of Microprocessors

352 MUSICAL ApPLICATIONS OF MICROPROCESSORS
The other method that is often found in alphanumeric display terminals
adds various graphic character shapes such as horizontal, vertical, and
diagonal lines and corners, junctions, arcs, etc., to the character set. The
user can then select line segments from this set and piece images together
that appear to be of high resolution. While excellent for images such as game
boards, bar charts, and other highly structured material, the technique is
quite limited on arbitrary lines and curves such as music-control functions
and waveforms.
Bit-Mapped Display Interfaces
Thus, for any kind of serious graphics work a true bit-mapped or pixel
display is a necessity. The term bit-mapped means that every point on the
display literally corresponds to a bit in the display memory, whereas pixel
refers to the fact that individual picture elements can be manipulated.
Most integrated personal computers today have some form of bitmapped
graphics display capability. Integrated here means that the display
generation circuitry is part of the computer as opposed to a separate display
terminal. Even the under-$200 Commodore-64 has a 320 X 200 pixel
resolution in its two-color mode. The Apple llline typically provides 280 X
192, although the newest members also have a 560 X 192 mode, which is
quite a resolution mismatch. Pixel graphics is not really standard on the IBM
PC, but most users purchase the option (usually to run "business graphics"
software), which offers an even more mismatched 640 X 200 resolution in
the monochrome mode. Many IBM "clones" offer better graphics capability
as a standard feature; the Tandy 2000, for example, has 640 X 400
resolution even in the eight-color mode. The Apple Maclntosh is currently
the best-known low-cost graphics-oriented computer. Its 512 X 342
resolution, although not the highest around, is well balanced and backed up
by a microprocessor (68000) that is ideally suited to graphics manipulations.
Unfortunately, its "closed" architecture makes connection to synthesis
equipment and user programming of signal-processing-oriented graphics
software much more complex than necessary, although its built-in software
can be of some use.
Larger bus-oriented and multiuser computers typically use separate
display terminals rather than integrated display generators. Usually, such
terminals are alphanumeric with perhaps some line segment character shapes
available. Full graphics terminals are available, however, as are graphics
retrofit kits for some of the more popular alphanumeric units. Graphics
programming, particularly graphics editing, which will be described, of
such a terminal is difficult and slow due to the serial communication link
between terminal and computer.