Document revision date: 15 July 2002

Figure 1-5 shows the format of the record attributes area.

Figure 1-5 ACP-QIO Record Attributes Area

Table 1-9 lists the record attributes values and their meanings.

Table 1-9 ACP Record Attributes Values

Field Value	Meaning
FAT$B_RTYPE	Record type. Contains FAT$V_RTYPE and FAT$V_FILEORG.
FAT$V_RTYPE	Record type. The following bit values are defined: FAT$C_FIXED Fixed-length record FAT$C_VARIABLE Variable-length record FAT$C_VFC Variable-length record with fixed control FAT$C_UNDEFINED Undefined record format (stream binary) FAT$C_STREAM RMS stream format FAT$C_STREAMLF Stream terminated by LF FAT$C_STREAMCR Stream terminated by CR
FAT$V_FILEORG	File organization. The following bit values are defined: FAT$C_DIRECT Direct file organization 1 FAT$C_INDEXED Indexed file organization FAT$C_RELATIVE Relative file organization FAT$C_SEQUENTIAL Sequential file organization
FAT$B_RATTRIB	Record attributes. The following bit values are defined: FAT$M_FORTRANCC Fortran carriage control FAT$M_IMPLIEDCC Implied carriage control FAT$M_PRINTCC Print file carriage control FAT$M_NOSPAN No spanned records FAT$M_MSBRCW 4 Record count word (RCW) is MSB formatted
FAT$W_RSIZE	Record size in bytes.
FAT$L_HIBLK 2	Highest allocated VBN. The ACP maintains this field when the file is extended or truncated. Attempts to modify this field in a write attributes operation are ignored. FAT$W_HIBLKH High-order 16 bits FAT$W_HIBLKL Low-order 16 bits
FAT$L_EFBLK 2 3	End-of-file VBN FAT$W_EFBLKH High-order 16 bits FAT$W_EFBLKL Low-order 16 bits
FAT$W_FFBYTE 3	First free byte in FAT$L_EFBLK.
FAT$B_BKTSIZE	Bucket size in blocks.
FAT$B_VFCSIZE	Size in bytes of fixed-length control for VFC records.
FAT$W_MAXREC	Maximum record size in bytes.
FAT$W_DEFEXT	Default extend quantity.
FAT$W_GBC	Global buffer count.
FAT$W_VERSIONS	Default version limit; valid only if the file is a directory.

Figure 1-6 shows the format of the attributes statistics block. Table 1-10 lists the contents of this block.

Figure 1-6 ACP--QIO Attributes Statistics Block

Table 1-10 Contents of the Statistics Block

Field	Subfields	Meaning
SBK$L_STLBN		Contains the starting LBN of the file if the file is contiguous. If the file is not contiguous, this field contains a value of 0. The LBN appears as an inverted longword (the high- and low-order 16 bits are transposed for PDP-11 compatibility). The following subfields are defined:
	SBK$W_STLBNH	Starting LBN (high-order 16 bits)
	SBK$W_STLBNL	Starting LBN (low-order 16 bits)
SBK$L_FILESIZE		Contains the size of the file in blocks. The file size appears as an inverted longword (the high- and low-order 16 bits are transposed for PDP-11 compatibility). The following subfields are defined:
	SBK$W_FILESIZH	File size (high-order 16 bits)
	SBK$W_FILESIZL	File size (low-order 16 bits)
SBK$B_ACNT 1		Access count (low byte). Field is for PDP-11 compatibility.
SBK$B_LCNT 1		Lock count (low byte). Field is for PDP-11 compatibility.
SBK$L_FCB		System pool address of the file's file control block.
SBK$W_ACNT 1		Access count (number of channels with file open currently).
SBK$W_LCNT 1		Lock count (the number of access operations that have locked the file against writers).
SBK$W_WCNT 1		Writer count (the number of channels that currently have the file open for write).
SBK$W_TCNT 1		Truncate lock count (the number of access operations that have locked the file against truncation).
SBK$L_READS		Number of read operations executed for the file on this channel.
SBK$L_WRITES		Number of write operations executed for the file on this channel.

The following sections describe the operation of the major ACP functions. Each section describes the required and optional parameters for a particular function, as well as the sequence in which the function is performed. For clarity, when a major function invokes a subfunction, the input parameters used by the subfunction are omitted.

1.6.1 Create File

Create file is a virtual I/O function that creates a directory entry or a file on a disk device, or a file on a magnetic tape device.

