## Alpha Mode Display

This is the “standard” operational mode. It is used to display alphanumeric characters and semigraphic box graphics, and simulates the operation of a typical computer terminal with functions for scrolling, cursor positioning, clear screen, line delete, etc.

Each 8-bit character is assumed to be an ASCII character and is displayed if its high order bit (sign bit) is cleared. Lower case letters are displayed in reverse video. If the high order bit of the character is set it is assumed to be a “Semigraphic 6” graphics box. See the computer manual for an explanation of semigraphics functions.

Table B.1. Alpha Mode Command Codes

Control Code | Name/Function
--- | ---
01 | HOME - return cursor to upper left hand corner of screen
02 | CURSOR XY - move cursor to character X of line Y. The binary value minus 32 of the two characters following the control character are used as the X and Y coordinates. For example, to position the cursor at character 5 of line 10, you must give X=37 and Y42
03 | ERASE LINE - erases all characters on the cursor's line.
06 | CURSOR RIGHT - move cursor right one character position
08 | CURSOR LEFT - move cursor left one character position
09 | CURSOR UP - move cursor up one line
10 | CURSOR DOWN (linefeed) move cursor down one line
12 | CLEAR SCREEN - erase entire screen and home cursor
13 | RETURN - return cursor to leftmost character of line
14 | DISPLAY ALPHA - switch screen from graphic mode to alpha numeric mode