Answer:
In a function prototype the heading is followed by a semicolon, whereas in a function definition the heading is followed by a function block.
Explanation:
As the function prototype only declares the function and the function definition defines the operations in the function.
e.g:
add(int x, int y); is the prototype
add(int x, int y)
{
int sum;
sum x
y;
} is the function definition.