The information here is incomplete. Aside from the Wedge which was sold by a third party, NEC itself sold a number of addon units. The 32k RAM keyboard-shaped PC-8001A was the main micro computer, with everything built into the keyboard case $ a design similar to the Commodore 64 or he Atari 400 or 800 or Atari ST. But NEC also made and sold the PC-8031A mini disk unit, which allowed up to four half-height floppy disc drives to be installed. These were DSDD drives with 360K capacity each, so by installing 4, you got an instant storage capacity of up to 1.44 megs on drives A: and B: and C: and D:. The PC-8031A was an external beige box in which you could install the floppy drives. It had a built-in floppy drive controller and connected to the keyboard computer by a cable.
Then there was the PC-8012A I/O unit. This contained serial and parallel ports as well as a primitive analog sound I/O similar to the creative sound blaster. Again, this was a beige box that also connected to the main keyboard computer through a cable, or it could connect to the 8031A floppy drive unit via a pass-through port.
Finally, NEC sold the JC-1202DH(A) color character display, which uew the exact same chassis and cabinet and power supply as the earlier NEC green screen monochrome monitor but with color circuity. It was a simple analog monitor, no different from the Commodore or Apple color monitors. You could use any analog color monitor with this computer. As with the C64 or the Apple $$+, the color monitors were interchangeable.
NEC also sold its own particular brand of dot matrix printer with this computer. It used a standard Centronics (today we call it a parallel) port. You had to have the 8031A drive unit to load drivers for the NEC printer and run the software. I''m not sure whether the I/O unit came with an extra 32K of RAM on a board inside the beige box, but I think so. If memory serves, this thing ran Wordstar and the NEC printer was EPSON-compatible, so you could use EPSON printer drivers and output the usual graphics + text using escape and control characters to produce primitive block graphics.
This unit was very impressive for its time. It cost a lot for all 3 units $ you stacked the two beige boxes up on top of one another and put the NEC monitor on top of those, then hooked them up via cable to the keyboard computer and hung the dot matrix printer (and a Hayes serial modem if you wanted) off the back of the I/O module. But if you paid the money and set it all up, you had a very fully functional machine that could connect to a BBS at 300 baud, print out properly formatted documented using standard dot matrix graphics + text, play 8-bit sounds, and you had many of the same capabilities of the later EGA monitors with a variety of different colors. The disk drives were particularly good. They didn''t go bad, unlike the full-height Tandon drives on earlier computers like the Kaypro II or the TRS-80. Those full-height 48 TPI Tandons used in earlier computers were notorious for drifting out of alignment, but the 96 TPI DSDD NEC floppy drives never went bad. If you find one of these units with the floppy drive module in storage and fire it up, chances are it will still boot and work.