The key benefit of RAM

The key benefit of RAM over types of storage which need physical movement is that retrieval times are short and consistent. Short because no physical movement is required, and consistent because the time taken to retrieve a piece of data does not depend on its current distance from a physical head; it requires practically the equal amount of time to access any piece of data stored in a RAM chip.

Because of this speed and consistency, RAM is used as 'main memory' or primary storage: the working area used for loading, displaying and manipulate applications and data. In most personal computers, the RAM is not an essential part of the motherboard or CPU—it comes in the easily upgraded form of modules called memory sticks or RAM sticks about the size of a few sticks of chewing gum, which can be quickly detached and replaced when they become damaged or too small for current purposes. A smaller amount of random-access memory is also integrated with the CPU, but this is usually referred to as "cache" memory, rather than RAM.

The disadvantage of RAM over physically moving media is cost and the loss of data when power is turned off. For these reasons, almost all PCs have disc storage as "secondary storage". Small PDAs and music players (up to 8 GiB in Jan 2007) may allot with disks, but rely on flash memory, to retain data between sessions of use.

Moore machine

Moore model control of a winch door in the theory of computation, a Moore machine is a finite state automaton where the outputs are determined by the current state alone. The state diagram for a Moore machine will include an output signal for each state. Compare with a Mealy machine, which maps transitions in the machine to outputs.

The name Moore machine comes from that of its supporter, Edward F. Moore, a state-machine pioneer who wrote "Gedanken-experiments on Sequential Machines".

Most digital electronic systems are designed as clocked sequential systems. Clocked sequential systems are a limited form of Moore machine where the state changes only when the global clock signal changes. Typically the current state is stored in flip-flops, and a global clock signal is connected to the "clock" input of the flip-flops. Clocked chronological systems are one way to solve met stability problems.

A typical electronic Moore machine includes a combinatorial logic chain to decode the current state into the outputs. The instant the current state changes, those changes ripple through that chain, and almost instantaneously the outputs change. There are design techniques to ensure that no glitches occur on the outputs during that brief period while those changes are rippling through the chain, but most systems are designed so that glitches during that brief transition time are ignored or are irrelevant. The outputs then stay the same indefinitely, until the Moore machine changes state again.

Sunglass

Sunglasses are a kind of visual correction aid, variously termed spectacles or glasses, which feature lenses that are colored or darkened to screen out strong light from the eyes.
Many people find direct sunlight too bright to be comfortable, particularly when reading from paper on which the sun directly shines. In outdoor activities like skiing and flying, the eye can receive more light than usual. It has been recommended to wear these kinds of glasses on sunny days to protect the eyes from ultraviolet radiation, which can lead to the development of a cataract. Sunglasses have also been linked with celebrities and film actors mainly due to the desire to mask identity, but in part due to the lighting involved in production being typically stronger than natural light and uncomfortable to the naked eye.

Vehicle

Vehicles are non-living means of moving. They are most often man-made, although some other means of moving which are not made by man can also be called vehicles; examples include icebergs and floating tree trunks. Vehicles may be propelled by animals, e.g. a chariot or an ox-cart. However, animals on their own, though used as a means of transportation, are not called vehicles. This includes humans carrying another human, for example a child or a disabled person. Vehicles that do not travel on land are often called crafts, such as watercraft, sail craft, aircraft, hovercraft and spacecraft most land vehicles have wheels. Please see the wheel article for examples of vehicles with and without wheels. Movement without the help of a vehicle or an animal is called locomotion. The word vehicle itself comes from the Latin vehicular.

History of Postage Stamp

The world's initial stamp was the Penny Black the adhesive postage stamp and the uniform postage rate were devised in Great Britain by James Chalmers around 1834. The same ideas were brought forward by Lovrenc Kosir, a Slovenian postal clerk at the Viennese court in 1835, but did not meet a positive reply. Later, the concept of the adhesive postage stamp was published by Rowland Hill, in Postal Reform: its Importance and Tractability in 1837. In it he argued that it would be better for the sender to pay the cost of release, rather than the addressee who could refuse the letter if they could not or did not want to pay, as sometimes happened at the time. He also argued for a uniform rate of one penny per letter, no matter where its destination. Accounting costs for the government would thus be cut; postage would no longer be charged according to how far a letter had traveled, which required each letter to have an individual entry in the Royal Mail's accounts. Chalmers' ideas were lastly adopted by Parliament in August, 1839 and the General Post Office launched the Penny Post service the next year in 1840 with two prepaid-postage pictorial envelopes or wrappers: one valued at a penny and one valued at two pence.

Three months shortly the first prepaid-postage stamp, known as the Penny Black was issued with the profile of Queen Victoria printed on it. Because the United Kingdom issued the first stamps, the Universal Postal Union grants it an exception from its rule that the recognition of the issuing country must appear on a stamp in Roman script for use in international mails. Previous to joining the U.P.U. many countries did not do this; there are very few violations of the rule since this time, though one example is the U.S. Pilgrim Tercentenary series, on which the country designation was involuntarily excluded. Because of this the numerous early issues of China and Japan often confound new collectors unfamiliar with Oriental scripts. A stamp must also show a face value in the issuing country's currency. Some countries have issued stamp with a letter of the alphabet or designation such as "First class" for a face value. Because of the U.P.U. rules their use is constrained to domestic mail, but breach of this rule is often tolerated. Exceptions to this are the British "E" stamp and the South African "International Letter Rate" stamp.