# Include & lt; & gt; and # include,

# Include <> and # include,

I. # include <>

# Include <> references the header file in the compiler's class library path.

If the built-in header file defined by your compiler is referenced under C: \ Keil \ c51 \ INC \, then # include <stdio. h> C: \ Keil \ c51 \ INC \ stdio is referenced. h this header file, no matter what directory your project is in, C: \ Keil \ c51 \ INC \ stdio. h. The path is fixed. Generally, some header files, such as stdio, are referenced. h. conio. h, string. h. stdlib. h and so on.

Ii. # include <>

# Include "refers to the header file in the relative path of your program directory.

If your project directory is in D: \ Projects \ tmp \, then # include "my. h "references D: \ Projects \ tmp \ my. h this header file is generally used to reference some header files written by yourself. If # include "" is used, it will first find whether there is a corresponding header file in the current directory of your project. If not, it will still find the corresponding header file in the corresponding reference directory. For example, use # include "stdio. h "if there is no stdio in your project directory. h. The header file will still be located in C: \ Keil \ c51 \ INC \ stdio. h.