Types of programming error
Programming errors
When a programmer writes a program, errors are sometimes made in the code. Finding errors, or ‘bugs’, in a program is known as ‘debugging’ a program. Errors can be classified under the three headings.
- Syntax errors.
- Logical errors.
- Run-time errors.
These classifications come about because the first type of error should be picked up by your translator's diagnostics. In other words, when you try to translate your program from source code to object code. The second type of error can be translated successfully and won't actually cause your computer to display an error at all. It's up to the programmer to find these. The third type of error again can be translated but this time will throw up an error when the object code is run.
1. Syntax errors
Every program has its own set of rules regarding the instructions that can be used and the way that each instruction must be constructed. If a programmer were to break one of those rules, the program would not be translatable into object code. For example, look at the following Python program:
Print(“Hello world”)
If we tried to translate this program into object code, our translator program would diagnose a syntax error because the rules of Python haven't been strictly followed. The keyword Print starts with a capital letter. Python’s keywords are case sensitive. Print should have started with a small letter p.
2. Logical errors
When a programmer has written a program that contains logical errors, it can be translated and run. However, the program will produce incorrect results or displays. For example, suppose you had a program line that multiplied two numbers:
Result = valueA + valueB
This would be translated into object code correctly. When the executable code is run, however, it would produce an incorrect result. This is because the + was used instead of the multiplication symbol. It is up to the programmer to discover these types of bugs by writing a very good test plan to pick them up. If the test plan isn't comprehensive, then the programmer will think that they have written a good program but it will be flawed!
3. Run-time errors and arithmetic errors
As with logical errors, a program with these types of errors can be translated without an error being discovered. Unlike logical errors, however, the program will stop running and a run-time error will be displayed. A typical example of a run-time error is when a division by zero occurs in a calculation. Dividing by zero is a meaningless calculation. Impossible arithmetic operations that result in errors are also called arithmetic errors. Another run-time error would occur when a program has run out of memory. There is a fixed amount of RAM in any computer. Some of it will be used for the operating system and the rest will be used for applications and data files currently needed by the CPU. If the CPU can’t run a program because there is not enough memory available to store temporary values, for example, then it will display a run-time error message and stop working.