Is it normal to have a probation officer in prison?

Someone I know violated probation for one charge and missed court for another. He had a probation officer that he had been reporting to for a couple of years. The missed court has been counted as time served and he's just been transferred to a different county. He was also just assigned another probation officer. I'm a little confused because I thought you only got probation officers while you're out of jail since you're serving your time on the outside. Can someone clarify what's going on? I'm kind of stupid about this stuff. (This is in TX)