The APC (Advanced Personal Computer) was a series of business microcomputers released outside of Japan by the NEC Corporation.

[3] The better-known PC-9800 series, released a year later by the different division, had a similar architecture to the original N5200 and used many of the same components.

The most significant differences between the two were that the PC-9801 had slightly lower vertical screen resolution, graphics were standard instead of optional (still using a second μPD7220) and it used 5.25" floppy drives instead of 8".

The position of the N5200 is similar to IBM 3270 PC, but there is significant difference that the N5200 didn't offer the PC-98 compatibility instead it had own software library.

As of 1982, both CP/M-86 and MS-DOS lacked task switching and an ISAM support, so NEC developed a proprietary operating system for the N5200, called PTOS.

Each character cell also had an attribute byte indicating the colour (or, for monochrome screens, whether it was highlighted or not) and any mix of reverse video, blinking, over-bar, under-bar and blanked (not displayed).

(This is higher than the resolution of the user-addressable text screen because graphics can overlay the status line as well.)

C-bus expansion cards (PCBs) could be inserted without removal of the exterior case, as was required for the IBM PC.

Other components didn't even need a screwdriver, except for the outer case, by using robust plastic clips.

[citation needed] As with the IBM PC, the maximum usable memory was 640 KB (the address range of the Intel 8088 and 8086 is 1 MB).

RS-232 serial, Centronics parallel and video interfaces were built onto the motherboard, whereas expansion cards were required for almost every function of an IBM PC except for the CPU, BIOS and built-in RAM.

The base one bit-per-pixel[citation needed] was easily upgradeable to three bits per pixel (taking the graphics mode from monochrome to either eight colours or eight shades of grey).

The computer was capable of running monochrome (or grey) through an NTSC TV monitor, although this was not recommended (text reduced to 40 × 20, graphics to 640 × 200).