In 1984, Digital tried to conquer the PC-market with three contestants: the "PDP-8-on-ICs" DecMate-II, the Z80/i8088-based Rainbow, and the PDP-11-based Professional. The idea was to have machines which have the software-support from decades (this was the case with the DecMate-II and the Pro), and CP/M or MSDOS-support on the Rainbow, but it didn't turn out well. IBM's PC won.

The PRO-325 had an RX50 dual floppy drive unit only, the PRO-350 had an RD50/51/52 harddisk too. The 325 and 350 had the F-11 chipset, the 380 was based on the newer J-11, which was developed by Harris Semiconductor. All three had bitmapped display.

The operating system (P/OS - Professional Operating System) was a menu-based version of RSX-11M. RT-11 was also available, as were some third-party OS's, like VENIX, the UNIX variant developed by VenturCom.

The PRO's were also used as the consoles on big VAX systems, like the VAX8550 (the little box on top of the big one is the PRO). They were labeled "VAX Console", but they were normal PRO's (apart from the communication interface to the VAX) running RT-11 or P/OS.