Windows 3.0, 3.1, & 3.11 are operating environments. They are
not operating systems. They all require DOS, an OS, in order to run.
The first Windows was released in 1985 but it did not work. In 1990
Microsoft released Windows 3.0 and was reasonably stable. Windows
3.x overcame two of the limitations of DOS. It had co-operative multi-tasking
and a GUI, (graphic user interface). Because Windows 3.x rode on top of
DOS it could have only co-operative multi-tasking. Co-operative multi-tasking
had two major drawbacks: It had no way controlling CPU demand by the applications;
programs got an arbitrary time slice no matter the demand. If an application
crashed it crashed the entire system.
Graphical Environment Manager
GEM (Graphical Environment Manager) was a
windowing system created by
Digital Research, Inc. (DRI) for use with the
CP/M
operating system on the
Intel 8088
and
Motorola 68000
microprocessors. Later versions ran over
DOS as well.
GEM is known primarily as the graphical user interface (GUI) for the Atari ST
series of computers, and was also supplied with a series of IBM PC-compatible
computers from Amstrad. It was the core for a small number of DOS programs, the
most notable being Ventura Publisher. It was ported to a number of other
computers that previously lacked graphical interfaces, but never gained
popularity on those platforms. DRI also produced FlexGem for their FlexOS
realtime operating system.
History
GSX
GEM started life at DRI as a more general purpose graphics library known as
GSX (Graphics System eXtension), written by a team led by Lee Jay Lorenzen who
had recently left Xerox PARC (birthplace of the GUI). GSX was essentially a DRI-specific
implementation of the GKS graphics standard proposed in the late 1970s. GSX was
intended to allow DRI to write graphics programs (charting, etc.) for any of the platforms CP/M
would run on, a task that would otherwise require considerable effort to port
due to the large differences in graphics hardware (and concepts) between the
various systems of that era.
GSX consisted of two parts: a selection of routines for common drawing
operations, and the device drivers that are responsible for handling the actual
output. The former was known as GDOS and the latter as GIOS, a
play on the division of CP/M into machine-independent BDOS and machine-specific BIOS. GDOS was a
selection of routines that handled the GKS drawing, while GIOS actually used the
underlying hardware to produce the output.
GSX evolved into one part of what would later be known as GEM, which was an
effort to build a fully GUI system using the earlier GSX work as its basis.
Originally known as Crystal as a play on an IBM project called Glass,
the name was later changed to Gem, the use of the acronym evolved later
(see
backronym).
Under GEM, GSX became the GEM VDI, responsible for basic graphics and
drawing. VDI also added the ability to work with multiple fonts and added a
selection of raster drawing commands to the formerly vector-only GKS-based drawing commands. VDI also added multiple viewports,
a key addition for use with windows.
A new module, GEM AES (Application Environment Services),
provided the window management and UI elements, and GEM Desktop used both
libraries in combination to provide a Mac-like GUI. The 8086 version of the
entire system was first demoed at the 1984
COMDEX, and shipped as GEM/1 on 28 February 1985.
Later versions
At this point Apple Computer sued DRI in what would turn into a long dispute
over the "look and feel" of the GEM/1 system, which was an almost direct copy of
the Macintosh (with some elements bearing a closer resemblance to those in the
earlier Lisa). This eventually led to DRI being forced to change several basic
features of the system. Apple would later go on to sue other companies for
similar issues.
DRI responded with the "lawsuit friendly" GEM/2, which allowed the
display of only two fixed windows on the "desktop" (other programs could do what
they wished however), changed the trash can icon, and removed the animations for
things like opening and closing windows. It was otherwise similar to GEM/1, but
also included a number of bug fixes and cosmetic improvements.
The last commercial release was GEM/3 which had speed improvements and
shipped with a number of basic applications. Commercial sales of GEM ended with
GEM/3; the source code was subsequently made available to a number of DRI's
leading customers.
One-off versions
GEM/4 included the ability to work with Bézier curves, a feature still not
common outside the PostScript world. This version was produced specifically for
Artline a drawing program from CCP. The system also included changes to the font
management system, which made it incompatible with the likes of Timeworks
Publisher.
Another version of GEM called GEM/5 was produced by GST for Timeworks
Publisher 2.1. It contained an updated look with 3D buttons, font scaling on the
fly was included. It came complete with all the standard 3.1 tools. This version
was produced from GEM 3.13 with only the Bézier handling taken from GEM 4.
ViewMax
GEM Desktop itself was spun off as a product known as ViewMAX which was used
solely as a file management shell under DR-DOS. In this form the system could
not run other GEM programs. This led to the odd situation
where you could have a number of applications (including ViewMAX) all with their
own copy of the GEM system "inside" of them. This scenario was actually rare, as
there were not that many GEM programs.
In these forms GEM survived until DRI was purchased by Novell and all
GEM development was cancelled.
