Home : Software Terms : Function Definition


In mathematics, a function is defined as a relationship between defined values and one or more variables. For example, a simple math function may be:

y = 2x

In this example, the relationship of y to x is that y is twice as much as the value assigned to x. While math functions can be far more complex than this, most are simple relative to functions used in computer programming. This may be why math functions are often referred to as "expressions," while computer functions are often called "procedures" or "subroutines."

Computer functions are similar to math functions in that they may reference parameters, which are passed, or input into the function. If the example above were written as a computer function, "x" would be the input parameter and "y" would be the resulting output value. It might look something like this:

function double(x)
  $y = 2 * x;
  return $y;

The above example is a very basic function. Most functions used in computer programs include several lines of instructions and may even reference other functions. A function may also reference itself, in which case it is called a recursive function. Some functions may require no parameters, while others may require several. While it is common for functions to return variables, many functions do not return any values, but instead output data as they run.

Functions are sometimes considered the building blocks of computer programs, since they can control both small and large amounts of data. While functions can be called multiple times within a program, they only need to be declared once. Therefore, programmers often create "libraries" of functions that can referenced by one or more programs. Still, the source code of large computer programs may contain hundreds or even thousands of functions.

Updated: December 28, 2010

Cite this definition:


TechTerms - The Tech Terms Computer Dictionary

This page contains a technical definition of Function. It explains in computing terminology what Function means and is one of many software terms in the TechTerms dictionary.

All definitions on the TechTerms website are written to be technically accurate but also easy to understand. If you find this Function definition to be helpful, you can reference it using the citation links above. If you think a term should be updated or added to the TechTerms dictionary, please email TechTerms!

Subscribe to the TechTerms Newsletter to get featured terms and quizzes right in your inbox. You can choose to receive either a daily or weekly email.

Sign up for the free TechTerms Newsletter

How often would you like to receive an email?

You can unsubscribe at any time.
Questions? Please contact us.