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COMMAS (,) AND COLONS (:)
As suggested before, commas and colons can cause trouble in a file, because they
delimit (end) the data element in which they appear and cause any remaining characters in
the data element to be read into the next Input# variable. (They have the same effect in an
Input statement, causing the common "EXTRA IGNORED" error message.) However,
sometimes we really need a comma or colon within a data element, such as a name written
as "Last, First". The cure is to precede such data elements with a quotation mark. After a
quotation mark, in either an Input or Input# statement, all other characters except a
carriage return or another quotation mark are accepted as part of the current data element.
EXAMPLES:
To force a quotation mark into a data element going to a file, append a CHR$(34) to
the start of the data element. For example:
PRINT#2,CHR$(34)
+
"GUNGA DIN"
or
PRINT#2,CHR$(34);"GUNGA DIN"
If you do this often, some space and time may be saved by previously defining a variable
as equal to CHR$(34) as we did earlier with CHR$(13):
20 QT$=CHR$(34)
400 PRINT#5,QT$
+
NAME$
In each case, the added quotation mark will be stripped out of the data by the Input or
Input# statement, but the comma or colon will remain safely part of the data.
NUMERIC DATA STORAGE ON DISKETTE
Inside the computer, the space occupied by a numeric variable depends only on its
type. Simple numeric variables use 7 bytes (character locations) of memory. Real array
variables use 5 bytes per array element, and integer array elements use 2 bytes each. In
contrast, when a numeric variable or any type is written to a file, the space it occupies
depends entirely on its length, not its type.
Numeric data is written to a file in the form of a string, as if the Str$\) function had
been performed on it. The first character will be a blank space if the number is positive,
and a minus sign (-) if the number is negative. Then comes the number, digit by digit.
The last character is a cursor right character.
This format allows the disk data to be read back into a string or numeric variable
later. It is, however, somewhat wasteful of disk space, and it can be difficult to anticipate
the space required by numbers of unknown length. For this reason, some programs
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