Hi Jean,

Search for "Software Version control ". This has been discussed many times before.

But I have a small remark on this.

CASE 1 :If you are part of a big team that is jointly developing code, then you cannot make do without a solid Version control in place. Such Version controls come along with any professional compiler. If you try to bypass this, what results is utter chaos that cannot be debugged that easily.
CASE 2: If YOU are the only one writing the code and that which will NOT be required to be maintained or corrected by someone else then the following MAY help :

1. Version number is in this form Vxx.yy.mm.dd
xx: Number starting from 1.0
yy.mm.dd : Year-Month-Date

2. When Editing the software and saving it, just remember to comment the changes after changing the version number and let this comment be part of the coding .ANd where possible let this number appear on the display ( LCD, LED, etc) as part of the start up display.

3. Cosmetic and minor bugs - just increment from 1.0 to 1.1.

4. Basic structural or flow changes- increment from 1.x to 2.0.

5. With the Version number + date stamp it will be easy to sort the various versions.

In fact for all the code that I develop ( subject to the conditions as per CASE 2) I follow this. And I am able to easily maintain code developed few years back.

Raghu