Is there a word or expression for improving software

I am writing a text and I have to say what skills I developed during my internship. What do you call improving software? Software improvement? I feel like there would be a better word or expression for this.

EDIT: By improving, I mean that I added features to the software that were requested by the company.

Solution 1:

If you're trying to avoid overstating your contributions because you feel terms like "upgrade" may imply you completely overhauled the software, you might say that you made enhancements to or extended the software.

Solution 2:

Perhaps "refactoring" the code would fit your need?

refactoring - Improving a computer program by reorganising its internal structure without altering its external behaviour.

Or you "extended" the program. The definition fitting this usage is...

extend - to increase the scope, meaning, or application of

Solution 3:

If you are making it better by adding onto it upgrade would be an apt description

Upgrade-
2. an increase or improvement
3. a new version, improved model, etc.
4.an increase or improvement in one's service, accommodations, privileges, or the like
5. something, as a piece of equipment, that serves to improve or enhance

Upgrade- Raise (something) to a higher standard, in particular improve (equipment or machinery) by adding or replacing components

To a lesser extent ameliorate- to make or become better, more bearable, or more satisfactory; improve