How do Leading Zeros Affect Numeric Constants in C/C ?

Numeric Constants with Leading Zeros in C/C

When a numeric constant in C or C is prefixed with a zero ('0'), it denotes an octal (base 8) number. This prefix doesn't apply to binary or hexadecimal constants, which use specific syntax (e.g., 0b and 0x prefixes).

In the example provided, the numeric constant 0123 is interpreted as an octal number. In octal, each digit represents a power of 8. The number can be converted to decimal by multiplying each digit by its respective power of 8 and summing the results:

0 * 8^3 = 0
1 * 8^2 = 64
2 * 8^1 = 16
3 * 8^0 = 3

Adding these values gives the decimal result of 83.

This behavior is defined by the C and C standards and is not specific to any particular compiler. The octal prefix allows programmers to represent numbers using the base 8 notation, which is often used in historical contexts or in hardware-related applications.

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