TOS provides two software interfaces to its graphics routines: VDI and Line A. This document describes the "Line A” interface to the ST’s low-level graphics primitives, as provided in all ST computers with TOS in ROM. It assumes you are familiar with the ST’s operating system and
68000 assembly language.
While VDI is appropriate for many applications, it is sometimes advantageous to give up some convenience for speed and additional features, like support for all 16 Bit Bit logic operations in TextBit. Line A provides an interface for simple graphics operations, with these additional features.