Single and Double Density (Dot Graphics Mode) Your printer usually prints on a single density line, which is 480 dots. However, you can make it print double density, or 960 dots per line. To turn on double density printing, issue the code CHR$(2). To return to single density, the code is CHR$(1). The following program shows how the two forms compare. 10 OPEN 4,4 20 A$=" " :FOR I= 0 TO 127 :A$ =A$+ CHR$(I + 128) :NEXT I 30 : 40 PRINT#4, "DEFAULT AFTER RESET .. . , 50 PRINT#4,CHR$(8);A$;CHR$(15) 60 PRINT#4 70 PRINT#4, "CHR$(2) ... DOUBLE DENSITY : ; 80 PRINT#4,CHR$(2);CHR$(8);A$;CHR$(15) 90 PRINT#4 100 PRINT#4, "CHR$(1) ... SINGLE DENSITY :
; 110 PRINT#4,CHR$(1);CHR$(8);A$;CHR$(15) 120 CLOSE4 Result: DEFAULT AFTER RESET CHR$(2> .•. DOLJBLE DENSITY:~"?®l~"!i:a Quotation Marks If an odd number of quotation marks (CHR$(34)) have been trans- mitted, control characters are made visible. This can be particularly useful when you are making a listing of a BASIC program containing cursor control characters in quotation marks. Advanced Control with the Secondary Address The secondary address is an additional parameter to use with the OPEN command. The secondary address allows you to perform some more advanced control functions, such as setting the number of lines per page or line spacing.
The format of an OPEN command which includes the secondary address parameter is: Where lfn is the logical file number, dn is the device number (also known as as the primary address), and sa is the secondary address. The secondary address position determines the format. OPEN lfn, dn, sa 45