Commodore PET User Manual page 119

When you run the program, you will find that it is scrolling up one line, leav-
ing a blank line at the bottom of the screen. This is because PET BASIC gives a
RETURN after printing HIT A KEY to maye
ta
a new line in preparation for the next
print. We can see this by enabling the cursor to blink.
Normally you cannot see the cursor because its blinking is inhibited by the
PET before running a program. However, you can enable the cursor to blink by
adding the following statement to the beginning of the program:
;;::13 PCW:E 548,13 Enable cursor
This is a system location that is discussed further in Chapter 6. Run the pro-
gram with this line added and you will see the cursor blinking at the bottom line.
PHEl~
!
HIT FI KE'T'
M
This program does not really need the cursor, so delete line 80.
To prevent the blank line, add a semicolon ta the PRINT statement in line 90.
We shou Id also add a prompt that RETURN is what is used to exit fram the pra-
gram, Ta incorporate these changes, line 90 should now be edited as follows:
90 .~," H 1 T FI KE'T' OF.: <F.:> TO Et·jD".:
As a final task, you might read over the program and add remarks for any
lines that are not clear. Comment on how the number 920 was devised; you can
optionally put the remark on the same line, using a colon ta separate statements:
120 FOR 1=1 TO 920 REM 920/40=23 LINES
Add a reminder that
:1
is to c1ear the screen; optionally align the remarks:
110 F'F.: 1tH":1" .:
F~Et'1
CLEFlF.: SCREEH
Finally, add a few lines at the beginning of the program to describe it. The final
program BLANKET appears as follows. Save it on tape.
10 REM
~~~~~~~
B LAN K E T
~~~~*~~
20 REM COHTINUOUS-LINE D1SPLAY OF ONE
30 REM CHARACTER ENTERED FROM THE
413 REM KE'T'BOARD
513 REM ~****~~~~**~~~~~~~~~~~~~*******
9';::1 PRIt-H"HIT A 'Œ'T' OR 'CR> TO END".:
113';::1 GET C$: 1 F C$="" GOTO 100
1135 IF C$=CHR$(13) GOTO 170
110
PF~
1NT":1" .: : REM CLEAR SCREEN
120 FOR 1=1 TO 920 :REM 920/40=23 LINES
1:;:0 PRltH C$.:
14';::1 NE>::T
150 F'R 1 NT"
PHEl~'
"
160 GOlO
90
170 END
READ'!',
Figure 3-1. Program
BLANKEl
106