6 Developing an application program
The process of developing any software starts with an analysis of the task or tasks to be performed by the computer, an analysis designed to tease out how the computer is to behave under every possible circumstance. The software development process may continue through the drawing of flowcharts like the ones you have seen, or the software developers may prefer other means of arriving at an understanding of each individual element of the task and how these elements fit together. In either case, however, the next step will be to write the computer program. This will take the various elements of the task and convert them into a program by use of a programming language, which is a structured language with a limited set of words and symbols and which can be used to tell a computer how to perform a task. Finally, the program must be ‘debugged’ (made free of errors) through extensive testing, and also documented to facilitate any future work on it.
After this there may be more forms of testing, from user evaluation of the ‘user experience’ of using the software to the more dramatic, literally pulling the plug on the computer part way through executing the program to see ensure the program fails gracefully. Important if your program if your program is running a bank’s teller machine and fails part way through a user withdrawing money; potentially vital if your program is monitoring a safety critical system.
There may be yet more steps before your program can be used, such as user training in complicated applications. The computer hardware and its programs are just the first steps towards delivering an effective system.
Before you finish this session, you are going to take a short look at a special form of application programming: programming for the web.