lif

		 LIF: The Logical Interchange Format

This file describes the LIF media format, and the LIF file formats and
types used by the -41*, -71B, and -75* (*=series) products.

Numbers in this file are in decimal except where otherwise indicated.
Hexadecimal numbers are indicated by a prefix of 0x.



MEDIA TYPES

Any media can be used for LIF.  Three are known:

- Cassette tape
- 9114 diskette (3 1/2")
- Steinmetz & Brown disk drive (5 1/4", 40 tracks / disk, 2
heads/track, 9 sectors/track)

The block size is fixed at 256 bytes.  (The S&B disk drive stored two
blocks per 512 byte sector.)

All multi-byte data items are stored most significant byte first ("big
endian").  This is the same as the byte ordering used by M68000
processors and reversed from that used by Intel 8086 processors.



MEDIA FORMAT

A LIF volume is laid out in four parts:

- A header is stored in block 0.  It is always exactly one block long.

- Block one is an unused filler block and must be zeros (presumably
for header expansion).

- The directory is stored starting in block 2.  A field in the header
indicates how many records the directory occupies.

- The files themselves follow the directory, starting in block 2 +
directory length.

Each file is allocated a maximum length and occupies a continguous set
of blocks.  The files must be stored in the same order that their
directory entries are in.  However, unused blocks may appear anywhere
between files and unused directory entries may appear anywhere in a
directory.  (You may, for example, have an unused directory entry yet
have no space between the files.)



HEADER RECORD

starting	length
offset		in bytes	what

0		2	LIF identifier, must be 0x8000
2		6	volume label
8		4	directory start block, must be 2
12		2	LIF identifer for System 3000 machines, must be 0x1000
14		2	filler, must be zero
16		4	length of directory in blocks
20		2	LIF version number, must be 1
22		2	filler, must be zero
24		4	number of tracks per surface
28		4	number of surfaces
32		4	number of blocks per track
36		6	date and time that the volume was initialized[*]
40		216	filler, must be zero

[*] Date and time fields are in the format:

	year - 1900
	month
	day of month
	hour (0-23)
	minute
	second

with each value occupying one byte and stored in BCD.



DIRECTORY STRUCTURE

A directory consists of a sequence of 32-byte entries.  There are thus
8 entries per block.  The total number of files that can be stored is
thus fixed at volume initialization time to 8 * the number of
directory blocks.  A typical value is 768 files.

Each entry is in this format:

starting	length
offset		in bytes	what

0		10		file name (lower case mapped to upper,
				padded with trailing spaces)
10		2		file type
12		4		start block
16		4		allocated length in blocks[*]
20		6		date and time that the file was created
26		6		miscellaneous data[*]

[*] The method to determine the actual file length and the
interpretation of the miscellaneous data both vary depending on the
file type.



SECURE AND PRIVATE FILES

Many LIF files can be made secure and/or private.

A "secure" file is protected from modification, either by changing
(writing to or appending to) or deleting.  Making a file secure is
reversible.

A "private" file cannot be read from: it can only be executed.  If not
secure, it can be written to, but the values written cannot be read
back.  Privacy is not reversible: once a file has been made private,
it must remain that way.



FILE TYPES

Attribute codes:
	exe	the file is executable
	pri	the file can be made private
	sec	the file can be made secure or unsecure

========== General File Types ==========

type	attributes	description

0x0000			purged (deleted) file
0x0001	sec		standard LIF text file: -41* AS, -71B text, -75* LIF1
0xE0D0	sec		"standard" data file: -41* DA, -71B SDATA stream data
0xE0D5	sec		secure LIF text
0xFFFF			marks the last file used in a directory

For file type 0xE0D0: The miscellaneous data field contains these
values:

	0	unused
	1	unused
	2	high byte of (length of file in 8-byte registers)
	3	low byte of (length of file in 8-byte registers)
	4	bits 2^0 to 2^6	unused
		bit 2^7		set if file is secure
	5	unused, must be zero

For file type 0x0001: These files are made secure by changing the type
to 0xE0D5.

