Computer instruction in the present tense

[Peggy Thomson <Peggy_Thompson -at- CCMAIL -dot- OSTI -dot- GOV>]

 When you are writing computer instruction, do you write in the
 present tense; for example:


     When you press Restart, the system runs a self-test. If the
     system fails self-test, the processor does not reboot the
     operating system.

 vs future tense:

     When you press Restart, the system will run a self-test. If
     the system fails self-test, the processor will not reboot
     the operating system.


 I have read that such instruction should be written in the
 PRESENT tense. What do you out there in the trenches do, and
 why?