Header file stdio.h
stdlib.h
sting.h
Learn the first three header files first.
1： stdio.h This header file contains various functions of the program interacting with external data.
To put it plainly, it is used to process input / output.
2：stdlib.h Standard library standard library header file
Contains some functions that deal with the system.
3：string.h Contains some character processing functions.
Since it is a character, the basic unit of processing is a byte, that is, 8 bits 0000 000 – – – 1111 1111 char 0 – 255