Debugging a Program for Syntax Errors and Logical Errors

Debugging a Program for Syntax Errors
As compared to logical errors, syntax errors are much easier to locate and correct because almost all language processor are designed to detect syntax errors automatically.

A single syntax error often cause multiple error messages to be generated by the language processor.

Removal of the syntax error will result in the removal of all associated error messages.

Debugging a Program for Logical Errors
  Logical errors are much more difficult to detect the syntax errors as computer does not produce any error message for such errors.
  
One or more following methods are commonly used to detect the logical errors :
      
Doing hand simulation of the program code :
 One approach is to take the printout of the source code of the program and go through its execution manually with the test data input that produced incorrect results.
       
Putting the print statement in the program code
Another approach is to put several print or write statements at appropriate locations in the program so that the values of different variables can be displayed to indicate intermediate computations results.

  Using a debugger :
    This is the most commonly used approach. Debugger is the software program the assist a programmer in following a program's execution step-by-step allowing him to display intermediate calculation results.
    
Using memory dump :
     This approach is used when the program "hang up" during a test run.