Different between 'effect' and 'impact'

Solution 1:

Impact and effect can be used to mean more or less the same thing, but in context they usually do not mean the same.

Actually, if you change has no effect on the system, I would not want you to spend time on it. At the very least, I would hope your change would have an effect: the issue should be fixed!

As for impact, in this case, it refers to a larger-scale, usually negative "effect". In software development, and effect to the system would normally refer to a functional change in how the user perceives the system, whereas the impact of a change could mean several things:

• The actual amount of work that needs to be done for the change: our impact analysis shows we need to change over 100 classes to implement this change.
• The proportional part of the system in which the (desired) effect is observable: this small change will have a huge impact on the overall user experience throughout the system.
• The proportional size of the effect of the change: the performance impact is enormous, the system will grind to a halt!

In these case, I would not use effect. I would use that to describe the functional changes:

• Even if we change all 100 classes, the only effect will be that users see a different typeface on the OK-buttons.
• _This is a quick win: we make a small (low impact!) change in one place, and the effect is overwhelming: every user can now select their own personal skin for the application!_
• This database change is unnecessary; even worse, the effect will be a very slow system for our users.

A software developer myself, when I am confident a change should be made, I will always try to present a large effect and a small impact!