PS refers to "preprocessing statement", which is a special instruction in C language. This instruction tells the compiler to preprocess the source code file before compiling it. The preprocessor can modify the source code file by analyzing any preprocessing instructions contained in the source code file. Common ps include #include, #define and #ifndef, which can help programs to automatically insert specific header files and macro definitions at compile time and realize the function of code switching control.

C language is an efficient programming language, and the appearance of ps facilitates the compilation and development of C language. The preprocessor can modify the code file before compilation, and quickly realize the functions of automatic insertion of header files and on-off control of codes, which provides great convenience for programmers to write codes. At the same time, the preprocessor can also customize macro definitions, so that programmers can use these macro definitions directly at compile time to simplify the code and improve the readability and maintainability of the code.

In the development of C language, preprocessor is widely used in automatic insertion of code header files, conditional compilation and macro definition. Perhaps the most common is the #include directive, which can automatically insert the specified header file. In addition, #define can define a macro, and when calling the macro name in the code, it is essentially calling the definition of the macro name, thus simplifying and modularizing the code. You can also use #if or #ifndef instructions to realize conditional compilation, and logically divide the code into different modules, which can be compiled and executed under different conditions.