DMO file format: Derive demo file

Introduction

A .DMO file is a demonstration for Derive, the computer algebra system for DOS made by Soft Warehouse of Honolulu. It is a plain text file of expressions to work through, with comment lines that say what each one shows. Derive’s help file lists a Demo command, “run demonstration in DMO file”. The copy of Derive 2 on this Mac came with six: ALGEBRA.DMO, ARITH.DMO, CALCULUS.DMO, FUNCTION.DMO, MATRIX.DMO and TRIG.DMO.

The syntax is the same as in a .MTH utility file, with one difference: comments are lines that start with a semicolon, and nothing is wrapped.

Structure

Like a utility file, a demo is lines of ASCII text ending in 0D 0A, with a 1A (Ctrl-Z) byte after the last line. All six files end that way. There is no signature and no header.

Line	Looks like	Meaning
Comment	`; Cross product of two vectors`	Starts with `;`, runs to the end of the line. It describes the expression that follows
Expression	`CROSS([1, 2, 3],[a, b, c])`	A Derive expression, a step of the demo. A definition such as `OUTER(v,w):=…` is a step like any other, and is used by the steps after it
Blank		Separates a step with its comment from the next

Unlike in a utility file, expressions are written as people type them: spaces round operators, no brackets round the argument of a function (LN 6 - LN 2, EXP LN x, DET [[1, a], [1, x]]), and a product by juxtaposition (2 x^3). The files use no ~ continuation (none of the six has a line ending in one), and long expressions stay on one line, up to 114 characters.

; Expands as necessary to simplify expressions
(x+a)^2-2*a*x

; Define OUTER to compute the outer product
OUTER(v,w):=VECTOR([ELEMENT(v,i)],i,DIMENSION(v)).[w]

; The outer product of two vectors
OUTER([a, b, c], [2, 3, 4])

Steps from ALGEBRA.DMO and MATRIX.DMO

The comment before an expression is its caption. Some steps have none, when the previous comment covers several lines of working, as in TRIG.DMO and FUNCTION.DMO.

A worked example

The first 0x30 bytes of ALGEBRA.DMO, and its last 16. The comment is a line of its own, and the expression after it starts at 0x30.

00000000: 3b20 4578 7061 6e64 7320 6173 206e 6563  ; Expands as nec
00000010: 6573 7361 7279 2074 6f20 7369 6d70 6c69  essary to simpli
00000020: 6679 2065 7870 7265 7373 696f 6e73 0d0a  fy expressions..
00000030: 2878 2b61 295e 322d 322a 612a 780d 0a0d  (x+a)^2-2*a*x...
…
000003d0: 2b79 5e32 2f78 5e32 2d32 2929 290d 0a1a  +y^2/x^2-2)))...

In the file viewer

The viewer shows the text coloured, with the comments in grey. The Overview tab has a table of the demo’s steps: the number of each, the comment before it, the expression (shortened) and its line. Text that does not read as Derive is not taken as a demo, which keeps the extension free for other formats that use it.

.MTH: a Derive utility file, the same syntax with definitions and expressions kept for loading.

Not described

This page is a partial reference, read from the six demonstration files of Derive 2 (each found in five copies on this Mac) and nothing else.

Item	Reference	Viewer
Playing a demo	Not checked against a running Derive: whether it shows each comment and waits for a key, and how it enters and simplifies each expression. That a comment is a caption and an expression a step is inferred from the file text	Does not play the demo or simplify anything; it lists the steps as text
Expression syntax	The typed forms seen in the six files are listed. The full grammar and the list of built-in functions are not given	Colours a fixed list of built-in function names, and does not check syntax
Comments	Only comments that start a line were seen. Whether a `;` later in a line is a comment is unknown	Treats only a line that starts with `;` as a comment
Later Derive versions	Demo files of later versions were not examined	Takes any text that reads as Derive
Step table	Not applicable	Each expression line is a step, and the comment lines before it are its caption, joined and shortened. Where several comment lines come before several expressions, the caption goes to the first expression only

.DMO File Format

Introduction

Structure

A worked example

In the file viewer

Not described

Links

Software

Reference

.DMO File Format

Introduction

Structure

A worked example

In the file viewer

Related files

Not described

Links

Software

Reference