Atari 400

14B User's Handbook to the Atari 400/ 800 Computers
Keyboard
The OPEN statement for the keyboard can be for input only .
When the keyboard is used for input, the question mark does
not appear as a prompt for an INPUT statement. Also, the
response to
an I N PUT statement does not appear on the display.
The third argument of an OPEN statement for the keyboard is
ignored.
EXAMPLE
10 DIM A$(1)
20 OPEN #2, 4, 0, "K :"
30 GRAPHICS 3 + 16
40 INPUT #2, A$
50 PRINT
60 END
The previous
example contains a program that maintains a
graphics
display until input is received from the keyboard. Line
10 dimensions the string variable A$. Line 20 opens the keyboard
for input. Line 30 selects graphics mode 19, which is the same as
graphics mode 3, but without a text window.
In order to maintain a full screen graphics display, the program
must pause,
but not end. When a character is displayed, the
display returns to graphics mode O.
When the INPUT statement is executed at line 40, the program
waits
for input, but does not ruin the display by printing the
prompt (?) or the response. As a result, the display is preserved
until the operator enters a suitable input for A$. The easiest
response to the INPUT statement is the Return key.
Disk
An 1/ 0 channel can be opened for a disk for any of the 1/ 0
operations listed in Tab le 5-1. When an OPEN statement for the
disk
is executed, DOS must have been booted and ready to
operate.
An
OPEN statement for a disk file must inlcude the filename and