nBackspace, delete, and cancel text
Backspace (CHR$@)) “backs up” the printhead so that you can print two characters right on top of each other. Each time SR- 1O/15 receives a backspace it moves the printhead one char- acter to the left, instead of to the right. You can strike over multiple letters by sending more than one backspace code.
Delete (CHR$( 127)) also “backs up” one character, but then it “erases” the previous character (it’s erased from
Cancel text (CHR$(24)) deletes all the text in the print buffer; that is, in the line before the delete text command. Since SR- 10/l 5 prints one line of text at a time, only that line will be deleted.
The following program shows how these three codes work.
NEW
10 LPRINT "BACKSPACE DOES NOT";
20 LPRINT CHRS(8) CHR$(8) CHR$(8); 3@ LPRINT 'I===WORK"
40 LPRINT "DELETE DOES NOT";
50 LPRINT CHR$(127) CHR$(127) CHR$(127); 60 LPRINT "WORK"
74)LPRINT "CANCEL TEXT";
80 LPRINT CHR$(24);
90 LPRINT "DOES NOT PRINT"
Here is what this program will print:
BACt:::SF’ACE DOES WM WORK
DELETE DOES WORK
DOES NOT F’RINT
The backspace | codes | in line | 20 move the printhead a total of | - | |
three spaces to the left so that the first part of line 30 will overprint |
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the word “NOT”. The delete codes in line 50 “erase” the three |
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letters in the word “NOT” so that it doesn’t even print. |
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In line 80, CHR$(24) deletes the words in line 70. The semicolon |
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at the end of line 70 prevents a line feed from causing that line |
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to print before SR- lo/15 receives the CHR$(24) code. The text |
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in line 90 prints as it normally would because it is after CHR$(24). |
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W “Zero” | printing |
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Sometimes, you want to print “zero” with slash to distinguish |
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between “0” and | “0”. | Your | SR- lO/ 15 can print either “0” or |
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“fY’as you | wish. |
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