GL contains a number of subroutines that perform startup functions or reconfigure the system to accommodate a requested mode of operation. For example, the overlay, underlay, doublebuffer, singlebuffer, multimap, onemap, RGBmode, and cmode subroutines do not take effect until the gconfig subroutine is called.
Other subroutines initialize or terminate programs (ginit and gexit); clear the viewport, color bitplanes, and z-buffer (clear, zclear, and czclear); or turn on or off full-screen mode (fullscrn and endfullscrn). The greset subroutine resets all global state attributes to initial values. The gbegin subroutine initializes the graphics system without changing the color map. The gversion subroutine returns the version of GL being used. The getgdesc subroutine returns information about the currently installed graphics hardware.
GL runs on top of Enhanced X-Windows and initializes with a default font. GL also has access to X fonts through the X server.
| clear | |
| Clears to the screenmask. | |
| czclear | |
| Clears the color bitplanes and the z-buffer simultaneously. | |
| endfullscrn | |
| Ends full screen mode. | |
| fullscrn | |
| Enables drawing outside current window boundaries. | |
| gbegin | |
| Initializes the graphics system without changing the color map. | |
| gconfig | |
| Reconfigures the system. | |
| gexit | |
| Terminates a graphics program. | |
| ginit | |
| Initializes the graphics system. | |
| greset | |
| Resets all global state attributes to initial values. | |
| gversion | |
| Returns the version of GL being used. | |
| zclear | |
| Initializes the z-buffer. | |