Updated: 04/02/2019 by Computer Hope

A macro (which stands for "macroinstruction") is a programmable pattern which translates a certain sequence of input into a preset sequence of output. Macros can make tasks less repetitive by representing a complicated sequence of keystrokes, mouse movements, commands, or other types of input.

In computer programming, macros are a tool that allows a developer to re-use code. For instance, in the C programming language, this is an example of a simple macro definition which incorporates arguments:

#define square(x) ((x) * (x))

After being defined like this, our macro is used in the code body to find the square of a number. When the code is preprocessed before compilation, the macro will be expanded each time it occurs. For instance, using our macro like this:

int num = square(5); the same as writing:

int num = ((5) * (5));

…which declares an integer type variable named num, and set its value to 25.


A macro is not the same as a function. Functions require special instructions and computational overhead to safely pass arguments and return values. A macro is a way to repeat frequently-used lines of code. In some simple cases, using a macro instead of a function can improve performance by requiring fewer instructions and system resources to execute.

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