Commodore Computer Commodore 64 Uživatelský manuál stáhnout pdf (Strana 37)

Creating a Relative File

When a relative file is first to be used, the OPEN statement will create that

file;after that, that samefilewillbe used.The replaceoption (withthe@)sign)

does not erase and re-create the file. The file can be expanded, read, and written

into.

FORMATFORTHE OPENSTATEMENTTOCREATERELATIVE FILE:

OPEN

file#, device#, channel#, "name,L," + CHR$(record length)

EXAMPLES OF OPEN STATEMENT CREATING RELATIVE FILES:

OPEN2, 8,2, "FILE,L,"+CHR$(lOO)

OPEN F, 8, F, A$+ ",L,"+ CHR$(Q)

OPEN A, B,C, "TEST,L,"+ CHR$(33)

Record Length

Table 7.1 RELATIVE FILE FORMAT

DATA BLOCK

BYTE DEFINITION

0,1

Trackand

sectorof next datablock.

2-256

254 bytes of data. Empty records contain FF (all binary ones)

in the first byte followed by 00 (binary all zeros) to the end of

the record. Partially filled records are padded with nulls (00).

SIDE SECTORBLOCK

BYTE DEFINITION

0,1

Trackand sector of next side sector block.

Side sector number. (0-5)

Record length.

4,5

Track and sector of first side sector (number 0)

6,7 Track and sector of second side sector (number 1)

8,9

Track and sector of third side sector (number 2)

10,11 Track and sector of fourth side sector (number 3)

12,13 Track and sector of fifth side sector (number 4)

14,15

Trackandsector of sicth side sector (number 5)

16-256

Trackand

sectorpointersto 120datablocks.

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 64 65

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Commodore Computer Commodore 64 Uživatelský manuál Strana 37