Why output of int 070 is 56 in C program?

Question

Can you explain it? Why it given 56 value as output?

#include <stdio.h> 
#include <conio.h>

void main()
{
    int x = 070;
    printf("%d", x);
    getch();
}

If the language was being designed these days, I wonder if they'd still use the `0` prefix for octal? I think my favored alternative would be `0k`/`0K`. (`0o` or `0O` would be too confusing.) — Ian Abbott, Apr 15 '16 at 14:45

score 16 · Accepted Answer · edited Jun 20 '20 at 09:12

16

Any integer literal (integer constant) starting with 0 is an octal representation.

Quoting C11, chapter §6.4.4.1, Integer constants

octal-constant:

0
octal-constant octal-digit

and

octal-digit: one of
  0 1 2 3 4 5 6 7

and, as per chapter §7.21.6.1, for %d format specifier with printf(), (emphasis mine)

d,i The int argument is converted to signed decimal [...]

edited Jun 20 '20 at 09:12

Community

answered Apr 15 '16 at 14:33

Sourav Ghosh

1 Answers1