Execution
always begins, at the first statement of the program. Statements are executed
one at the time, in order from top to bottom. Function definitions do not alter the flow of
execution of the program, but remember that statements inside the function are
not executed until the function is called. A function call is like a detour in
the flow of execution. Instead of going to the next statement, the flow jumps
to the body of the function, then executes all the statements and then comes
back to pick up where it left off.
If
there is another or second function call inside the first function definition,
then execution of the program jumps to the definition of a second function from
the first function and then comes back to the first function and executes the
first function and after returns the value and finishes the execution of the
program. We know it’s a little bit confusing but it’s very common thing that
can happen in larger programs.
Programming
languages in general are good at keeping track of where it is, so each time a
function completes, the program picks up where it left off in the function that
called it. When it gets to the end of the program, it terminates. So when you
read a program it’s good practice to follow the flow of execution rather than
read it from top to bottom.
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