1989 Cadillac Deville

While driving to work one morning all my instramentation lights went out including my heater and turn signals. That evening I was driving home and stopped for gas, and when I tried to restart my car the battery was dead. The battery is brand new and has had no problems. I thought the problem at the time may be a blown fuse until I found the battery went dead. Could this be the alternator and maybee the light going out was a way the computer was trying to conserve energy?