VT55

This document serves as a programming manual for the VT55 terminal, detailing methods and software available for its use, primarily in FORTRAN and BASIC-PLUS languages. Published in February 1977 by Digital Equipment Corporation, it targets new VT55 users, explaining how to leverage the terminal's graphic and alphanumeric capabilities.

The manual introduces fundamental graphic terms and explains the VT55's three operational modes: alphanumeric, graphic, and temporary escape mode, emphasizing how data is interpreted in each. It describes various graphic figures the VT55 can display, including graphs (regular and shaded), markers, and horizontal/vertical lines, and outlines the three-step process for plotting them. Cursor control and mathematical terms like "vectors" are also defined. For larger systems, it covers logical unit numbers, terminal numbers, and event flags for task synchronization.

The core of the manual is dedicated to programming interfaces:

• FORTRAN Programming: It details the single PLOT55 subroutine with 14 different command codes (ICMD 0-13). These commands allow users to attach/detach terminals, select graph numbers, enable/disable graphic figures, plot points and series, draw lines and vectors, place markers, define starting coordinates, position the cursor, erase text, display alphanumeric text, and send escape sequences for various control functions (e.g., screen hold, hard copy).
• BASIC-PLUS Programming: It introduces four specific functions (FNV5, FNV6, FNV7, FNV8) defined in VT55.BAS. FNV5 is the general graphic function, mirroring many PLOT55 capabilities for graphic display and terminal control. FNV6 handles text output, FNV7 provides screen initialization, and FNV8 is for step histograms (bar graphs).

The document also includes appendices that guide users through assembling and linking PLOT55 object files for RT-11, RSX-11, and IAS operating systems, and provide suggested FORTRAN and BASIC-PLUS subroutine examples for creating higher-level graphic applications like grids, coordinate axes, and advanced plotting routines. The overall approach is example-oriented to facilitate learning for programmers of varying experience levels.