Differences between variable declaration and definition

Crazyspopcorn

Not to mention the direct focus:

If you divide a program into multiple files, you need to include code in some files. For example, a header file is contained in another header file, if a variable is defined as 2 .. Errors reported by the compiler

Error variable redefinition I believe many people have seen

Variable Declaration

Specifies the type and name of the variable. The definition is the same as that of the variable. However, in addition, the definition also applies for a bucket, and the variable may be assigned an initial value;

If you want to declare a variable rather than define it, add the keyword extern before the variable name and do not display the value of the initialization variable.

Extern int I; // declare I instead of defining I. No memory space is allocated for Int J; // declare and define J and allocate space for J

Differences between variable declaration and definition