Shape table
Encyclopedia
Shape tables were a powerful yet little-used feature of the early Apple II
ROMs, allowing for simple graphic manipulation on Apple II series
computers, using the "hi-res" (HGR/HGR2) graphics mode
. Shape tables were available from the BASIC interpreter in Applesoft BASIC
and from machine code in the "Programmer's Aid" package that was bundled with the original Integer BASIC
ROMs for that computer.
The vector
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
Apple did not provide any utilities for creating shape tables; they had to be created by hand, usually by plotting on graph paper, then calculating the hexadecimal values and entering them into the computer. Beagle Bros
created a shape table editing program, which eliminated the "number crunching", called Apple Mechanic, and a related program, Font Mechanic.
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 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.
Apple II
The Apple II is an 8-bit home computer, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977...
ROMs, allowing for simple graphic manipulation on Apple II series
Apple II series
The Apple II series is a set of 8-bit home computers, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977 with the original Apple II...
computers, using the "hi-res" (HGR/HGR2) graphics mode
Apple II graphics
The Apple II graphics were composed of idiosyncratic modes and settings that could be exploited. This graphics system debuted on the original Apple II, continued with the Apple II Plus and was carried forward and expanded with the Apple IIe, Enhanced IIe, IIc, IIc Plus and IIGS.- Peculiarity of...
. Shape tables were available from the BASIC interpreter in Applesoft BASIC
Applesoft BASIC
Applesoft BASIC was a dialect of Microsoft BASIC supplied with the Apple II series of computers. It superseded Integer BASIC and was the BASIC in ROM in all Apple II series computers after the original Apple II model. It was also referred to as FP because of the command used to invoke it instead...
and from machine code in the "Programmer's Aid" package that was bundled with the original Integer BASIC
Integer BASIC
Integer BASIC, written by Steve Wozniak, was the BASIC interpreter of the Apple I and original Apple II computers. Originally available on cassette, then included in ROM on the original Apple II computer at release in 1977, it was the first version of BASIC used by many early home computer owners...
ROMs for that computer.
The vector
Tuple
In mathematics and computer science, a tuple is an ordered list of elements. In set theory, an n-tuple is a sequence of n elements, where n is a positive integer. There is also one 0-tuple, an empty sequence. An n-tuple is defined inductively using the construction of an ordered pair...
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
POKEPEEK and POKEIn computing, PEEK is a BASIC programming language extension used for reading the contents of a memory cell at a specified address. The corresponding command to set the contents of a memory cell is POKE.-Statement syntax:...
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 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 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, then calculating the hexadecimal values and entering them into the computer. Beagle Bros
Beagle Bros
Beagle Bros was a software company that specialized in creating personal computing products that were both useful and whimsical. Their primary focus was on the Apple II family of computers.-History:...
created a shape table editing program, which eliminated the "number crunching", called Apple Mechanic, and a related program, Font Mechanic.
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 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.
External links
- Atariarchives.org example, detailed instructions on assembling shape tables by hand