Standard C language summary 1

One . The header file :  With .h ending , It stores auxiliary code , Most of them are descriptions of functions

 #include The function is to import header files

           #include <xxx.h>

                <> Find the header file from the path specified by the system and import

          #include "xxx.h"

                "" First find the header file from the current working path , If it cannot be found, find and import from the path specified by the system

main function : The caller of the function is the operating system , Its return value is given to the operating system , Its value can reflect how the program ends , There are generally three types ：

         Positive numbers     Something unusual happened    ( The mistakes of others )

        0       Everything is all right

        negative     There is an error    ( Your own mistakes )

C File type of language ：

    .c Source file

    .h The header file

    .h.gch Compilation result file of header file , It will be used preferentially

    .i Preprocessing files

    .s Assembly files

    .o Target file

    .a Static library files

    .so Shared library file

Branch statement

    if( expression )  // Single branch

    {

        // Expression is true ( Nonzero ), Then execute the code here

    }

    else // Double branch

    {

        // Expression is false ( zero ), Then execute the code here

    }

   

    if( expression 1)  // Multiple branches

    {

        // expression 1 It's true , Then execute the code here

    }

    else if( expression 2)

    {

        // expression 2 It's true , Then execute the code here

    }

    else

    {

        // If all the above expressions are false , Then finally execute the code here

    }

1. Automorphic operator : ++/--

2. Arithmetic operator :+ - * / %

3. Relational operator :> < >= <= == !=

4. Logical operators : && || !

5. Ternary operator : a?b : c

The priority of each operator is in order