make print_dec clearer

.gitignore

@@ -1,2 +1,3 @@
 *.o
 a.out
+solution

02/main.s

@@ -123,34 +123,42 @@ pop ecx
 pop ebx
 ret
 
-; i hate this
+; input in EAX, all regs unmodified
 print_dec:
+pushad ; save regs
+; max 4294967296 is 10 chars
+; round to nearest 32-bit boundary
 sub esp, 12
-lea ecx, [esp+11]
+; string in ECX, length in EDX
+lea ecx, [esp+11] ; last possible byte
+; check for 0
 test eax, eax
 jz .zero
-mov esi, 0
+mov ebx, 10 ; base 10
-mov ebx, 10
+xor esi, esi ; counter
 .div_shit:
 xor edx, edx
+; divide
 div ebx
-dec ecx
+dec ecx ; next char
 inc esi
+; store
 add dl, '0'
 mov byte [ecx], dl
+; check if done
 test eax, eax
-jnz .div_shit
+jnz .div_shit ; continue
-mov edx, esi
+mov edx, esi ; counter in edx
 jmp .write
 .zero:
-mov byte [esp+10], 0
+mov byte [ecx], '0'
-lea ecx, [esp+10]
+mov edx, 1 ; length
-mov edx, 1 ; count
 .write:
 mov eax, 4 ; write
 mov ebx, 1 ; stdout
 int 0x80
-add esp, 12
+add esp, 12 ; restore stack
+popad ; restore regs
 ret
 
 [section .data]