what is a bug..

when software is not behaving properly as per the requirement we can call there is  a bug .A software bug occurs when one or more of the following five rules is true:

1. The software doesn't do something that the product specification says it should do.
2. The software does something that the product specification says it shouldn't do.
3. The software does something that the product specification doesn't mention.
4. The software doesn't do something that the product specification doesn't mention but should.
5. 
   
   
   
   The software is difficult to understand, hard to use, slow, orin the software tester's eyeswill be viewed by the end user as just plain not right.

    Bugs are caused beacuse of numerous reasons such as coding error ,design error ,specification .

   
   

   
   

   COST OF BUG:when a bug found at design stage it costs less to fixed,but when the same not found till the coded and tested phase it cost so high if that bug detected by the customer it cost a million dollar.