Programming in C

D Common Programming Mistakes

D Common Programming Mistakes

THE FOLLOWING LIST SUMMARIZES SOME OFthe more common programming mistakes

made in C.They are not arranged in any particular order. Knowledge of these mistakes

will hopefully help you avoid them in your own programs.

1. Misplacing a semicolon.
   Example
   if ( j == 100 );
   j = 0;

In the previous statements, the value of jwill always be set to 0 due to the

misplaced semicolon after the closing parenthesis. Remember, this semicolon is

syntactically valid (it represents the null statement), and, therefore, no error is pro-

duced by the compiler.This same type of mistake is frequently made in whileand

forloops.

2. Confusing the operator = with the operator ==.
   This mistake is usually made inside an if,while, or dostatement.
   Example
   if ( a = 2 )
   printf ("Your turn.\n");

The preceding statement is perfectly valid and has the effect of assigning 2 to a

and then executing the printfcall.The printffunction will alwaysbe called

because the value of the expression contained in the ifstatement will always be

nonzero. (Its value will be 2.)

3. Omitting prototype declarations.
   Example
   result = squareRoot (2);

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