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TBASIC.2
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1984-04-29
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* Line Descriptors:
In TARBELL BASIC, line descriptors may not only be line
numbers, as in conventional BASIC'S, but also may be any
alphanumeric string of characters (including numbers),
except spaces or punctuation. If the descriptor is in a
statement that is referencing another statement, it may
have an offset appended. The offset is indicated by the
symbol "+" or "-". This feature may be used to greatly
increase readability, and thus increase maintainability of
programs.
Line descriptors need only be used on lines which are referred
to by another statement, such as a GOTO, GOSUB, GOPROC, RESTORE,
etc. Line descriptors are used in a similar fashion to the
labels in assembly language. A line descriptor may be a number,
just as in normal BASIC's, but need not be in any order. Line
descriptors usually are chosen with names that mean something
in the program, so that it will be easy for the programmer to
remember the name of a particular line or subroutine.
See Appendix G for more examples of the use of line descriptors.
Examples:
SORT A=B+6 "SORT" is the descriptor, in this case, the
name of the statement.
GOTO SORT+1 "SORT+1" is the descriptor, indicating a
transfer to the statement following "SORT". That
statement may or may not have a name of it's own.
GOSUB SORT - 5 "SORT - 5" is the descriptor, indicating a transfer
subroutine call to the statement 5 lines before
the statement named "SORT".
10 FOR N=1 TO 5 Line numbers can still be used, but need
05 PRINT N,SQR(N) not be in order, and are not used to
20 NEXT N edit in the same manner as other BASIC's.
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