Q:

Difference between た／ている／plain form + とき

I don't really understand the difference between た／ている／plain form + とき. I want to understand this form so, if you can give me a lot of examples and explanations, I'll be grateful !
Thanks !!

A:

The only differences between these three are the tense of the verb. Attaching 〜時{とき} holds the same function in all three cases.

〜た：past tense

行ったとき。。。When (I) went...
勉強したとき。。。When (I) studied...

〜ている： present progressive (continuous) tense

行っているとき、。。。When (I) am going...
勉強しているとき。。。When (I) am studying...

plain form：

行くとき、。。。When (I) go...
勉強するとき。。。When (I) study...