Throughout this time DRI had also been working on making the GEM system
capable of multitasking. This started with X/GEM based on GEM/1, but this
required use of one of the multitasking CP/M based operating systems. GEM/XM was
an updated version of GEM/2 which allowed multitasking and the ability to run
DOS programs in shell windows (as Windows does today). None of these saw the
light of day, but the GEM/XM source code is now freely available under the
GNU General Public License.
Lee Lorenzen had left soon after the release of GEM/1, when it became clear
that DRI had no strong interest in applications development. He then formed his
own company with another of the GEM developers, Dan Meyer, and started Ventura
Software. They developed Ventura Publisher, which was later marketed by Xerox
(and eventually to Corel), which would go on to be a very popular desktop
publishing program for some time.
Atari versions
Development of the production 68000 version of GEM began in September of
1984, when Atari sent a team called "The Monterey Group" toDigital
Research to begin work on porting GEM. Originally the plan was to run GEM on top
of CP/M-86k, both ostensibly ported to the Motorola 68000 by DRI prior to the ST
design being created. In fact, these ports were unusable and would require
considerable development. Atari eventually decided to give up on the existing
code and port a DOS-like operating system that DRI had experimented with
instead, GEMDOS. Development began in September of 1984 when Atari sent a team
called "The Monterey Group" to DRI to begin work on porting GEM and GEMDOS,
producing a system they referred to as TOS.
As Atari had provided most of the development of the 68k version, they were
given full rights to continued developments without needing to reverse-license
it back to DRI, who had apparently lost interest in the 68000 platform. As a
result, the Apple-DRI lawsuit did not apply to the Atari versions of GEM, and
they were allowed to keep a more Mac-like UI.
Over the next seven years, from 1985 to 1992, new versions of TOS would be
released with each new generation of the ST line. Updates included support for
more colors and higher resolutions in the raster-side of the system, but
remained generally similar to the original in terms of GKS support. In 1992
Atari released TOS 4, or MultiTOS, along with their final computer system, the
Falcon030. In combination with MiNT, TOS 4 allowed full multitasking support in GEM.
Continued development
Caldera Thin Clients (later known as Lineo, a division of the company now
known as the SCO Group), released the source to GEM under the General Public
Licence (GPL) in April 1999. The development of GEM for PC is continued as
OpenGEM and FreeGEM. It also has been ported to the Atari ST again to be used in
the free TOS clone EmuTOS.
Description
The "full" GEM system consisted of three main parts:
GEM VDI (Virtual Device Interface)
GEM AES (Application Environment Services)
GEM Desktop (an application providing drag-and-drop based file management)
The GEM VDI was the core graphics system of the overall GEM engine. It
was responsible for "low level" drawing in the form of "draw line from here to
here". VDI included a resolution and coordinate independent set of vector
drawing instructions which were called from applications through a fairly simple
interface. TVDI also included environment information (state, or context),
current color, line thickness, output device, etc.
These commands were then examined by GDOS, whose task it was to send the
commands to the proper driver for actual rendering. For instance, if a
particular GEM VDI environment was connected to the screen, the VDI instructions
were then routed to the screen driver for drawing. Simply changing the
environment to point to the printer was all that was needed (in theory) to
print, dramatically reducing the developer workload (they formerly had to do
printing "by hand" in all applications). GDOS was also responsible for loading
up the drivers and any requested fonts when GEM was first loaded.
One major advantage the VDI provided over the Macintosh was the way multiple
devices and contexts were handled. In the Mac such information was stored in
memory inside the application. This resulted in serious problems when attempting
to make the Mac handle pre-emptive multitasking, as the drawing layer (QuickDraw)
needed to have direct memory access into all programs. In GEM VDI however, such
information was stored in the device itself, with GDOS creating "virtual
devices" for every context – each window for instance. This advantage remained
largely theoretical however, as the multitasking versions of GEM were never
officially released.
The GEM AES provided the window system, window manager, UI style and
other GUI elements (widgets). For performance reasons, many of the GUI widgets
were actually drawn using character graphics. Compared to the Macintosh, AES
provided a rather spartan look and the system shipped with a single monospaced
font.
The AES performs its operations by calling the VDI, but in a more general
sense the two parts of GEM were often completely separated in applications.
Applications typically called AES commands to set up a new window, with the rest
of the application using VDI calls to actually draw into that window.
The GEM Desktop was an application program that used AES to provide a file
manager and launcher, the traditional "desktop" environment that users had come
to expect from the Macintosh. Unlike the Macintosh, the GEM Desktop was based on
top of DOS (MS-DOS
or DR DOS+ on the PC, TOS on the Atari), and as a result the actual display was
cluttered with computer-like items including path names and wildcards. In
general GEM was much more "geeky" than the Mac, but simply running a usable
shell on DOS was a huge achievement on its own.
