1995 Chevy S-10 transmission problems

I have a 1995 chey s10 blazer the trasmission goes into all the drive gears but will not go into reverse. This happened all at once.I ve never had any problem before this.I always serves ev erything like you should. My question is the trasmission bad or is threr something I can try to do?And is the transmission electrical shift?Any help would be greatly appericated.