Formats:

0x0001	These files are a sequence of lines, with each line of the form:

		byte 0		high byte of (length of line in bytes)
		byte 1		low byte of (length of line in bytes)
		byte 2...n	text bytes

	If the length of the line is odd, a NUL byte is appended to
	the bytes 2...n but not the length.  For example, to write out
	the lines "abcd" and "efg", the following bytes are written:

		decimal	char

		0	^@
		4	^D
		97	a
		98	b
		99	c
		100	d
		0	^@
		3	^C
		101	e
		102	f
		103	g
		0	<pad>

	A line length of 0xFFFF signals the end of the file.

0xE0D0	array of 8-byte registers; each register is in -71B format,
	however -41*-type strings work

========== -41* File Types ==========

type	attributes	description

0xE020	sec		whole calculator including XMEM (HOSER ROM)
0xE030	sec		extended memory (HOSER ROM)
0xE040	sec		all of calculator
0xE050	sec		user keyboard
0xE060	sec		calculator status
0xE070	exe sec		ROM file
0xE080	exe pri sec	FOCAL program[*]
0xE0B0	sec		buffer (HOSER ROM)

For all of these files:

- The miscellaneous data field contains these values:

	0	unused
	1	unused
	2	high byte of (length of file in 8-byte registers - 1)
	3	low byte of (length of file in 8-byte registers - 1)
	4	bit 2^0		set if file is private
		bits 2^1 to 2^6	unused
		bit 2^7		set if file is secure
	5	unused, must be zero

[*] For these files, the length in bytes 2 and 3 is the length in
bytes - 1, not registers.

Formats:

0xE020	array of 7-byte registers
0xE030	array of 7-byte registers
0xE040	array of 7-byte registers
0xE050	array of 7-byte registers (keyboard definition registers only)
0xE060	array of 7-byte registers (status registers only)
0xE070	array of 10-bit words?
0xE080	see your favorite hex table
0xE0B0	array of 7-byte registers


========== -71B File Types ==========

type	attributes	description

0xE214	exe pri sec	Basic program
0xE215	exe pri sec	secure Basic program
0xE216	exe pri sec	private Basic program
0xE217	exe pri sec	secure & private Basic program

0xE204	exe pri sec	binary file (ROM image?)
0xE205	exe pri sec	secure binary file
0xE206	exe pri sec	private binary file
0xE207	exe pri sec	secure & private binary file

0xE0F0	sec		data file[*]
0xE0F1	sec		secure data file[*]

0xE20C	sec		keyboard definition
0xE20D	sec		secure keyboard definition

0xE208	exe pri sec	language extension
0xE209	exe pri sec	secure language extension
0xE20A	exe pri sec	private language extension
0xE20B	exe pri sec	secure & private LEX

For all of these files:

- The files are made private or secure by changing the file type:

	- add one to the type to make it secure
	- add two to the type to make it private
	- add three to the type to make it both secure and private

- The miscellaneous data field contains these values:

	0	unused
	1	unused
	2	high byte of (length of file in nybbles)
	3	middle byte of (length of file in nybbles)
	4	low byte of (length of file in nybbles)
	5	unused, must be zero

except for the files marked with [*].  For those files, the
miscellaneous data field contains these values:

	0	unused
	1	unused
	2	high byte of (length of file in records)
	3	low byte of (length of file in records)
	4	high byte of (length of record in bytes)
	5	low byte of (length of record in bytes)

Formats:

0xE214	don't know this format
0xE204	array of nybble ?
0xE0F0	These files are organized into records.  The record size is
	fixed within a file, but may vary from file to file and is
	given in the header.  If a data item does not fit in a record,
	the record is padded with 0xEF bytes and the data item starts
	on a new record.  However, the last record is padded with 0xFF
	bytes instead of 0xEF.

	The documentation indicates that 0xFF should always be and
	EOF.  However, the -71B didn't read the documentation and
	doesn't agree.  So on input treat both 0xFF and 0xEF as the same.

	Real numbers are exactly 8 byte long and are encoded in -71B
	internal format.  These numbers include NaN's, etc.

