beginning of Local Vars
PUSHED VALUE OF EBP] + 0 <--- EBP points here
RETURN ADDRESS XX ] + 4
XXXXXXXXXXXXXXXXX] + 8 Parameters usually begin here

commented: Nice +19