Data

#ifndef

If a keyword or variable is not defined, then compile the following code

Syntax: #ifndef keyword or variable

keyword

Required. The keyword or variable to check

Notes:

When checking for a variable definition, the variable must be defined before the #ifdef directive

Example:

#ifndef testCode
  .....
#endif

Also See: #define, #undefine, #if, #ifdef, #else, #elseif, #endif