VALIDATION AND ERROR HANDLING. During the development and use of software there are many opportunities for different types of error to creep in. Every programmer should remember the famous acronym GIGO Garbage I n, Garbage O ut.
However carefully you design and code your program, it is very unlikely it will work perfectly first time round. The longer the source code of the programme, the more errors there are likely to be. Good program layout, a modular approach and good use of routines with interfaces and local variables will improve your chances of debugging your program however; we cannot be certain that a large programme will never malfunction. No testing devised so far can prove the program works under all circumstances, the bigger a piece of software, the more likely it is that it may fail sometime. Testing can only reveal the presence of errors. Thorough testing can provide us with some assurance that we have a robust system.