Applied Engineering Viewmaster 80, Руководство пользователя, Страница: 27 / 37

HOME
- Regardless of whether the Viewmaster 80 is active or inactive,
the HOME command will clear the screen to black and move the
cursor to the upper left corner of the screen. If the HOME command
is issued when the Viewmaster 80 is active and the display mode is
INVERSE, the screen will still clear to a dark display, but subsequent
characters will be inverse.
None of the other expansion-slot 80 column cards support the
HOME command. Because of this, some compatibility problems may
arise with existing BASIC software. This is not a problem unless the
software uses a "Control-L" to clear the screen and home the cursor.
Since the Viewmaster 80 supports both HOME and "Control-L,"
programs can be modified by replacing all instances of HOME with
PRINT CHR$(12). In some cases, as with certain very early DOS 3.3
preboot disks, the HOME command itself must be disabled. This can
easily be done by booting DOS 3.3 and running the following pre-
preboot program:
10 PRINT CHR$(4);"PR#3": PRINT CHR$(12)
20 PRINT CHR$(26); CHRS (49)
30 POKE 1912,0
After running this program, insert the preboot disk and enter PR#6.
The HOME command will now home the cursor, but it will not clear
the screen. To reactivate the HOME command, use the same
program, except POKE a "1" into location 1912.
INVERSE
- Issuing this command from either the immediate or
deferred mode will cause the Viewmaster 80 to switch to inverse text
mode, displaying black characters against a white character block
background, instead of the normal white characters on a black
background. Only output to the screen is inverse; keyboard input is
normal. Using the "Control-Z 3" command has the same effect as
INVERSE, except that the keyboard input is also displayed inversely.
NORMAL
- This command switches the inverse text mode back to the
normal display. The "Control-Z 2" command will cancel the inverse
text mode, but the NORMAL command will not cancel the effect of
the "Control-Z 3" command.
FLASH
- This command is not supported by the Viewmaster 80.
18 ViewMaster 80