Definition, synonyms and related words
A construct in source code that allows another part of the code to run only if a specified identifier is defined in the program.
"The programmer used an ifdef directive to ensure that the debugging functions were executed only when the DEBUG flag was defined during compilation."
In plain English: An ifdef is a command that tells a computer program to only run certain parts of code if a specific condition has been set up beforehand.
"The programmer added an ifdef statement to handle code that might not run on older devices."
Usage: Use ifdef as a noun when referring specifically to the preprocessor directive itself, such as saying "the compiler processes an ifdef statement." Do not use it interchangeably with #ifdef or other syntax variations; instead, describe the entire line of code using terms like "preprocessing instruction" or simply quote the symbol.
The term ifdef is a contraction of the phrase "if defined," used as a command to check whether a specific variable or macro exists before compiling code. It entered English through computer programming rather than evolving from an older word with the same meaning.