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cintdecimaloctal

Why output of int 070 is 56 in C program?

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();
}
Solution

  • 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 [...]

    Thereby, octal 70 == decimal 56.