GSX is the standard graphics library for CP/M.
GSX consists of:
GENGRAF.COM - This takes a .COM file and configures it for use with GSX. The resulting .COM file can be run without GENGRAF.COM and launches GSX before running your code.
ASSIGN.SYS - This is a text file which contains the mapping of devices to driver files that implement them.
DDMODE0.PRL - An example of a driver.
GSX.SYS - The device independent part of GSX.
Drivers and ASSIGN.SYS
Vendors provided platform specific drivers which implemented GSX.
Amstrad/Locomotive provided DDMODE0.PRL, DDMODE1.PRL and DDMODE2.PRL which implement drivers for each of the CPC's screen modes.
ASSIGN.SYS is a text file which must exist along side gsx.sys and which contains the mapping of device id to the driver that implements that GSX device. When you program GSX you open a device by it's id.
Example content of ASSIGN.SYS
01 @:DDMODE0.PRL