Os

Classic Mac OS

The MacOS also introduced a new type of filesystem, which contained two different "forks" for a file. It was innovative at the time for separating out parameters into the resource fork, and raw data in the "data fork". However, it became quite a challenge to interoperate with other operating systems which did not recognize such a system.

The term "Mac OS" was not officially used until 1996 with the release of Mac OS 7.6 - prior to that the Macintosh operating system software was simply known as "The System", or by its version number, e.g. System 6 or System 7. Another common term was "the Toolbox". Apple deliberately played down the existence of the operating system in the early years of the Mac to help make the machine appear more user-friendly and to distance it from other systems such as MS-DOS, which were portrayed as arcane and technically challenging. With Mac, you turned it on, it just worked.

By the late 1990s, it was clear the useful life of this 1980s-era technology was coming to an end, with other more stable multitasking operating systems being developed.

There are a variety of views on how the Macintosh was developed, and where the underlying ideas originated. While the connection between the Macintosh and the Alto project at Xerox PARC has been established in the historical record, the earlier contributions of Ivan Sutherland's Sketchpad and Doug Engelbart's On-Line System are no less significant. See History of the GUI, and Apple v. Microsoft.

• Mac OS X and its history
• Mac OS X Server

Software

• Address Book
• AppleWorks
• Backup
• Chess
• Darwin Mach-based core OS
• Developer Tools
• DVD Studio Pro
• Final Cut Express
• Final Cut Pro
• HyperCard
• iCal
• iChat
• iDVD
• iLife
• iMovie
• iPhoto
• iSync
• iTunes
• Keynote
• MacDraw
• MacPaint
• MacWrite
• Mail
• Preview
• QuickTime
• QuickTime Streaming Server
• Apple Remote Desktop
• Safari web browser
• Shake
• Sherlock
• SimpleText
• Soundtrack
• TeachText
• TextEdit
• WebObjects
• X11

Made by other organizations and/or people

• Audacity
• FileMaker (FileMaker, Inc., an Apple subsidiary)
• iCab
• LimeWire
• Logic (Emagic Gmbh, an Apple subsidiary)
• MindWrite - Word processor, outliner, and sorter, no longer produced.
• Stuffit Expander
• Taste - Word processor, no longer produced.
• Watson - web services

What is today Mac OS X originally started in 1989 as NeXTSTEP, the object-oriented operating system developed by Steve Jobs' NeXT company after he was forced from Apple in 1986. After disappointing sales of the computers designed to run it, NeXTSTEP was ported to a number of other platforms in the early 1990s, but never became very popular because of the arguably high pricing that NeXT applied to its products, especially for its development tools. NeXT had justified this, saying that high prices accompany high quality, though many were not willing to take the NeXT route, beneficial or not. NeXTSTEP then underwent an evolution into OPENSTEP, which separated the object layers from the operating system below, allowing it to run with less modification on other platforms. However by this point in time a number of other companies, notably Apple, IBM and Microsoft, were claiming that they would soon be releasing similar object-oriented operating systems and development tools of their own - however some of these efforts such as Taligent did not fully come to fruition.

Coincident with these developments, by the mid-1990s Apple's own operating system had reached the limits of its single-user, co-operative multitasking architecture. A massive development effort to replace it, known as Copland, was started in 1994, but was generally realized outside of Apple to be a hopeless case due to political infighting. By 1996 Copland was nowhere near ready for release, and the effort was eventually cancelled outright. Some elements of Copland were incorporated in Mac OS 8, released in 1997.

At this point the new CEO of Apple turned to the market to look for a replacement - a modern operating system with the UI Apple users expected, and the performance and modern features needed to move the platform forward. After some time, and a publicly rancorous debate, OPENSTEP was selected as the basis and Apple purchased NeXT outright.

At first the plan was to develop a new operating system based almost entirely on OPENSTEP, with an emulator for running "classic" Macintosh applications. The result was known under the code name Rhapsody, slated for release in 1998. It was expected that developers would port their software to the considerably more powerful OPENSTEP libraries once they learned of its power and flexibility, instead, perhaps unexpectedly, the vast majority of developers told Apple that this would never occur, and that they would rather leave the platform entirely. Interestingly enough, the newer Cocoa libraries developed by Apple are almost entirely identical to the original OPENSTEP libraries, and are recently coming into greater use.

Another re-design was then started, this time promoting the original Macintosh APIs, re-written as Unix libraries, as first-class citizens of the new operating system. Another change was required by the switch from OPENSTEP's Display PostScript engine to one that was license free, known as Quartz. The resulting changes delayed the introduction of the operating system by about two years.

