What is the meaning of '#' in programming?

The '#' symbol in programming is commonly associated with preprocessor directives, particularly in languages like C and C++. Preprocessor directives provide mechanisms for the compiler to process certain instructions before the actual compilation of code begins. This can include instructions for including libraries, defining constants, or conditional compilation.

For instance, using #include tells the compiler to include the contents of a specific file or library in the current file being compiled. Similarly, #define allows you to define constants or macros.

Understanding this context is essential because it shows how the '#' serves as a tool to provide instructions that help set up the code environment before the main compilation process occurs, influencing how the code behaves based on those prior directives.