Editing Nascom (section)

==Software==
[[File:Nas sys1 ROMs.jpg|thumb|alt=3,  24-pin 0.6" pitch plastic DIP ICs; 2kx8 mask-programmed ROMs containing the NAS-SYS 1 debug monitor|Mask-programmed 2Kx8 ROMs containing the NAS-SYS 1 debug monitor]]

Initially, users were expected to write their own software. On the earliest machines with limited memory this meant writing Z80 [[assembly language]] on paper, assembling it by hand and then using the monitor program to enter it in [[hexadecimal]] format.

The Nascom 1 provided two 24-pin 0.6"-pitch DIL sockets for ROM memory, each wired to accept a 2708 1 KB device. The first monitor program on the Nascom 1 was named NAS-BUG and was supplied as a single 1 KB 2708 EPROM. This was superseded by NAS-BUG T2. All later versions of the monitor were 2 KB in size and so occupied both ROM sockets. The 2 KB monitors were BBUG (a 1 KB extension that co-existed with T2), T4, NAS-SYS 1 and NAS-SYS 3.

The Nascom 2 provided one 24-pin 0.6"-pitch DIL socket for ROM memory (other sockets on the Nascom 2 board could also be configured to accommodate ROMs), wired to accept a 5V 2716 2 KB device. Nascom 2 kits were initially provided with NAS-SYS 1 in masked ROM (the photo shows that at least two date-codes exist for these ROMs). NAS-SYS 1 was the only Nascom monitor ROM to be supplied as masked ROM; all other versions were supplied as EPROMs.

All of the debug monitors provided similar capabilities, with different levels of sophistication:

* Examine and modify memory
* Start program execution from a specified address
* Insert a breakpoint (in RAM only)
* Single-step (through ROM or RAM) and display registers. Hardware support was provided for this, using the Z80 non-maskable interrupt
* Save a memory region to/load a memory region from [[cassette tape]]

As the user-base grew, user-group magazines published [[type-in programs]] either in [[assembly language]] or as [[hexadecimal]] dumps or (later) in [[BASIC]]. Computing magazines such as [[Personal Computer World]], [[Practical Computing]] and [[Computing Today]] published articles and software specifically for the Nascom computers.

Later, commercial software was made available either on cassette tape or programmed into one or more EPROMs (usually 1 KB 2708 devices).

When disk drives became available, various disk operating systems became available, including PolyDos (developed by [[Anders Hejlsberg]] and inspired by the software of the [[PolyMorphic Systems]] [[Poly-88]]), NAS-DOS and [[CP/M]].

The predecessor of [[Borland]]'s very successful [[Turbo Pascal]] [[compiler]] and [[integrated development environment]] (IDE) for CP/M and DOS was developed by Anders Hejlsberg of Blue Label Software for the Nascom 2, under the name ''Blue Label Software Pascal'', or ''BLS Pascal''.

In 1979 the Nascom 2 came with an onboard ROM with early Microsoft Basic 8 KB interpreter.