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UINT_MAX in C

Posted on 23 Apr 2014

Quick tip: You can also get UINT_MAX in C by doing (unsigned) -1.

Why does this work? In C, negative numbers are stored in Two’s complement representation.

In this representation, signed numbers use the highest bit, the sign bit, to store the sign of the number. Negation is done by flipping all bits and adding

  1. In unsigned 4-bit numbers, 1 would look like 0001, while -1 would be 1110 + 1 = 1111, the maximum 4-bit number.

This StackOverflow question notes that C believes unsigned 1 0001 is less than signed -1 1111, again due to the internal representation.

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