ASCII, 01-09-94
3.20 DELETE FILE [FCB] (13H)
Parameters: C = 13H (_FDEL)
DE = Pointer to unopened FCB
Results: L=A = 0FFH if no files deleted
= 0 if files deleted OK
All files in the current directory of the disk specified by the FCB, and
which match the ambiguous filename in the FCB, are deleted. Sub-directories,
system files, hidden files and read only files are not deleted. If any files
at all are successfully deleted then this function returns with A=0. A return
with A=FFh indicates that no files were deleted.
3.21 SEQUENTIAL READ [FCB] (14H)
Parameters: C = 14H (_RDSEQ)
DE = Pointer to opened FCB
Results: L=A = 01H if error (end of file)
= 0 if read was successful
This function reads the next sequential 128 byte record from the file into
the current disk transfer address. The record is defined by the current
extent (high and low bytes) and the current record. After successfully
reading the record, this function increments the current record and if it
reaches 080h, sets it back to zero and increments the extent number. The
record count field is also kept updated when necessary.
Unlike CP/M it is possible to have partially filled records, since the
file size is not necessarily a multiple of 128 bytes. If this occurs then the
partial record is padded out with zeroes when it is copied to the transient
program's DTA address.
3.22 SEQUENTIAL WRITE [FCB] (15H)
Parameters: C = 15H (_WRSEQ)
DE = Pointer to opened FCB
Results: L=A = 01H if error (disk full)
= 0 if write was successful
This function writes the 128 bytes from the current disk transfer address
to the file at the position defined by the current record and extent, which
are then incremented appropriately. The record count byte is kept updated
correctly if the file is extended or if the write moves into a new extent.
The file size in the FCB is also updated if the file is extended.
3.23 CREATE FILE [FCB] (16H)
Parameters: C = 16H (_FMAKE)
DE = Pointer to unopened FCB
Results: L=A = 0FFH if unsuccessful
= 0 if successful
This function creates a new file in the current directory of the specified
drive and opens it ready for reading and writing. The drive, filename and low
byte of the extent number must be set up in the FCB and the filename must not
be ambiguous. Checks will be done to ensure that invalid filenames are not
created.
If there is already a file of the required name then the action depends on
the value of the extent number byte. Normally this will be zero and in this
case the old file will be deleted and a new one created. However if the
extent number is non-zero then the existing file will be opened without
creating a new file. This ensures compatibility with early versions of CP/M
where each extent had to be explicitly created.
In all cases the resulting file will be opened with the required extent
number exactly as if an OPEN function call had been done.
3.24 RENAME FILE [FCB] (17H)
Parameters: C = 17H (_FREN)
DE = Pointer to unopened FCB
Results: L=A = 0FFH not if successful
= 0 if successful
The unopened FCB has the normal drive and filename, and also a second
filename starting at (DE+17). Every file in the current directory of the
specified drive which matches the first filename, is changed to the second
filename with "?" characters in the second filename leaving the appropriate
character unchanged. Checks are done to prevent duplicate or illegal
filenames from being created. Entries for sub-directories, hidden files and
system files will not be renamed.
3.25 GET LOGIN VECTOR (18H)
Parameters: C = 18H (_LOGIN)
Results: HL = Login vector
This function returns a bit set in HL for each drive which is available,
bit-0 of L corresponding to drive "A:". Up to eight drives ("A:" to "H:") are
supported by the system currently, so register H will usually be zero on
return.
3.26 GET CURRENT DRIVE (19H)
Parameters: C = 19H (_CURDRV)
Results: L=A = Current drive (0=A: etc)
This function just returns the current drive number.
3.27 SET DISK TRANSFER ADDRESS (1AH)
Parameters: C = 1AH (_SETDTA)
DE = Required Disk Transfer Address
Results: None
This function simply records the address passed in DE as the disk transfer
address. This address will be used for all subsequent FCB read and write
calls, for "search for first" and "search for next" calls to store the
directory entry, and for absolute read and write calls. It is not used by the
new MSX-DOS read and write functions. The address is set back to 80h by a
DISK RESET call.
3.28 GET ALLOCATION INFORMATION (1BH)
Parameters: C = 1BH (_ALLOC)
E = Drive number (0=current, 1=A: etc)
Results: A = Sectors per cluster
BC = Sector size (always 512)
DE = Total clusters on disk
HL = Free clusters on disk
IX = Pointer to DPB
IY = Pointer to first FAT sector
This function returns various information about the disk in the specified
drive. It is not compatible with CP/M which uses this function number to
return the address of an allocation vector. Note that unlike MSX-DOS 1, only
the first sector of the FAT may be accessed from the address in IY, and the
data there will only remain valid until the next MSX-DOS call.
3.29 RANDOM READ [FCB] (21H)
Parameters: C = 21H (_RDRND)
DE = Pointer to opened FCB
Results: L=A = 01H if error (end of file)
0 if read was successful
This function reads a 128 byte record from the file to the current disk
transfer address. The file position is defined by the three byte random
record number in the FCB (bytes 21h...23h). Unlike CP/M all three bytes of
the random record number are used. A partial record at the end of the file
will be padded with zeroes before being copied to the user's DTA.
The random record number is not altered so successive calls to this
function will read the same record unless the transient program alters the
random record number. A side effect is that the current record and extent are
set up to refer to the same record as the random record number. This means
that sequential reads (or writes) can follow a random read and will start
from the same record. The record count byte is also set up correctly for the
extent.
