Rollover (key)

Rollover is the ability of a computer keyboard to correctly handle several simultaneous keystrokes.

Normal typing

During normal typing on a conventional computer keyboard, only one key is usually pressed at any given time, then released before the next key is pressed. However, this is not always the case. When using modifier keys such as Shift or Control, the user intentionally holds the modifier key(s) while pressing and releasing another key. Rapid typists may also sometimes inadvertently press a key before releasing the previous one. Certain unusual forms of keyboarding require multiple keys to be pressed or held down simultaneously; for example, Braille2000 keying requires as many as six keys to be pressed at once. Some computer games require keys (other than the usual modifier keys) to be held down while others are pressed and released.

n-key rollover

Certain high-end keyboards have "n-key rollover". This means that each key is scanned completely independently by the keyboard hardware, so that each keypress is correctly detected regardless of how many other keys are being pressed or held down at the time.

Keynote (presentation software)

Keynote is a presentation software application developed as a part of the iWork productivity suite by Apple Inc. Keynote 6.0 was announced on October 23, 2013 and is the most recent version for the Mac. On January 27, 2010, Apple announced a new version of Keynote for iPad with an all new touch interface.

History

Keynote began as a computer program for Apple CEO Steve Jobs to use in creating the presentations for Macworld Conference and Expo and other Apple keynote events. Prior to using Keynote, Jobs had used Concurrence, from Lighthouse Design, a similar product which ran on the NeXTSTEP and OpenStep platforms.

The program was first sold publicly as Keynote 1.0 in 2003, competing against existing presentation software, most notably Microsoft PowerPoint.

In 2005 Apple began selling Keynote 2.0 in conjunction with Pages, a new word processing and page layout application, in a software package called iWork. At the Macworld Conference & Expo 2006, Apple released iWork '06 with updated versions of Keynote 3.0 and Pages 2.0. In addition to official HD compatibility, Keynote 3 added new features, including group scaling, 3D charts, multi-column text boxes, auto bullets in any text field, image adjustments, and free form masking tools. In addition, Keynote features three-dimensional transitions, such as a rotating cube or a simple flip of the slide.

Database index

A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes are used to quickly locate data without having to search every row in a database table every time a database table is accessed. Indexes can be created using one or more columns of a database table, providing the basis for both rapid random lookups and efficient access of ordered records.

An index is a copy of select columns of data from a table that can be searched very efficiently that also includes a low-level disk block address or direct link to the complete row of data it was copied from. Some databases extend the power of indexing by letting developers create indices on functions or expressions. For example, an index could be created on upper(last_name), which would only store the upper case versions of the last_name field in the index. Another option sometimes supported is the use of partial indices, where index entries are created only for those records that satisfy some conditional expression. A further aspect of flexibility is to permit indexing on user-defined functions, as well as expressions formed from an assortment of built-in functions.

Chart

A chart, also called a graph, is a graphical representation of data, in which "the data is represented by symbols, such as bars in a bar chart, lines in a line chart, or slices in a pie chart". A chart can represent tabular numeric data, functions or some kinds of qualitative structure and provides different info.

The term "chart" as a graphical representation of data has multiple meanings:

Charts are often used to ease understanding of large quantities of data and the relationships between parts of the data. Charts can usually be read more quickly than the raw data that they are produced from. They are used in a wide variety of fields, and can be created by hand (often on graph paper) or by computer using a charting application. Certain types of charts are more useful for presenting a given data set than others. For example, data that presents percentages in different groups (such as "satisfied, not satisfied, unsure") are often displayed in a pie chart, but may be more easily understood when presented in a horizontal bar chart. On the other hand, data that represents numbers that change over a period of time (such as "annual revenue from 1990 to 2000") might be best shown as a line chart.