Code Complete by Steve Mcconnell : Chapter 30

The author makes a difference between code modifications done during construction and during maintenance. If the quality of the program degrades after modifications, the program is clearly evolving in the wrong direction.

The author then discusses general guidelines for software evolution:

• Develop more, smaller routines: This increases modularity
• Reduce the number of global variables
• Improve your programming style
• Manage changes
• Review code changes
• Retest

The author then discusses about creating new routines to improve the program. The author then provides ways to reduce complexity of routines:

1. Shorten a routine
2. Reduce nesting
3. Share code