The conditional preprocessor directive ____ means "if defined".

A) #ifdef
B) #ifndef
C) #ifdefined
D) #if_def

#ifdef

A preprocessor directive used in C and C++ programming to conditionally compile code if a specified macro is defined.

Preprocessor Directive

A command that is executed by the compiler before actual compilation begins, instructing it to perform specific operations such as including other files or defining constants.