Difference between function definition and function declaration

Difference between  function definition and function declaration

DECLARATION	DEFINITION
A variable or a function can be declared any number of times	A variable or a function can be defined only once
Memory will not be allocated during declaration	Memory will be allocated
int f(int); The above is a function declaration. This declaration is just for informing the compiler that a function named f with return type and argument as int will be used in the function.	int f(int a) {   return a; } The system allocates memory by seeing the above function definition.

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