During this time the lower layers of the operating system, consisting of the Mach kernel and the BSD layers on top, was re-packaged and released under an open source license as Darwin. The Darwin kernel provides an extremely stable and flexible operating system which rivals many other Unix implementations, however it is unclear if it sees any real use outside the Macintosh community.

• Mac OS X Public Beta
  • Switch to BSD-derived Darwin core operating system
  • New Quartz/Aqua GUI
  • Includes Mac OS 9.1, which it runs in a virtual machine
• Mac OS X 10.0 - codenamed Cheetah
• Mac OS X 10.1 - codenamed Puma, major speedups
• Mac OS X 10.2 - codenamed Jaguar, introduced many new features:
  • Increased support for Microsoft Windows networks
  • Quartz Extreme for compositing graphics directly on the video card
  • An adaptive spam email filter
  • A system-wide repository for contact information in the new Apple Address Book
  • Apple Rendezvous networking
  • iChat, an Apple-branded, officially-supported third party AOL Instant Messenger client
  • A revamped Finder with searching built directly into every window
  • Dozens of new Apple Universal Access features
  • Sherlock 3: Web services (See Watson)
  • Increased speed across the entire system
• Mac OS X 10.3 - codenamed Panther, released in October 2003, Among the over 150 new features:
  • Updated Finder, incorporating a brushed-metal interface and fast-searching
  • Exposé, a new system to manipulate windows
  • Fast User Switching that allows a user to remain logged in while another user logs in
  • iChat AV video-conferencing software
  • Improved PDF Rendering to allow for extremely fast PDF viewing
  • Built-in faxing support
  • Much greater Microsoft Windows compatibility
  • FileVault: on the fly encryption and decryption of a user's home folder
  • Increased speed across the entire system with more support for the G5

Software

• Apple Address Book
• Apple Mail - email client
• Apple Preview
• Apple Script Editor - for editing AppleScripts
• Apple X11
• iCal - calendar management
• iChat AV - instant messaging and video conferencing
• iMovie - video editing
• iPhoto - photo cataloging
• iTunes - music cataloging and purchasing
• QuickTime Player
• Safari - web browser
• Sherlock - file searching (version 2), web services (version 3)

Press release

...combines the power and stability of UNIX with the simplicity and elegance of the Macintosh.

...innovative time-saving features including a new Finder and the Dock designed to help you navigate and organize your system, and give you instant access to your most frequently used applications, folders....

...built on three cutting-edge graphics technologies Quartz, OpenGL, and QuickTime...

...the foundation of Mac OS X [is] an industrial-strength, UNIX-based core operating system—called Darwin—that delivers unprecedented stability and performance...powerful, advanced features such as protected memory, preemptive multitasking, advanced memory management, and symmetric multiprocessing...

...Seamless device connectivity and industry-leading applications...

...includes powerful, easy-to-use tools for making your own movies, managing your music, and capturing photos from your digital camera. Built-in support for burning music and data CDss, playing DVD movies, and even authoring your own DVDs...

...lets you run thousands of existing Mac OS 9-compatible applications, while... Mac OS X provide[s] a foundation for great new applications.

• UNIX
• GNU/Linux
• TOS
• Microsoft Windows
• Mac OS
• MVS
• Netware
• OpenVMS

Classifications and Terminology

An operating system is conceptually broken into three sets of components: a shell, a kernel and low-level system utilities. As the name implies the shell is an outer wrapper to the kernel which in turn talks directly to the hardware.

           Hardware <-> Kernel <-> Shell <-> Applications 

Kernel design ideologies include those of the monolithic kernel, the microkernel and the exokernel. Traditional commercial systems such as UNIX and Windows use a monolithic approach, the trend in more modern systems is to use a microkernel (such as in QNX, BeOS, Windows NT etc) there are a few exceptions such as Linux which still use a monolithic kernel . The microkernel approach is also very popular among research OSes. Many embedded systems use ad-hoc exokernels.

• History of operating systems
• List of operating systems
• Hard disk drive partitioning
• LiveCD OS (Gnoppix and Knoppix Linux).
• monolithic kernel -- microkernel -- exokernel
• asymmetric and symmetric multiprocessing (SMP) -- clustering -- distributed computing
• Operating system advocacy
• real-time operating system -- time-share -- multitasking -- embedded system -- single-user -- multi-user
• orthogonally persistent -- capabilities versus access control lists
• object-oriented operating system

External links

During the next twenty years about a third of England and Wales was mapped at the one-inch scale. It was gruelling work: Major Thomas Colby, later the longest serving Director General of the Ordnance Survey, walked 586 miles in 22 days on a reconnaissance in 1819.

In 1824, Colby and most of his staff moved to Ireland, to work on a six inch to the mile valuation survey. Colby was not only involved in the design of specialist measuring equipment. He also established a systematic collection of place names, and reorganised the map-making process to produce clear, accurate plans. He believed in leading from the front, travelling with his men, helping to build camps, and as each survey session drew to a close arranging mountain-top parties with enormous plum puddings.

