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Flex09 User Manual
Disk Files and their Names

All disk files are stored in the form of 'sectors' on the disk and in this version, each sector contains 256 bytes of information. Each byte can contain one character of text or one byte of binary machine information. A maximum of 340 user-accessible sectors will fit on a single-sided mini disk or 1140 sectors on a single-sided full size floppy. Double-sided disks would hold exactly twice that number of sectors. Double-density systems will hold more still. The user, however, does not keep count, for the system does this automatically. A file will always be at least one sector long and can have as many as the maximum number of sectors on the disk. The user should not be concerned with the actual placement of the files on the disk since this is done by the operating system. File deletion is also supported and all previously used sectors become immediately available again after a file has been deleted.

All files on the disk have a name. Names such as the following are typical:


Anytime a file is created, referenced, or deleted, its name must be used. Names can be most anything but must begin with a letter (not numbers or symbols) and be followed by at most 7 additional characters, called 'name characters'. These 'name characters' can be any combination of the letters 'A' though 'Z' or 'a' through 'z', any digit '0' through '9', or one of two special characters, the hyphen '-' or the underscore '_', (a left arrow on some terminals).

File names must also contain an 'extension'. The file extension further defines the file and usually indicates the type of information contained therein. Examples of extensions are: TXT for text files, BIN for machine readable binary files, CMD for utility command files, and BAS for BASIC source programs. Extensions may also contain up to 3 'name characters' with the first character being a letter. Most of the FLEX commands assume a default extension on the file name and the user need not be concerned with the actual extension on the file. The user may at anytime assign new extensions, overiding the default value, and treat the extension as just part of the file name. Some examples of file names with their extensions follow:


Note that the extension is always separated from the name by a period '.'. The period is the name 'field separator'. It tells FLEX to treat the following characters as a new field in the name specification.

A file name can be further refined. The name and extension uniquely define a file on a particular drive, but the same name may exist on severla drives simultaneously. To designate a particular drive a 'drive number' is added to the file specification. It consists of a single digit (0-3) and is separated from the name by the field separator '.'. The drive number may appear either before the name or after it (after the extension if it is given). If the drive is not specified, the system will default to either the 'system' drive or the 'working' drive. These terms will be described a little later.

Some examples of file specifications with drive numbers follow:


In summary, a file specification may contain up to three fields separated by the field separator. These fields are: 'drive', 'name', and 'extension'. The rules for the file specification can be stated quite concisely using the following notation:


The '<>' enclose a field and do not actually appear in the specification, and the '[]' surround optional items of the specification. The following are all syntactically correct:


Note that the only required field is the 'name' itself and the other values will usually default to predetermined values. Studying the above examples will clarify the notation used. The same notation will occur regularly throughout the manual.

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