A Technical History of Apple's Operating Systems - Mac OS X Internals

56 Chapter 1 A Technical History of Apple’s Operating Systems
• 128KB RAM
• 20 bytes of parameter memory (PRAM) on a CMOS custom chip with
4.5 V user-replaceable backup battery
• Internal single-sided 3.5” floppy disk drive that accepted 400KB hard
shell floppy disks
• An external drive port with a DB-19 connector that allowed attachment
of a second drive
• Mouse port (DE-9 connector), and a mechanical tracking mouse with
optical shaft encoding at 3.54 pulses per mm (90 pulses per inch) of
travel
• Synchronous serial keyboard bus with an RJ-11 connector, and a
software-mapped 58-key keyboard
• Two RS-232/RS-422 serial ports (DE-9 connectors) for connecting modems,
printers, and other peripherals
• Four-voice sound generator with 8-bit digital/analog conversion and 22
kHz sampling rate
• 512×342-pixel bit-mapped black and white display on a 9-inch diagonal
CRT screen
• Physical dimensions of 13.6”×9.6”×10.9”, with a weight of 16 lb 8 oz
(7.5 kg), and a logic board area of 80 square inches
• No internal fan
The Macintosh ran a single-user, single-tasking operating system, initially
known as Mac System Software, which resided on a single 400KB floppy disk.
Many Macintosh programs were either conversions of, or influenced by, Lisa pro-
grams. Examples include MacPaint, MacProject, and MacWrite.
Unlike Lisa, the Macintosh was not designed to run multiple operating sys-
tems. The Macintosh ROM contained both low-level and high-level code. The low-
level code was for hardware initialization, diagnostics, drivers, and so on. The
higher-level Toolbox was a collection of software routines meant for use by applica-
tions, quite like a shared library. Toolbox functionality included the following.
• Management of dialog boxes, fonts, icons, pull-down menus, scroll bars,
and windows
• Event handling