* 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.

Running ALTAIR BASIC programs under TARBELL BASIC:

1.  First, since the internal form of ALTAIR BASIC differs drastically
    from the internal form of TARBELL BASIC, and since this is the form
    that ALTAIR BASIC programs are saved onto cassette, these programs
    will not directly load into TARBELL BASIC, even though they may be
    stored on TARBELL cassette format.  There are a few different ways
    to handle this problem.  The simplest, but also the most time-
    consuming, is to retype the whole program into TARBELL BASIC from
    the keyboard.  The second, which requires the use of a paper-tape
    punch and reader, is to punch out the programs to paper tape, then
    read them into TARBELL BASIC from paper tape instead of the keyboard.
    The third, which requires some technical know-how, is to replace the
    ALTAIR BASIC console output routine with the cassette output routine
    provided as part of the I/O section of TARBELL BASIC.  The programs
    could then be read directly into TARBELL BASIC by using LOAD.

2.  The IF statement in ALTAIR BASIC evaluates a variable as true if it
    is not zero.  In TARBELL BASIC, true must be a minus one.

3.  ALTAIR BASIC's CLOAD and CSAVE are replaced by GET, PUT, LOAD, SAVE,
    BGET, BPUT, BLOAD, and BSAVE in TARBELL BASIC.

4.  In TARBELL BASIC, strings must be quoted in a DATA statement.

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