The following is the function code:

• IO$_CREATE

The following are the function modifiers:

• IO$M_CREATE---Creates a file.
• IO$M_ACCESS---Opens the file on your channel.
• IO$M_DELETE---Marks the file for deletion (applicable only to disk devices).

The following are the device- or function-dependent arguments for IO$_CREATE:

• P1---The address of the file information block (FIB) descriptor.
• P2---The address of the file name string descriptor (optional).
• P3---The address of the word that is to receive the length of the resultant file name string (optional).
• P4---The address of a descriptor for a buffer that is to receive the resultant file name string (optional).
• P5---The address of a list of attribute descriptors (optional).

Table 1-11 lists fields in the FIB that are applicable to the IO$_CREATE operation.

Table 1-11 IO$_CREATE and the FIB

Field	Subfields	Meaning
FIB$L_ACCTL		Specifies field values that control access to the file. The following bits are applicable to the IO$_CREATE function:
	FIB$V_REWIND	Set to rewind magnetic tape before creating the file. Any data currently on the tape is overwritten.
	FIB$V_CURPOS	Set to create magnetic tape file at the current tape position. (Note: a magnetic tape file is created at the end of the volume set if neither FIB$V_REWIND nor FIB$V_CURPOS is set.) If the tape is not positioned at the end of a file, FIB$V_CURPOS creates a file at the next file position. Any data currently on the tape past the current file position is overwritten.
	FIB$V_WRITETHRU	Specifies that the file header is to be written back to the disk. If not specified and the file is opened, writing of the file header can be deferred to some later time.
FIB$W_CNTRLFUNC		Specifies the following value, which allows you to control actions subsequent to EOT detection on a magnetic tape file.
FIB$W_FID		Contains the file ID of the file created or entered.
FIB$W_DID		Contains the file identifier of the directory file.
FIB$W_NMCTL		Controls the processing of the file name in a directory operation. The following bits are applicable to the IO$_CREATE function:
	FIB$V_NEWVER	Set to create a file of the same name with the next higher version number. Only for disk devices.
	FIB$V_SUPERSEDE	Set to supersede an existing file of the same name, type, and version. Only for disk devices.
	FIB$V_LOWVER	Set on return if a lower numbered version of the file exists. Only for disk devices.
	FIB$V_HIGHVER	Set on return if a higher numbered version of the file exists. Only for disk devices.
FIB$W_VERLIMIT		Specifies the version limit for the directory entry created. Used only for disk devices and only when the first version of a new file is created. If 0, the directory default is used. If a directory operation was performed, FIB$W_VERLIMIT always contains the actual version limit of the file.
FIB$L_ACL_STATUS		Status of the requested ACL attribute operation, if any. The ACL attributes are included in Table 1-7. If no ACL attributes are given, SS$_NORMAL is returned here.

1.6.1.2 Disk ACP Operation

If the modifier IO$M_CREATE is specified, a file is created. The file ID of the file created is returned in FIB$W_FID. If the modifier IO$M_DELETE is specified, the file is marked for deletion.

If a nonzero directory ID is specified in FIB$W_DID, a directory entry is created. The file name specified by parameter P2 is entered in the directory, together with the file ID in FIB$W_FID. ( Section 1.3.1.1 describes the format for the file name string.) Wildcards are not permitted. Negative version numbers are treated as equivalent to a 0 version number. If a result string buffer and length are specified by P3 and P4, the actual file name entered, and its length, are returned.

The version number of the file receives the following treatment:

• If the version number in the specified file name is 0 or negative, the directory entry created gets a version number one greater than the highest previously existing version of that file (or version 1 if the file did not previously exist).
• If the version number in the specified file name is a nonzero number and FIB$V_NEWVER is set, the directory entry created gets a version number one greater than the highest previously existing version of that file, or the specified version number, whichever is greater.
• If the version number in the specified file name is a nonzero number and the directory already contains a file of the same name, type, and version, the previously existing file is set aside for deletion if FIB$V_SUPERSEDE is specified. If FIB$V_SUPERSEDE is not specified, the create operation fails with a SS$_DUPFILNAM status.
• If, after creating the new directory entry, the number of versions of the file exceeds the version limit, the lowest numbered version is set aside for deletion.
• If the file did not previously exist, the new directory entry is given a version limit as follows: the version limit is taken from FIB$W_VERLIMIT if it is a nonzero number; if it is 0, the version limit is taken from the default version limit of the directory file; if the default version limit of the directory file is 0, the version limit is set to 32,767 (the highest possible number).