3.30 RANDOM WRITE [FCB] (22H)
Parameters: C = 22H (_WRRND)
DE = Pointer to opened FCB
Results: L=A = 01H if error (disk full)
= 0 if no error
This function writes a 128 byte record from the current disk transfer
address to the file, at the record position specified by the three byte
random record number (bytes 21h...23h). All three bytes of the random record
number are used. If the record position is beyond the current end of file
then un-initialized disk space will be allocated to fill the gap.
The random record number field will not be changed, but the current record
and extent fields will be set up to refer to the same record. The record
count byte will be adjusted as necessary if the file is being extended or if
the write goes into a new extent.
3.31 GET FILE SIZE [FCB] (23H)
Parameters: C = 23H (_FSIZE)
DE = Pointer to unopened FCB
Results: L=A = 0FFH if file not found
= 0 if file found OK
This function searches for the first match with the filename in the FCB,
exactly the same as OPEN FILE (function 0FH). The size of the located file is
rounded up to the nearest 128 bytes and the number of records determined. The
three byte random record field of the FCB is set to the number of records, so
it is the number of the first record which does not exist. The fourth byte of
the random record number is not altered.
3.32 SET RANDOM RECORD [FCB] (24H)
Parameters: C = 24H (_SETRND)
DE = Pointer to opened FCB
Results: None
This function simply sets the three byte random record field in the FCB to
the record determined by the current record and extent number. The fourth
byte of the random record number is not altered. No check is done as to
whether the record actually exists in the file.
3.33 RANDOM BLOCK WRITE [FCB] (26H)
Parameters: C = 26H (_WRBLK)
DE = Pointer to opened FCB
HL = Number of records to write
Results: A = 01H if error
= 0 if no error
Data is written from the current disk transfer address to the position in
the file defined by the random record number. The record size is determined
by the record size field in the FCB (bytes 0Eh and 0Fh) which must be set by
the user after opening the file and before calling this function. If the
record size is less than 64 bytes then all four bytes of the random record
number are used, otherwise only the first three are used.
The number of records to be written is specified by HL, and together with
the record size this determines the amount of data to be written. An error
will be returned if the size exceeds 64k, thus limiting the maximum size of a
transfer.
After writing the data, the random record field is adjusted to the next
record number in the file (ie. HL is added on to it). The current record and
extent fields are not used or altered. The file size field is updated if the
file has been extended.
The record size can be any value from 1...0FFFFh. Small record sizes are
no less efficient that large record sizes so if desired the record size can
be set to one and the record count then becomes a byte count. It is desirable
to write as much as possible with one function call since one large transfer
will be quicker than several small ones.
If the number of records to write (HL) is zero then no data will be
written, but the size of the file will be altered to the value specified by
the random record field. This may be either longer or shorter than the file's
current size and disk space will be allocated or freed as required.
Additional disk space allocated in this way will not be initialized to any
particular value.
3.34 RANDOM BLOCK READ [FCB] (27H)
Parameters: C = 27H (_RDBLK)
DE = Pointer to opened FCB
HL = Number of records to read
Results: A = 01H if error (usually caused by end-of-file)
= 0 if no error
HL = Number of records actually read
This function is the complement of the BLOCK WRITE function described above
and most of the same comments apply as regards its use. Again if large blocks
are read then it will be much faster than the normal CP/M operation.
For example if it is desired to read 20k from a file, it is better to read
the 20k with one function call rather than 20 separate function calls of 1k
each. However it makes no difference whether the 20k read is done with a
record size of 1 and a record count of 20k, with a record size of 20k and a
record count of 1, or any intermediate combination.
The number of records actually read is returned in HL. This may be smaller
than the number of records requested if the end of the file was encountered.
In this case any partial record will be padded out with zeroes before being
copied to the users DTA. The random record field is adjusted to the first
record not read, ie. the value returned in HL is added on to it.
3.35 RANDOM WRITE WITH ZERO FILL [FCB] (28H)
Parameters: C = 28H (_WRZER)
DE = Pointer to opened FCB
Results: L=A = 01H if error
= 00H if no error
This function is identical to RANDOM WRITE (function 22h) except that if
the file has to be extended, any extra allocated disk clusters will be filled
with zeroes before writing the data.
3.36 GET DATE (2AH)
Parameters: C = 2AH (_GDATE)
Results: HL = Year 1980...2079
D = Month (1=Jan...12=Dec)
E = Date (1...31)
A = Day of week (0=Sun...6=Sat)
This function simply returns the current value of the internal calender in
the format shown.
3.37 SET DATE (2BH)
Parameters: C = 2BH (_SDATE)
HL = Year 1980...2079
D = Month (1=Jan...12=Dec)
E = Date (1...31)
Results: A = 00H if date was valid
FFH if date was invalid
The supplied date is checked for validity and if it is valid then it is
stored as the new date. The validity checks include full checking for the
number of days in each month and leap years. If the date is invalid then the
current date will be left unaltered. The date is stored in the real time
clock chip so it will be remembered when the machine is turned off.
3.38 GET TIME (2CH)
Parameters: C = 2CH (_GTIME)
Results: H = Hours (0...23)
L = Minutes (0...59)
D = Seconds (0...59)
E = Centiseconds (always zero)
This function returns the current value of the system clock in the format
shown.
3.39 SET TIME (2DH)
Parameters: C = 2DH (_STIME)
H = Hours (0...23)
L = Minutes (0...59)
D = Seconds (0...59)
E = Centiseconds (ignored)
Results: A = 00H if time was valid
FFH if time was invalid
This function sets the internal system clock to the specified time value.
If the time is invalid then register A will be returned as 0FFh to indicate
an error and the current time will be left unaltered. The time is stored in
the real time clock chip and so it will be remembered and kept correct when
the machine is turned off.
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