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C language variable

Define the situation in 3 of the variables

Defined at the beginning of the function.

Defined in a compound statement within a function.

Defined outside the function.

C language local variable

Variables defined within a function are valid only within the scope of this function, that is, they can only be referenced within this function, and these variables cannot be used outside this function.

Variables defined within a compound statement are valid only within the scope of the compound statement and can only be referenced within this compound statement. These comparisons cannot be used outside compound statements, and these are called "local variables".

Variables defined in the main function are also valid only in the main function, not in the entire file or program because they are defined in the main function.

Variables of the same name can be used in different functions. They represent different objects and do not interfere with each other.

Formal parameters are also local variables.

Within a function, variables can be defined in compound statements, which are valid only in this compound statement, also known as "subroutines" or "program blocks".

C language global variable

Variables defined within a function are local variables, while variables defined outside the function are called external variables, and external variables are global variables.

Global variables can be shared by other functions in this file.

The valid range of global variables is from the location where the variable is defined to the end of the source file.

The function of setting global variables is to increase the channel of data connection between functions.

In order to make it easier to distinguish between global and local variables, it is a habit among C programmers to capitalize the first letter of a global variable (unspecified).

Cases of global variables and local variables in C language

# include

Int num1=10; / / defines and initializes global variables

Int main ()

{

Int num2=20;// defines local variables

Printf ("% d\ n", num1); / / output the value of the global variable

Printf ("% d\ n", num2); / / output the value of the local variable

Return 0

}

Compile and run the result:

ten

twenty

-

Process exited after 0.06448 seconds with return value 0

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