Commodore VIC-20 - Page 119

Chapter 3: Programming the VIC 20 Computer 105
must first calculate the character position of the line where each column is to
begin. This may be illustrated as follows:
Column Number
~
o
JONES, P. J.
BURKE,P. L.
ROBINSON, L.W.
etc.
13
431-25-6277
447-71-7614
231-80-8421
etc.
In the illustration above, columns begin at character positions 0 and 13.
Now, instead
of computing space codes as you go from line to line, following
each column entry you simply insert a TAB function in the PRINT
statement.
Consider one line of the display illustrated above. Counting character
positions, you could display the line without tab stops, as follows:
10 PRINT "JONES,P •. J. 431-25-6277"
Instead of inserting space codes, you could use the space function and
shorten the statement, as follows:
10 PRINT IJONES,P.J.
l
iSPC(3)j"431-25-6277"
But tabbing is easier because you tab to a known column number instead of
counting spaces.
Note that the entries in the third and fourth columns are numbers that
were entered as text. Try rewriting the PRINT statement to display these as
numbers. The numbers no longer align as they did when they were displayed
as characters (in
Chapter 5 we discuss the quirks associated with display
formatting).
In this case, numbers leave a space for a negative sign, and they
do not display zeros occurring after the decimal point. That is why there are
differences.
POS FUNCTION
POS returns the current cursor position. The position is returned as a
number, equal to the column number where the cursor is blinking. Write the
POS function as POS(O).
The following statement demonstrates the capability of POS:
10 PRINT"CURSOR POSITION IS";POS(0)