Using with atoi() in C

Question

I'm trying to use atoi() but I need the 0 in the front, but the function ignores it

  sprintf(str, "%d%d%d%d",comp[cont][0],comp[cont][1],comp[cont][2],comp[cont][3]);
  conv=atoi(str);  

  printf("%d \n",conv);  

When I print str: 0100
And conv: 100
Is there any way to show the 0?

Answer 1

It's because integers simply doesn't have zeros in front of them.

You need to print it with that:

printf("%04d \n",conv);

You might find e.g. this printf reference useful.

Answer 2

Just change the printf format:

printf("%04d \n",conv);  

Answer 3

Just append the zero while printing. Try the following

print("0%d\n", conv);

Answer 4

Why so complicated and not just do directly:

printf("%d%d%d%d", comp[cont][0], comp[cont][1], comp[cont][2], comp[cont][3]);