HP MPE/iX 6.x Operating System intrinsic, MPE/iX command :FILE, Specifying a Record Size

Table 6-5. Comparison of Logical Record Formats

Fixed-length	Variable-length	Unde￿ned-length
File System knows data length	File System knows data length	File System does not kno w data
		length
All records same length	Record length varies	Record length v aries
Record space contains only data	Record space contains data plus	Record space con tains data plus
	byte count	￿ller
Request actual record size	Request maximum record size	Request maximum record size

Specifying a Record Size

You can specify the size of records in y our ￿le by using one of the follo wing: MPE/iX command :BUILD (for disc ￿les)

MPE/iX command :FILE

HPFOPEN or FOPEN intrinsic

You can specify your own record size or accept the default size for the device y ou are using. MPE/iX default record sizes for devices are sho wn in Table 6-6. Subsystem defaults may be di￿erent from MPE/iX defaults. F or example, the Editor default can be 72 or 80 bytes, depending on the text format, while the MPE/iX standard default is the record size con￿gured for the device. F or detailed information on specifying a record size, refer to Accessing Files Pr ogrammer's Guide (32650-90017).

Table 6-6. Standard Default Record Sizes

Device	Record Size (Bytes)
Disc	256
Magnetic tape unit
	256
Terminals (most)
	80*
Line printer	132*
Plotter
	510
	* Controlled by con￿gured
	record length.

The File System sets up all records (ASCII and binary) to begin on 2-b yte boundaries for device ￿les. Even if you specify an odd-b yte record, the next record cannot begin in the next byte. In this case, the File System adjusts the record size b y adding one byte to make the next record begin on a w ord boundary. If the ￿le is ASCII, the extra b yte is made inaccessible

6-24 File System