Printer SPOOLER

The British company M.M.L. Systems Ltd. distributed at the end of the eighties a spooler1 , find the original manual here.

As known CP/M is an operating system not using interrupts for I/O. If, for example, a key is pressed the corresponding character will be available. But if the character will not be read before the next key pressure it will be lost. Also quitting a program (usually typing Ctrl-C) must be performed by software. This applies also for printer jobs. If such a job is running no other action may take place.
Exactly that is the starting point of this RSX. Data sent to the printer will be first written into a file. This is very fast using a RAM-disc. The RSX controls the following system calls and whenever there is an access to the console character input routine and no character is available, the RSX reads a character from the file and sends it to the printer. From the users point of view this looks like multi tasking.

Here the source files:

♦	Main program	The program installes the RSX
♦	RSX	The RSX must be combined with the main program
♦	Deleting program	This tool deactivates the RSX

1.	Later I found another Spooler in a Dutch CP/M User Group (No. 864)