	Strings and are encoded in this form:

		byte 0		[*]
		byte 1		low byte of (length of string in bytes)
		byte 2		high byte of (length of string in bytes)
		byte 3..n	text data

	[*] If the entire string fits within a record, it is encoded as:

		byte 0		0xDF	entire string
			...	<from above>

	If the string does not completely fit within a record, it is
	encoded as:

		byte 0		0xCF	start of string
			...	<from above>
		byte 0		0x7F	middle of string (0 or more times)
			...	<from above>
		byte 0		0x6F	end of string
			...	<from above>

0xE20C	don't know this format
0xE208	array of nybble ?


========== -75* File Types ==========

Keyboard definitions are stored as LIF (not 75) text files.

type	attributes	description

0xE051	exe pri		ROM file
0xE052	pri		text file
0xE053	pri		appointment file
0xE088	exe pri		Basic file[*]
0xE089	exe pri		language extension
0xE08A	pri		VisiCalc worksheet file

[*] Data files are stored as Basic programs consisting only of DATA
statements.

For all of these files:

- There is no way to determine the actual file length from the header
alone: you must parse the file.

- The miscellaneous data field contains these values:

	0	0x80
	1	0x01
	2	password char 1
	3	password char 2
	4	password char 3
	5	password char 4

- All of these files can be made private by use of passwords.
Passwords are four characters long and are stored in bytes 2-5 of the
miscellaneous data field.  A password of four space characters means
that the file is not private.

Formats:

-75* files share a common header:

	starting	length
	offset		in bytes	what

	0		2	pointer to the next directory entry
	2		2	file length in bytes - 18
	4		1	file type
	5		1	file id letter
	6		4	date/time created
	10		8	file name (space characters on disk)
	18		10	?? (NUL characters on disk)

Also, all -75* files look a lot like tokenized Basic programs.

0xE051	array of byte?
0xE052	In these files, the file type of a text file is 0xBE and the
	file id letter is 0x54 ('T'). These files are a sequence of
	lines, with each line of the form:

		byte 0		low byte of (line number in BCD)
		byte 1		low byte of (line number in BCD)
		byte 2		number of characters in line + 1
		byte 3		space character (decimal 32)
		bytes 4..n	text bytes

	For example, line 1234 with the text "abc" would look like:

		decimal	char

		52	4	(0x34)
		18	^R	(0x12)
		4	^D
		32	 
		97	a
		98	b
		99	c

	The maximum line length is 126 characters.  The end of the
	file is indicated by an illegally-high line number of:

		0x99
		0xA9
		0x02	the threee bytes starting here may not be required
		0x8A
		0x0E

0xE053	don't know this format
0xE088	(This document describes DATA files only.)  In these files,
	the file type of a data file is the same as that of a Basic
	file, 0xFE and the file id letter is 0x42 ('B'). These files
	are a sequence of lines, with each line of the form:

		byte 0		low byte of (line number in BCD)
		byte 1		low byte of (line number in BCD)
		byte 2		length of rest of record in bytes + 1

	Real numbers have a length of 11 and are encoded in this form:

		byte 0		0x86
		byte 1		0x04
		bytes 2..9	number in -71B format
		byte 10		0x0E

	Integers have a length of 6 are are encoded in this form:

		byte 0		0x86
		byte 1		0x1A
		byte 2		low two digits of number in BCD
		byte 3		middle two digits of number in BCD
		byte 4		high two digits of number in BCD

	Integers may be in the range -99999 to 99999.  Positive
	numbers are stored as themselves.  Negative numbers are stored
	as 1,000,000 - the absolute value of the number.

	Strings have a length of 4 + the number of characters in the string
	and are encoded in this form:

		byte 0		0x86

		byte 1		0x05	or,	"-ed string constant
		byte 1		0x06	or,	unquoted string constant
		byte 1		0x96		'-ed string constant

		byte 2		number of characters in the string
		bytes 3...n-1	text bytes
		byte n		0x0E

	The maximum string length is 251 bytes.

	NaN's have a length of 11 and are encoded in this form:

		byte 0		0x86
		byte 1		0x04
		byte 2		0x11
		byte 3		0xF0
		bytes 4..9	0x00
		byte 10		0x0E

	The end of the file is indicated by an illegally-high line number of:

		0x99
		0xA9
		0x02
		0x8A	END statement
		0x0E

0xE089	array of byte?
0xE08A	standard VisiCalc?