The HP 9836C display is driven by CRTA Mode drivers. A CRTA display has distinct ALPHA and GRAPHICS images. Either the ALPHA or GRAPHICS images can be displayed, or both can be displayed at once, overlapping each other. The hardware for the two images is independent. HTBasic does not directly emulate CRTA Mode. HTBasic does not support CRTA mode. Use the SEPARATE ALPHA command for the best 9836C emulation.
