Commodore VIC-20 - BASIC Commands

There must be NO SPACE between the quotes in this line, to
indicate an empty value. When the person is not typing anything,
the empty value goes into the string variable (in this case
represented by AS and the IF statement sends the program back to
the GET statement. This loop repeats indefinitely, until the person
operating the computer hits any key on the keyboard. At this point,
the program continues with the line following line 10.
Add this line to the program:
100 PRINT AS; : GOTO 10
Now RU N the program. No cursor appears on the screen, but any
character you type will be printed on the screen. This includes all
special functions, like cursor and color controls and clearing the
screen. This two-line program can be developed into a screen
editor, shown below.
There are many features that you could use in a screen editor. A
flashing cursor is nice to have, and can be programmed. Also, you
may wish to "trap certain keys, ke |jfflj , so as not to i
erase the screen accidentally. Or you may wish to program the
function keys for whole words. The following lines give each
function key a special purpose. Remember, this is only the
beginning of a program that you can customize for your needs, like
word processing or data capture. ,
20 IF AS - CHRS(133) THEN POKE 36879.8: GOTO 10
30 IF AS - CHR$(134) THEN POKE 36879,27: GOTO 10
40 IF A$ - CHR$(135) THEN AS="DEAR SIR:" + ,
CHRS(13)
50 IF AS = CHR$(136) THEN AS = "SINCERELY," +
CHRS(13)
The CHRS numbers In the parentheses come from the CHRS
code chart in the Appendix, which lists a different number for each
key character. The four function keys are activated here to perform
the tasks represented by the instructions which immediately follow
the word THEN in each line ... of course you could designate
different keys by changing the CHRS number in parentheses, and
different instructions after the THEN statement.
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