Learn Turkish: Barkod sisteme girilmedi, paket hâlâ depoda olacak. - The barcode wasn't entered into the system; the package must still be at the warehouse.

This is the main focus of this lesson: using the future tense suffix -AcAk for present logical deductions. Because the barcode wasn't scanned, the speaker is making a strong assumption about the present state of the package. In this context, olacak translates closer to "must be" or "is expected to be" rather than a future action.

Could I say depoda olmalı instead of depoda olacak?

Absolutely. The suffix -mAlI is the standard way to say "must," so depoda olmalı is perfectly correct and means the same thing. Using olacak is just a very common, slightly more conversational way to express that same strong logical expectation.

How is the passive voice built in the word girilmedi?

The verb root is gir- (to enter). To this, we add the passive suffix -il to form giril- (to be entered). Next is the negative suffix -me (not), and finally the definite past tense suffix -di. Put together, girilmedi means "was not entered."

Why does sistem take the dative ending -e (sisteme) instead of the locative -de (sistemde)?