If you are using an HP 9816, 9836, or other HP computer with separate alpha and graphics hardware, some of the differences you find in HTBasic will be the same differences you would find moving to an HP 310 or another HP computer with a fully bit-mapped alpha/graphics display. Bit-mapped displays are driven by the CRTB Mode Driver. A CRTB display has only bit-mapped images. The ALPHA image is written into one or more of the graphic planes. One plane can be separated from the others for use solely for the ALPHA image. Or, all the planes can be merged for shared use between ALPHA and GRAPHICS. See SEPARATE and MERGE ALPHA in the Reference Manual.
When ALPHA and GRAPHICS are merged, ALPHA text is converted to graphic bits and written into the graphic planes, overwriting any graphics data that might be present. Therefore, ALPHA and GRAPHICS cannot be dumped separately. And when the ALPHA text is scrolled, any graphic data present will be scrolled also. This is the default mode for a CRTB display.
The SEPARATE ALPHA statement can be used to simulate 9836C displays with independent ALPHA and GRAPHICS screens. Either image can be turned on or off or DUMPed independently of the other.
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