A real number is any positive or negative number. This includes all integers and all rational and irrational numbers. Rational numbers may be expressed as a fraction (such as 7/8) and irrational numbers may be expressed by an infinite decimal representation (3.1415926535...). Real numbers that include decimal points are also called floating point numbers, since the decimal "floats" between the digits.
Real numbers are relevant to computing because computer calculations involve both integer and floating point calculations. Since integer calculations are generally more simple than floating point calculations, a computer's processor may use a different type of logic for performing integer operations than it does for floating point operations. The floating point operations may be performed by a separate part of the CPU called the floating point unit, or FPU.
While computers can process all types of real numbers, irrational numbers (those with infinite decimal points) are generally estimated. For example, a program may limit all real numbers to a fixed number of decimal places. This helps save extra processing time, which would be required to calculate numbers with greater, but unnecessary accuracy.
Updated: May 14, 2010