Why does software have bugs?

Why does software have bugs?

Software bugs may occur due to

-Miscommunication or no communication :
1. The exact need / requirements may not be properly communicated.
2. This causes development of software as per the perception of the developers.
-Software Complexity:
1. The complexity of the current software applications are difficult to understand for development team.
2. Multi-tiered architecture, sheer size of various applications, distributed computing etc., contributes to the software complexity growth potential.

-Programming errors:
1. Errors in the programming as per the perception of the developers / team members

-Time Pressures / Deadlines

- Software projects scheduling is difficult.

-Poorly documented code
1. Code modification and maintenance is tough.
2. Badly written or poor documentation causes the code comprehension difficult.