The DEC PDP-1 was the first ever minicomputer, and the first ever computer with hard disc storage space (about 150 KB).
Constructed entirely of solid-state circuitry, the default equipment took 17 square feet of storage space, and cost $120,000. However, at the time this was cheap, and good value considering the advances made. Purchased mainly by universities. Came with a tape reader/writer for larger programs. Control panel used small switches to program in real time onto the hard disc.
Add-on was a large Cathode Ray Display, with 512*512 circular b/w raster.
The DEC PDP-1 was the first computer to have a hardware add-on which was also the first sound hardware add-on (four digitally switched flip-flops). And the first to have compressed music (the data formate was optimized to store baroque music).