Calculator

A calculator is a machine for performing calculations. Although modern calculators often incorporate a general purpose computer, the device is calculated for performing specific operations, rather than for flexibility. Modern calculators are more convenient than most computers, though some PDAs are comparable in amount to handheld calculators.

In the past, some calculators were as huge as today's computers. The first automatic calculators were mechanical desktop devices which were replaced by electromechanical desktop calculators, and then by electronic devices using first thermionic valves, then transistors, then hard-wired integrated circuit logic. New calculators are electrically powered and come in innumerable shapes and sizes varying from cheap, give-away, credit-card sized models to more sturdy adding machine-like models with built-in printers.

Indicator

Dial indicators are instruments used to correctly measure a small distance. They may also be known as a Dial gauge, Dial Test Indicator, or as a clock. They are named so because the measurement results are displayed in a overstated way by means of a dial. They may be used to check the dissimilarity in tolerance during the check process of a machined part, measure the deflection of a beam or ring under laboratory conditions, as well as many other situations where a small measurement needs to be registered or indicated.

An economic indicator is a statistic concerning the economy. The lighting system of a motor vehicle consists of lighting and signaling procedure mounted or integrated to the front, sides and rear of the vehicle. The purpose of this system is to present illumination for the driver to operate the vehicle safely after dark, to increase the visibility of the vehicle, and to display information about the vehicle's presence, position, size, direction of travel, and driver's intentions concerning direction and speed of travel.

Reliability

In computer networking, a reliable protocol is one that ensures that reliability properties with respect to the delivery of data to the intended recipient(s), as opposed to an unreliable procedure, which does not guarantee that data will be delivered intact, or that it will be delivered at all. A reliable multicast protocol may ensure consistency on a per-recipient basis, as well as provide strong reliability properties that relate the delivery of data to different recipients, such as e.g. total order, atomicity, or virtual synchrony.

Reliable protocols normally incur more overhead than unreliable protocols, and as a result, are slower and less scalable. This often isn't an issue for unicast protocols, but it may be a difficulty for multicast protocols. TCP, the main protocol used in the Internet today, is a reliable unicast protocol. UDP, often used in computer games or other situation where speed is an issue and the loss of a little fact is not, is an unreliable unicast protocol.

Table

In relational databases, SQL databases, and flat file databases, a table is a set of data elements that is controlled using a model of horizontal rows and vertical columns. The columns are identified by name, and the rows are identified by the values appearing in a particular column division which has been identified as a candidate key. Table is another term for family although there is the difference in that a table is usually a multi-set of rows whereas a relation is a set and does not allow duplicates. A table has a particular number of columns but can have any number of rows. Besides the actual data rows, tables generally have related with them some meta-information, such as constraints on the table or on the values within particular columns.

The data in a table does not have to be actually stored in the database. Views are also relational tables, but their data is considered at query time. In non-relational systems, such as hierarchical databases, the isolated counterpart of a table is a structured file, representing the rows of a table in each record of the file and each column in a record.

Trams

Electric-powered trams were first successfully experienced in service in Richmond, Virginia, in 1888, in the Richmond Union Passenger Railway built by Frank J. Sprague. There were earlier saleable installations of electric streetcars, including one in Berlin, as early as 1881 by Werner von Siemens and the company that still bears his name, and also one in Saint Petersburg, Russia, made-up and tested by Fyodor Pirotsky in 1880. Another was by John Joseph Wright, brother of the celebrated mining entrepreneur Whitaker Wright, in Toronto in 1883.The earlier installations, however, proved difficult and/or variable. Siemens' line, for example, provided power through a live rail and a return rail, like a model train setup, limiting the voltage that could be used, and providing unwanted stimulation to people and animals crossing the tracks. Siemens later planned his own method of current collection, this time from an overhead wire, called the bow collector. Once this had been developed his cars became equal to, if not superior than, any of Sprague's cars. The first electric interurban line connecting St. Catherine’s and Thorold, Ontario was operated in 1887, and was measured quite successful at the time. While this line proved quite versatile as one of the earliest fully functional electric streetcar installations, it still required horse-drawn carry while hiking the Niagara Escarpment and for two months of the winter when hydroelectricity was not available. This line continuous service in its original form well into the 1950s.