Some knowledge of the initial C language

Preface

I'm learning c Language , We will be right. c Make a general understanding of each classification knowledge of language , This paper will introduce several classification knowledge （ Follow up will continue to supplement ）

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  One . first c Language program , Please look at the chart below.

Here main Function is the entry of the program , There is and only one in a project main function .

And the first 6 Yes printf The function is a print function , That is, output... On the screen “   ” Content between , The result of the program is ：

Two . data type

    1. Data types are used to define variables ,c The language mainly provides the following data types ：

2. The space occupied by each data type

  Look at the following procedure ：

  Here sizeof keyword , It means to calculate the memory occupied by an object , Unit is byte, The following are the output results ：

 1 2 4 4 8 4 8（ In the order shown above ） That is, the memory size occupied by each data type .

3、 ... and . Variables and constants

1. Variable

Variables are literally variable quantities , The method of defining variables is shown in the figure below ：

 （ It is recommended to assign initial values to variables when creating them .）

2. Classification of variables

There are two kinds of variables , One is local variable , One is Global variables .

For local variables ： Is defined in braces （ Code block ） The variables in are local variables .

For global variables ： Variables defined outside braces are global variables , Please look at the chart below. ：

 by the way： When the variable names of local variables and global variables are the same , Local variables take precedence ：

example ：

The above is the initial c Part of the knowledge of language , Subsequent updates will continue ！