Why does software have bugs?

· Miscommunication or no communication – about the details of what an application should or shouldn't do.

· Programming errors – in some cases the programmers can make mistakes.

· Changing requirements – there are chances of the end-user not understanding the effects of changes, or may understand and request them anyway to redesign, rescheduling of engineers, effects of other projects, work already completed may have to be redone or thrown out.

· Time force - preparation of software projects is difficult at best, often requiring a lot of guesswork. When deadlines are given and the crisis comes, mistakes will be made.