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Incremental Programming

by John Dirk, Joh

Incremental Programming

Many
novice programmers start a program with a “big bang" approach, meaning
they want to write the whole program in one step and then only they
would try to compile and run. However as humans we maake many mistakes
when programming, especially given that we have to use a programming
language to do the job and most programming languages differ
drastically from natural languages. Because it is very likely that we
would make mistakes, we have to ensure that we leave room so that we
could easily identify the mistakes we have made.

Incremental Programming

Helps

The
solution to this situation is to adopt an incremental approach in
programming. The idea is to keep building your code using several small
working pieces. The pieces of code would not do a complete job. Rather
they will lay out the skeleton for the final complete program. Once you
are convinced the correct skeleton is in place, you could go on and add
muscle to the program.

Incremental Programming Process

In
incremental programming, the program is incrementally built using
several iterations. In each iteration of the program, it is compiled
and run to ensure that whatever we have in a given increment is
correct. It is very important to always have a working version of the
program, no matter how much logic we have implemented so far. Here is a
simple algorithm depicting the incremental programming process

Identify the 

main parts of the program
Write the initial stub to include all the parts
Compile and run to verify the correctness
Fix bugs if any
While whole program is not complete
    Change the code to implement more logic
    Compile and run to verify the correctness
    Fix bugs if any
End while
Program complete

As
you could notice in the above process, we always compile and run the
program whenever we add some logic. The idea is to ensure that we write
a clean program all the time. One would think that this is going to
waste time as we compile and run the incomplete program many times.
However this process going to save time rather than waste time in the
long run. The rationale is that, when you write the whole program at
once and try to compile, you would introduce many bugs at once to the
program and it takes more time to debug. The incremental approach on
the other hand cut down time to debug by eliminating bugs along the
way.

An Example

Let’s look at a very simple example
on how to apply incremental programming. The sample problem is to write
a simple billing program for a coffee dispenser utility. The input to
the program from the user would be the number of coffee cups. Given the
number of coffee cups to dispense, the program is required to calculate
the amount and display to the user.

The first step is to come up with the

solution skeleton. The solution consists of main three steps.

get

input
calculate amount
display result

The simplest

skeleton one could write is:

#include < iostream>

using namespace std;

int main()
{
    cout

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