After the first Irish maps began to come out in the mid-1830s, the Tithe Commutation Act led to calls for similar six-inch surveys in England and Wales. After official prevarication, the development of the railways added to pressure that resulted in the 1841 Ordnance Survey Act. This granted a right to enter property for the purpose of the survey.

Following a fire at its headquarters in the Tower of London, the OS was in disarray for several years with arguments about which scales to use. Major-General Sir Henry James was now Director General, and he saw how photography could be used to make maps of various scales cheaply and easily. The twenty five inch to the mile survey was complete by 1895.

The Davidson Committee was established in 1935 to review the Ordnance Survey's future. The new Director General, Major-General Malcolm MacLeod, started the retriangulation of Great Britain, an immense task which involved erecting concrete triangulation pillars on prominent hilltops throughout Britain.

The Davidson Committee's final report set the OS on course for the twentieth century. The National Grid reference system was launched, with the metre as its measurement. An experimental new 1:25,000 scale map was introduced. The one-inch maps remained for almost forty years before being superseded by the 1:50,000 scale series, as proposed by William Roy more than two centuries earlier.

In 1995 the Ordnance Survey digitised the last of about 230,000 maps, making Britain the first country in the world to complete a programme of large-scale electronic mapping.

• 1:50,000
  • Landranger - These are designed as road maps. They have pink covers and 204 of them cover the whole of the UK.
• 1:25,000
  • Explorer - Designed for walkers and cyclists. There are 351 of these maps at the time of writing, but the number is increasing. They have orange covers.
  • Explorer OL - Also for walkers & cyclists. These 33 maps specifically cover tourist destinations. Identified by their yellow covers and often double-sided, they predate the explorer maps. Previously known as Outdoor Leisure maps.
  • Pathfinder - Pathfinders were the predecessors to the Explorer and Explorer OL maps. These maps were smaller than the new ones and generally had no overlap between adjacent sheets, meaning that even a short walk may require three or four different maps and a long one may range over even more. For this reason they have recently been gradually phased out.

There is a difference between the grid used in the mapping of Ireland compared to mainland Britain and the Scottish islands. This sectional concentrates on the traditional mainland reference system, called OSGB36 ™ (Ordnance Survey Great Britain 1936) used after the retriangulation of 1936-1953.

The maps are based on the projection called the Airy 1830 ellipsoid, with an origin at 49 ° N, 2 ° W. The ellipsoid is a regional best fit for Britain, more modern mapping tend to use the GRS80 ellipsoid used by the GPS. Over the Airy projection of Britain a straight line grid, the National Grid, is placed with a new false origin (to eliminate negative numbers), creating a 400 km by 100 km grid. The distortion created between the OS grid and the projection is countered by a scale factor in the longitude to create two lines of longitude with zero distortion rather than one. The produced maps contain a small variation between true north and grid north.

The position of a point on an OS map is given in northings (east-west) and eastings (north-south) in metres from the origin. To prevent very large values metre values the gird is divided. At the highest level into 25 500 km by 500 km squares, each with a letter code from A to Z (omitting I) starting with A in the north-west corner to Z in the south-east corner. This is much larger than the islands mapped, only four grid squares actually contain land - S,T,N, and H. Each large square is subdivided again into 25 100 km by 100 km squares, using the same lettering system. The created grid produces the following squares containing land:

				hp
			ht	hu
	hw	hx	hy	hz
na	nb	nc	nd
nf	ng	nh	nj	nk
nl	nm	nn	no
	nr	ns	nt	nu
	nw	nx	ny	nz
		sc	sd	se	ta
		sh	sj	sk	tf	tg
	sm	sn	so	sp	tl	tm
	sr	ss	st	su	tq	tr
sv	sw	sx	sy	sz	tv

As the above information indicates a geodetic transformation between OSGB36 and other terrestrial reference systems (like ITRF2000, ETRS89, or WGS84) can be quite tedious, if attempted manually. The process is called a Helmert datum transformation, the transformation from ETRS89 to OSGB36 is called the National Grid Transformation OSTN02.

See also:

• Cartography (map making)
• Hydrography
  • Hydrographic survey
  • United Kingdom Hydrographic Office
• Sea level
• UK topics

External Links

Notable Characteristics

Due to its very high density osmium is generally considered to be the heaviest known element narrowly defeating iridium. However, calculations of density from the space lattice may produce more reliable data for these elements than actual measurements and give a density of 22650 for iridium versus 22661 for osmium. Definitive selection between the two is therefore not possible at this time. It's just too close to call.

Occurrence

Compounds

Isotopes

Precautions

External Links