Radio Shack TRS-80 Model 100 Basic Manual page 18

A new line can be added to a BASIC program at any time simply by typing it with the
appropriate line number. If you want to add a statement before line 10, give it a
number less than 10 (the smallest line number allowed is 1). If you want to add a line
between the two lines, give it a number between 10 and 20 (e.g., 15).
Line numbers 10 and 20 were used to allow insertion of new lines. If successive line
numbers had been used, for example 15 and 16, then no new lines could have been
inserted.
It
is a good practice to use line numbers that are multiples of 10 (or at least
5).
Here's your program again:
10 PRINT "HOW"
j
"NOW"
j
20 PRINT "BROWN
II
j
"COW"
Suppose you want to insert a line between 10 and 20. Simply type:
15 PRINT "SPLENDID ";
~
When you list the program now, it will show:
PRINT "HOW"; "NOW";
PRINT "SPL.ENDID
"i
PRINT "BROWN
!I;
"COW"
Even though line 15 was typed after lines 10 and 20, it takes its correct place in the
program because its line number falls between 10 and 20.
Execute this program. The following output will result:
NOW SPL.ENDID BROWN COW
It should be clear by now that any BASIC program can be edited easily with the use
of the line numbers. You can add, delete, insert, and change lines and that is all you
ever need to do.
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