Programming: Returning a Value/Values from a Subroutine

Overview of Returning Values from a Subroutine

A subroutine in programming is a sequence of program instructions that perform a specific operation, packaged as a unit that can be used repeatedly in a program.
Subroutines can be functions (which return a value) or procedures (which perform an action but don’t return a value).
When a function finishes executing, it can return a value back to the point from which it was called. This is achieved with the use of a return statement.
A return statement causes the program control to transfer back to the caller of the subroutine.

Using the Return Statement

In most programming languages, the return keyword is used to exit from the subroutine and to optionally return a value.
For example, in Python, the syntax would be: return expression
Here ‘expression’ refers to the value or set of values you want to return. If no expression is provided, None is returned.
The function stops executing as soon as it encounters a return statement, even if it’s not at the end of the function.

Returning Multiple Values

Certain programming languages like Python allow functions to return multiple values.
These values can be returned either as separate return statements, a tuple, a list, or a dictionary.
This allows complex data to be efficiently and tidily returned from a subroutine.

Importance of Returning a Value

The use of return value functionality allows for modular programming, making code more reusable, functionally segregated, and easier to read and maintain.
The returned value can be used as an input for another function, assigned to a variable, printed out, and more.
Subroutines with return values allow for better testing and debugging since you can easily check the returned result for correctness.

Python Example

In Python, a function that adds two numbers and returns the result may look like this:

def add_numbers(num1, num2):
    sum = num1 + num2
    return sum

In the example above, the function add_numbers takes two parameters (num1 and num2), calculates their sum, and then returns the sum as the result.

Remember, understanding the mechanics of returning values from a subroutine is essential for writing efficient and modular code.