What is the difference between variable declaration and definition in C/C++?

Declaration provides an identify of a variable to the compiler, saying “Hey, there is a variable with certain type here.”

Definition creates a memory space for the variable, which is used to store the data.

The differences are:

1. Declaration does not create memory space but definition does.

2. Same variable may have multiple declaration(external variable), but it can have only one definition.

We can make a declaration and definition at one time, like

int a=1;

 

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