Shape tables are a feature of the
Apple II
Apple II ("apple Roman numerals, two", stylized as Apple ][) is a series of microcomputers manufactured by Apple Computer, Inc. from 1977 to 1993. The Apple II (original), original Apple II model, which gave the series its name, was designed ...
ROMs which allows for manipulation of small images encoded as a series of vectors. An image (or ''shape'') can be drawn in the high-resolution graphics mode—with scaling and rotation—via software routines in the ROM. Shape tables are supported via Applesoft BASIC and from machine code in the "Programmer's Aid" package that was bundled with the original Integer BASIC ROMs for that computer.
Applesoft's high-resolution graphics routines were not optimized for speed,
so shape tables were not typically used for performance-critical software such as games, which were typically written in
assembly language
In computing, assembly language (alternatively assembler language or symbolic machine code), often referred to simply as assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence bet ...
and used pre-shifted bitmap shapes. Shape tables were used primarily for static shapes and sometimes for fancy text; Beagle Bros offered a number of fonts in ''Font Mechanic'' as Applesoft shape tables.
Technical details
The
vector
Vector most often refers to:
* Euclidean vector, a quantity with a magnitude and a direction
* Disease vector, an agent that carries and transmits an infectious pathogen into another living organism
Vector may also refer to:
Mathematics a ...
s of a two-dimensional graphic, each encoding a direction from the previous pixel along with a flag indicating whether the new pixel should be illuminated or not, were encoded up to three in a byte. These were stored in a table via the Monitor or the
POKE
Poke may refer to:
Arts, entertainment, and media
* Poke (Ender's Game), Poke (''Ender's Game''), a fictional character
* Poke (game), a two-player card game
* Poke, a fictional bar owner in the television series ''Treme (season 2), Treme''
* The ...
command. From there, the graphic could be referenced by number (a table could contain up to 255 shapes), and built-in Applesoft routines permitted scaling, rotating, and drawing or erasing the shape. An
XOR
Exclusive or, exclusive disjunction, exclusive alternation, logical non-equivalence, or logical inequality is a logical operator whose negation is the logical biconditional. With two inputs, XOR is true if and only if the inputs differ (one ...
mode was also available to allow the shape to be visible on any color background; this had the advantage, also, of allowing the shape to be easily erased by redrawing it.
Apple did not provide any utilities for creating shape tables; they had to be created by hand, usually by plotting on
graph paper
Graph paper, coordinate paper, grid paper, or squared paper is writing paper that is printed with fine lines making up a regular grid. It is available either as loose leaf paper or bound in notebooks or graph books.
It is commonly found in mathe ...
, then calculating the hexadecimal values and entering them into the computer.
Beagle Bros
Beagle Bros was an American software company that specialized in creating personal computing products. Their primary focus was on the Apple II family of computers. Although they ceased business in 1991, owner Mark Simonsen permitted the Beagle B ...
created a shape table editing program, which eliminated the "number crunching", called ''
Apple Mechanic'', and a related program, ''
Font Mechanic''.
See also
*
Sprite
References
{{reflist
External links
Atariarchives.org example detailed instructions on assembling shape tables by hand
Computer graphics