printf with “%d” of numbers starting with 0 (ex “0102”) giving unexpected answer (ex ‘”66″)

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This is because when the first digit of a number (integer constant) is 0 (and second must not be x or X), the compiler interprets it as an octal number. Printing it with %d will give you a decimal value.
To print octal value you should use %o specifier 

   printf("%o", n);

6.4.4.1 Integer constants:

  1. An integer constant begins with a digit, but has no period or exponent part. It may have a prefix that specifies its base and a suffix that specifies its type.

  2. A decimal constant begins with a nonzero digit and consists of a sequence of decimal
    digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
    digits 0 through 7 only    . A hexadecimal constant consists of the prefix 0x or 0X followed
    by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
    10 through 15 respectively.

Integer Constants:

1.Decimal constants: Must not begins with 0. 

 12  125  3546

2.Octal Constants: Must begins with a 0. 

 012 0125 03546

3.Hexadecimal Constants: always begins with 0x or 0X. 

 0xf 0xff 0X5fff

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