Specialised types of window managers
Several specialised types of window manager exist.

Virtual window managers
A virtual window manager is a window manager that uses virtual screens, whose resolution can be higher than the resolution of one's monitor/display adaptor. This environment is very useful when one wishes to have a large number of windows open at the same time. A number of virtual window managers have been made, including FVWM, Tvtwm, HaZe and others.

Tiling window managers
A tiling window manager is a window manager with an organization of the screen into mutually non-overlapping frames (hence the name tiling), as opposed to the traditional approach of coordinate-based stacking of objects (windows) that tries to emulate the desk paradigm.

How X window managers work
When a window manager is running, some kinds of interaction between the X server and its clients are redirected through the window manager. In particular, whenever an attempt to show a new window is made, this request is redirected to the window manager, which decides the initial position of the window. Additionally, most modern window managers are reparenting, which usually leads to a banner being placed at the top of the window and a decorative frame being drawn around the window. These two elements are controlled by the window manager rather than the program. Therefore, when the user clicks or drags these elements, it is the window manager that takes the appropriate actions (such as moving or resizing the window).

Computer systems
Most modern computer operating systems include information about time zones, including the capability to automatically change the local time when daylight savings starts and finishes (see the article on Daylight saving time for more details on this aspect).

[edit]
Microsoft Windows
Windows based computer systems normally keep system time as local time in a particular time zone. A system database of timezone information includes the offset from UTC and rules that indicate the start and end dates for daylight savings in each zone. Application software is able to calculate the time in various zones, but there is no standard way for users from multiple zones to use a single server and have their own local time presented to them.

Trivia
In terms of the largest number of time zones, Russia is first, with eleven time zones, including Kaliningrad on the Baltic Sea. The United States is tied with Canada for second with six time zones. If the possessions of the United Kingdom, the United States and France are included it increases the number of time zones in each. Taking into account overseas territories and possessions, France is the largest, with over twelve time zones, the United States has nine time zones, and the United Kingdom has over eight time zones.
In terms of area, China is the largest country with only one time zone (UTC+8), although before the Chinese Civil War in 1949 China was separated into five time zones. The next largest country with only one time zone is India (UTC+5:30). China also has the widest spanning time zone.

Skewing of zones
Time zones are based on the mean solar time of a particular meridian located in the middle of that zone with the boundaries of each zone located 7 1/2 degrees east and west of the meridian. In practice, zone boundaries are often drawn much farther to the west, and some locations base their time on meridians located far to the east. For example, Spain uses the mean solar time of 15 degrees east when it should use the time based on the prime meridian due to Spain's longitude. The tendency to draw time zone boundaries far to the west of their meridians is to utilize more daylight in the afternoon hours. Many of these locations also use daylight saving time which means that solar noon could occur as late as 2:00 P.M. by the clock.

Nautical time zones
Before 1920, all ships kept local apparent time on the high seas by setting their clocks at night or at the morning sight so that, given the ship's speed and direction, it would be 12 o'clock when the Sun crossed the ship's meridian (12 o'clock = local apparent noon). During 1917, at the Anglo-French Conference on Time-keeping at Sea, it was recommended that all ships, both military and civilian, should adopt hourly standard time zones on the high seas. A ship within the territorial waters of any nation would use that nation's standard time. The captain was permitted to change his ship's clocks at a time of his choice following his ship's entry into another time zone—he often chose midnight. These zones were adopted by all major fleets between 1920 and 1925 but not by many independent merchant ships until World War II.

History
Greenwich Mean Time (GMT) was established in 1675 as an aid to determine longitude at sea by mariners. The first time zone in the world was established by British railways on December 1, 1847 — with GMT hand-carried on chronometers. About August 23, 1852, time signals were first transmitted by telegraph from the Royal Observatory, Greenwich. Even though 98% of Great Britain's public clocks were using GMT by 1855, it was not made Britain's legal time until August 2, 1880. Some old clocks from this period have two minute hands — one for the local time, one for GMT [1]. This only applied to the island of Great Britain, and not to the island of Ireland.

Standard time zones
Originally, time zones based their time on Greenwich Mean Time (GMT, also called UT1), the mean solar time at longitude 0° (the Prime Meridian). But as a mean solar time, GMT is defined by the rotation of the Earth, which is not constant in rate. So, the rate of atomic clocks was annually changed or steered to closely match GMT. But on January 1, 1972 it became fixed, using predefined leap seconds instead of rate changes. This new time system is Coordinated Universal Time (UTC). Leap seconds are inserted to keep UTC within 0.9 seconds of UT1. In this way, local times continue to correspond approximately to mean solar time, while the effects of variations in Earth's rotation rate are confined to simple step changes that can be easily subtracted if a uniform time scale (International Atomic Time or TAI) is desired. With the implementation of UTC, nations began to use it in the definition of their time zones instead of GMT. As of 2005, most but not all nations have altered the definition of local time in this way (though many media outlets fail to make a distinction between GMT and UTC). Further change to the basis of time zones may occur if proposals to abandon leap seconds succeed.

Vista and Leopard features compared

September 19, 2006

The relative merits of the latest operating system releases from both Microsoft and Apple Computer have been debated at great length. PC Advisor got down and dirty with both packages to uncover the killer differences, and find out how they'll affect you, the end user.

This article appears in the November 06 issue of PC Advisor, onsale now in all good newsagents.

Vista vs Leopard
Backup and Restore Center vs Time Machine
Vista and Leopard have very similar approaches to backing up and restoring a system – Microsoft and Apple have both kept all the functions in a single location. Microsoft has concentrated on making the interface easier to understand and navigate, although Time Machine is arguably easier to use. But Time Machine’s space-themed interface won’t appeal to everyone.

a

b

c

d

e