The file name string entered in the directory is returned using the P3 and P4 result string parameters, if present. The file name string is also written into the header. If no directory operation was requested (FIB$W_DID is 0), the file name string specified by P2, if any, is written into the file header.

If an attribute list is specified by P5, a write attributes subfunction is performed (see Section 1.3.5).

If the modifier IO$M_ACCESS is specified, the file is opened (see Section 1.3.2).

If the extend enable bit FIB$V_EXTEND is specified in the FIB, an extend subfunction is performed (see Section 1.3.3).

Finally, if a file was set aside for deletion (IO$M_DELETE is specified), that file is deleted. If the file is deleted because the FIB$V_SUPERSEDE bit was set, the alternate success status SS$_SUPERSEDE is returned in the I/O status block. If the file is deleted because the version limit was exceeded, the alternate success status SS$_FILEPURGED is returned.

If an error occurs in the operation of an IO$_CREATE function, all actions performed to that point are reversed (the file is neither created nor changed), and the error status is returned to the user in the I/O status block.

1.6.1.3 Directory Entry Creation

Creating a new version of a file eliminates default access to the previously highest version of the file. For example, creating RESUME.TXT;4 masks RESUME.TXT;3 so the DCL command TYPE RESUME.TXT yields the contents of version 4, not version 3. To protect the contents of the earlier version of a file, the creator of a file must have write access to the previous version of a file of the same name.

1.6.1.4 Magnetic Tape ACP Operation

No operation is performed unless the IO$M_CREATE modifier is specified. The magnetic tape is positioned as specified by FIB$V_REWIND and FIB$V_CURPOS, and the file is created. The name specified by the P2 parameter is written into the file header label.

If P5 specifies an attribute list, a write attributes subfunction is performed (see Section 1.3.5).

If the modifier IO$M_ACCESS is specified, the file is opened (see Section 1.3.2).

1.6.2 Access File

This virtual I/O function searches a directory on a disk device or a magnetic tape for a specified file and accesses that file if found.

The following is the function code:

• IO$_ACCESS

The following are the function modifiers:

• IO$M_CREATE---Creates a file.
• IO$M_ACCESS---Opens the file on your channel.

The following are the device- or function-dependent arguments for IO$_ACCESS:

• P1---The address of the file information block (FIB) descriptor.
• P2---The address of the file name string descriptor (optional).
• P3---The address of the word that is to receive the length of the resultant file name string (optional).
• P4---The address of a descriptor for a buffer that is to receive the resultant file name string (optional).
• P5---The address of a list of attribute descriptors (optional).

Table 1-12 lists FIB fields that are applicable to the IO$_ACCESS operation.

Table 1-12 IO$_ACCESS and the File Information Block

Field	Subfields	Meaning
FIB$W_CNTRLFUNC		Specifies the value that allows the user to control actions subsequent to EOT detection on a magnetic tape file.
FIB$W_VERLIMIT		Receives the version limit for the file. Applicable only if FIB$W_DID is a nonzero number (if a directory lookup is done). Used only for disk devices.
FIB$L_ACL_STATUS		Status of the requested ACL attribute operation, if any. The ACL attributes are included in Table 1-7. If no ACL attributes are given, SS$_NORMAL is returned here. (For Files-11 C/D, this field is always set to SS$_NORMAL.)
FIB$L_STATUS		Alternate access status. The following bits are supported:
	FIB$V_ALT_REQ	Set to indicate whether the alternate access bit is required for the current operation. If not set, the alternate access bit is optional.
	FIB$V_ALT_GRANTED	If FIB$V_ALT_REQ = 0 and the alternate access check succeeded, the FIB bit returned from the file system is set.
FIB$L_ALT_ACCESS		A 32-bit mask that represents an access mask to check against file protection; for example, to open a file for read and to check whether it can be deleted. The mask has the same configuration as the standard protection mask.

1.6.2.2 Operation

If a nonzero directory file ID is specified in FIB$W_DID, a lookup subfunction is performed (see Section 1.3.1.) The version limit of the file found is returned in FIB$W_VERLIMIT.

If the directory search fails with a "file not found" condition and the IO$M_CREATE function modifier is specified, the function is reexecuted as a CREATE. In that case, the argument interpretations for IO$_CREATE, rather than those for IO$_ACCESS, apply.

If IO$M_ACCESS is specified, an access subfunction is performed to open the file (see Section 1.3.2).

If P5 specifies an attribute list, a read attributes subfunction is performed (see Section 1.3.5).

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