| Lesson 8 | Subprograms |
| Objective | Define a subprogram. |
What is Subprogram?
Earlier in this module it was stated that the primary philosophy of structured programming is to partition a large program into a number of smaller programs. Let's now look at a simple example of how this is done. Consider the GoForARide program from the previous lesson.
GoForARide
Put on cycling clothes
For 2 hours
Ride for 15 minutes
Drink from water bottle
Remove cycling clothes
Take a shower
The statement:
Drink from water bottle
seems pretty simple, but for the sake of discussion let's suppose that it involves the following.
If the water bottle is empty
Find a source of water
Open the water bottle
Fill it with water
Close the water bottle
Drink some water
Thus our GoForARide program really should be:
GoForARide2
Put on cycling clothes
For 2 hours
Ride for 15 minutes
If the water bottle is empty
Find a source of water
Open the water bottle
Fill it with water
Close the water bottle
Drink some water
Remove cycling clothes
Take a shower
This is starting to get a little complicated, so in order to simplify the program we might create a subprogram called DrinkFromWaterBottle that looks like:
DrinkFromWaterBottle
Subprogram: A program within a program. Also called a function, method, procedure, or subroutine.
If the water bottle is empty
Find a source of water
Open the water bottle
Fill it with water
Close the water bottle
Drink some water
And then call this subprogram from our GoForARide program as in the following (roll your cursor over the highlighted line of code to see a
graphic representation of this subprogram being executed):
Put on cycling clothes
For 2 hours
Ride for 15 minutes
Subprogram Execution
Making the task of drinking from the water bottle a subprogram has noticeably simplified the GoForARide program, but there is an additional benefit in that the DrinkFromWaterBottle subprogram
can be used in other programs as well. Imagine how this subprogram might be used in programs such as DoYardWork or GoForAHike.
The next lesson concludes our look at the fundamental concepts of structured programming.
Structured Programming Terms