CREATE - Write an entry in the table of contents

Syntax:

CALL 4026H
Input:

  • filename in FNAM (IY+1)

  • File Type in TYPE (IY+9)

  • The allocation map must be loaded (MAPAREA).

  • The drive must be powered on.

Exit:

The file was entered in the table of contents, the first data sector for this file was reserved.

Registers used:

AF, BC. DE, HL

Error handling:

  • A = 0 Entry made

  • A = 2 File already exists

  • A = 3 no space in the table of contents

  • A = 7 no free sector (disk full)

  • A = 9 An address mark was not found

  • A =10 A checksum error occurred during reading

  • A =17 BREAK key pressed

An entry is made in the directory for the file specified in FNAM and the first free sector is reserved for this file.

First, SEARCH checks whether a file with the same name already exists. If not, a free entry in the table of contents is determined with FIND and a first free sector is searched for with MAP. If both were successful, the entry is made in the table of contents.

To do this, the file type, separator ‘:’, file name and the address of the first sector are entered in the 16-byte entry found in the table of contents, and the table of contents is written back.

The allocation map should then also be written back to the diskette, otherwise the first sector will not be definitively assigned. If you forget this, it will later lead to a double allocation of this sector and possibly to an inextricable mess of the data.

Of course, rascals can take advantage of this and make two different entries for the same file with different names in the table of contents. Sensible ???

Before calling CREATE, you should definitely check the write protection of the diskette.

The success of the action can be checked by evaluating the A register.

Example:

...
DI                      ; disable interrupts
LD (IY+11),10H          ; select Drive 1
CALL 4008H              ; and turn on
LD BC,50                ; 50 ms delay
CALL 4038H
IN A,(13H)              ; check write protection
OR A
LD A,4
JP M,400EH              ; read only!
CALL 4011H              ; load allocation map
LD HL,DNAM              ; filenames in the field
CALL 401DH              ; copy to FNAM
LD (IY+9),'B'           ; set Type = 'B'
CALL 4026H              ; enter the file in the table of contents
OR A                    ; error occured?
JP NZ,400EH             ; yes, to the ERROR routine
CALL 4017H              ; write back allocation map
CALL 400BH              ; turn off the drive
EI                      ; allow interrupts again
...
DNAM: DEFM '“KARTEI”:'

An entry is made in the table of contents of the diskette in drive 1 for the binary file “KARTEI” (type = B).

Internally called routines: SEARCH, FIND, MAP, READ, WRITE