In computing, a fixed point presentation is a computer presentation for a (non-integer) number that has a fixed number of digits after the decimal (or binary or hexadecimal) point. For example, a fixed point number with 4 digits after the decimal point could be used to store numbers such as 1.3467, 281243.3234 and 0.1000, but would round 1.0301789 to 1.0302 and 0.0000654 to 0.0001.
In mathematics, a fixed point of a function is a point which is mapped to itself by the function. For example, if f is defined on the real numbers by f(x) = x2 - 3x + 4, then 2 is a fixed point of f, because f(2) = 2. See also Brouwer Fixed Point Theorem and contraction mapping.