# Don't repeat yourself

Referenced in:

DRY (don't repeat yourself). Programs often have blocks of code that are similar. Like input validation, where the same checks are applied to multiple input cells.

Don't copy-and-paste. Instead, make a Sub for the similar code. Use params to specify what the code should do differently each time it is called. E.g., what cell to check, what error message to show.

DRY:

• Helps you be more productive.
• Makes code easier to test and debug, since there is only one copy of potentially broken code.
• Makes it easier to change what the program does. See Make programs easy to change.

The page Reusing code has an example.