What is an error in programming?

Finally you will run the object file to obtain the output. You will probably produce a program listing which is a printout or soft copy of the source program instructions as a reference while working and coding the program.

When the computer is interpreting or compiling a program that is your source code, an error, whether major or minor will cause it to either produce (output) results or not reach the stage of output at all. There are different types of errors which will cause your program to ‘crash’. We will be looking at some of these errors:

v Logic errors

Logic errors occur when the programmer makes mistakes in the sequence of the program statements such using the wrong formula or function ( ie using a MOD instead of SQR FUNCTION). The program will usually compile that the compiler converts the source code to object code. NOTE: that compilation with logic errors does not generate any syntax errors or any warning messages but when the program is run it produces the wrong results.

v Syntax errors

Syntax errors occur when a mistake is made in the programming language rules or violating the rules governing the structure of the language.  In short a syntax error occurs when the programmer fails to follow the rules of the programming language exactly. For example if a keyword such as input or print is spelt incorrectly or an endif was left out.

v Run-time errors or execution errors

Run-time errors occur as the program compiles or runs. These errors are usually due to unexpected events such as division by zero or lack of memory for the computer to manipulate the data or a loop with no end. Run-time errors can be very difficult to trace as the program may produce results most of the time.

Example: for x = 1 to 3

    Result = result/(average-1) when average is equal to 1 you will be dividing by zero, this cause the computer to hang-up or an error message will be produced.

v Debugging

Debugging is the process of finding errors in the source code (detection), understanding why they occurred (diagnosis) and correcting them. Errors are found through error messages generated by the program or the operating system or because the program does not behave as expected.

TESTING ALGORITHMS

Desk checking or dry running is the process of checking an algorithm for errors. You do this by pretending to be a computer and executing the steps in the algorithm one by one, while keeping a record or track of the results.

Trace table is a very useful tool which allows you to see the state of your algorithm with as much details as you wish. Each row of the table shows the state of one step in the algorithm and each column shows the value of a variable at that step. The trace table allows you to check the algorithm for errors. For example:

Complete the trace table for the following algorithm, given that the number 4 is the input value for X

Read X

 FOR M = 1 TO X DO

Y = X-M

Z = 5*Y- M

END.

PRINT Z

X         M         Y         Z

4

4

4

4

Testing

As you complete your program, you must ensure that it works for any correct input data that the user gives it. The testing phase is to detect errors or problems in the program.

Test data: the values that are used to test or check the correctness of the program. The test data should include a wide range of sample data including extreme values and inputs that are not valid.

Structured walk through: This is the process of performing a manual trace on the program to detect any possible errors.

Executing the program

If you have translated the program to its object code without errors, you can now execute the program and see the results. The final two terms commonly used with program execution are:

Anyone involved in computer programming, even (perhaps especially) beginners are going to encounter errors and bugs of various types that force them to hunt down that culprit bit of code and make the necessary adjustments.

It can be bewildering and stressful when an unexplained error crops up and stops you in your tracks. But being aware of the basic types of errors that can occur will at least give you a “fighting chance.” If you want to avoid programming errors in your coding assignments, pay experts from AssignmentCore who will handle your “do my programming homework” request online.

Here are the three main classes of computer coding errors you’re likely to run into:

1. Logical Errors

We will divide our errors into three classes: logical, syntax, and semantic. But be aware that these same classes can be either static (compile-time) or dynamic (run-time) in nature.

Logical errors are the hardest of all error types to detect. They do not cause the program to crash or simply not work at all, they cause it to “misbehave” in some way, rendering wrong output of some kind. One example of a logic error is null reference. Null reference errors are responsible for a huge chunk of application bugs, and they are usually very simple mistakes involving missing or wrong “computer logic.” It may be a property/field is null, a condition has prevented an object from being created, or a local variable field is declared but not initialized.

Logical errors “make sense” as to the computer language itself, but they simply don’t fit into the program correctly.

2. Syntax Errors

Syntax errors in computer programming differ from logical errors in that they don’t follow a correct sequence in the computer language.

With compiled languages, you will run into any syntax errors at compile time, and they will have to be corrected before the program can run. For interpreted languages, a syntax error would pop up during run time, and your error message might not even specify it’s a syntax problem. However, in both cases, the compiler/interpreter will give you the location of the syntax error, which makes it rather easy to find/fix.

In general, syntax errors are smaller, even single-digit, errors; while logic errors can involve larger sections of code and the general flow of the code. Some examples of syntax errors would be: missing semicolons at a line’s end and an extra/missing bracket at end of a function.

3. Semantic Errors

Semantic errors are improper uses of “program statements.” Though different definitions of semantic error exist, we are saying here that logic errors produce wrong data while semantic errors produce nothing meaningful at all.

Thus, to sum up the differences between these three classes of errors, we can say:

• Semantic errors have to do with meaning/context. It’s like using the wrong word in the wrong place in a human language sentence. A computer language example would be confusing a metric with an imperial input value.
• Syntax errors are like “spelling and grammar” problems. They often stem from typos where parentheses or single characters are input incorrectly.
• Logic errors have to due with program flow. If you get a wrong operation or a misordered operation, it’s probably a logical error. Use of a wrong conditional operator or null reference errors are good examples.

Of course, it is easy to avoid these errors with the help of highly experienced quality assurance and testing professionals, and the time saved and errors fixed will be well worth the cost.

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