In this case, which sentence is more precise ?
1) I'm going out to see the client for a while. If I DON'T come back please switch off my computer.

2) I'm going out to see the client for a while. If I DIDN'T come back please switch off my computer.On top of that, I was thinking to use 'DIDN'T' because the reason is, it could suggest a subjunctive form by imagining ''he wouldn't come back''. Please give me some advice. Thanks.

Question

In this case, which sentence is more precise ?
1) I'm going out to see the client for a while. If I DON'T come back please switch off my computer.

2) I'm going out to see the client for a while. If I DIDN'T come back please switch off my computer.On top of that, I was thinking to use 'DIDN'T' because the reason is, it could suggest a subjunctive form by imagining ''he wouldn't come back''. Please give me some advice. Thanks.

Answer

Hello Mr Hahn,

the first sentence is correct because didn't is past tense and you cannot use it for something that will happen in the future.

Regards, 
airabeth