Write a C program to create and include your custom header file. How to create and include your own header file in C programming. C program to include another C program and custom header files.
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C preprocessor directives – #include, #define, #undef and conditional directives
A C preprocessor is a statement substitution (text substitution) in C programming language. It instructs the C compiler to do some specific (required) pre-processing before the compilation process.
When we compile a C program, C preprocessor processes the statements which are associated with it and expand them to make the code for further compilation.