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Chapter 10. Programming Style and Techniques
The method you use for constructing your programs is just as important as the language you use to write
them.
Consider the Data
When you are faced with the task of writing a program, the first thing to consider is the data you are
required to process. Make a list of the input data—what are the items and what are the possible values of
each? If the items have a kind of structure or pattern, draw a diagram to illustrate it. Then do the same for
the output data. Study your two diagrams and try to see if they fit together. If they do, you are well on the
way to designing your program.
Next, write the specification that the user will use. This might be a written specification, a HELP file or
both.
Last of all, write your program.
Here is a little example:
You are required to write an interactive program that invites the user to play “Heads or tails”. The game
can be played as long as the user likes. To end the game the user should reply Quit in answer to the
question “Heads or tails?” The program is arranged so that the computer always wins.
Think about how you would write this program.
The computer starts off with:
Let's play a game! Type "Heads", "Tails",
or "Quit"
and press ENTER.
This means that there are four possible inputs:
v HEADS
v TAILS
v QUIT
v None of these three.
And so the corresponding outputs should be:
v Sorry. It was TAILS. Hard luck!
v Sorry. It was HEADS. Hard luck!
v That's not a valid answer. Try again!
And this sequence must be repeated indefinitely, ending with the return to CICS.
Now that you understand the specification, the input data and the output data, you are ready to write the
program.
If you had started off by writing down some instructions without considering the data, it would have taken
you longer.
Test Yourself...
Write the program. If you are careful, it should run the first time!
© Copyright IBM Corp. 1992, 2009 89