First of all, I've read this subject and want you to read it because its importance.

An error in a program is called a bug. Bugs my be one of the following:

SYNTAX ERRORS
A syntax error: occurs when a language is not used correctly. A compiler or interpreter will not able to translate with syntax errors because they don't make sense Syntax errors usually occur because:
1- The programmer has misunderstood the rules of the language; or
2- A transcription error has been made. A transcription error is a mistake made in writing or keying.

An example of syntax errors in BASIC
1- 300 LET A =2(O+3)
This should read '300 LET A=2*(O+3)' The programmer probably didn't realize that an asterisk was needed.

LOGICAL ERRORS
A logical error occurs when the program designer or the programmer makes a mistake in working out the sequence of instruction required to produce a particular result.

An example of logical errors
1- The following BASIC program module is intended to print INCORRECT MONTH
Whenever the value of MONTH is not between 1 and 12, inclusive.