Anas Omar BaHammam

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Computer security is a branch of technology known as information security as applied to computer(s). The objective of computer security can include protection of information from theft or corruption, or the preservation of availability, as defined in the security policy.Computer security imposes requirements on computers that are different from most system requirements because they often take the form of constraints on what computers are not supposed to do. This makes computer security particularly challenging because it is hard enough just to make computer programs do everything they are designed to do correctly. Furthermore, negative requirements are deceptively complicated to satisfy and require exhaustive testing to verify, which is impractical for most computer programs. Computer security provides a technical strategy to convert negative requirements to positive enforceable rules. For this reason, computer security is often more technical and mathematical than some computer science fields.^{[clarification needed][citation needed]}Typical approaches to improving computer security (in approximate order of strength) can include the following:

• Physically limit access to computers to only those who will not compromise security.
• Hardware mechanisms that impose rules on computer programs, thus avoiding depending on computer programs for computer security.
• Operating system mechanisms that impose rules on programs to avoid trusting computer programs.
• Programming strategies to make computer programs dependable and resist subversion

The set of typewriter-like keys that enables you to enter data into a computer. Computer keyboards are similar to electric-typewriter keyboards but contain additional keys. The keys on computer keyboards are often classified as follows:

The standard layout of letters, numbers, and punctuation is known as a QWERTY keyboard because the first six keys on the top row of letters spell QWERTY. The QWERTY keyboard was designed in the 1800s for mechanical typewriters and was actually designed to slow typists down to avoid jamming the keys. Another keyboard design, which has letters positioned for speed typing, is the Dvorak keyboard.

There is no standard computer keyboard, although many manufacturers imitate the keyboards of PCs. There are actually three different PC keyboards: the original PC keyboard, with 84 keys; the AT keyboard, also with 84 keys; and the enhanced keyboard, with 101 keys. The three differ somewhat in the placement of function keys, the Control key, the Return key, and the Shift keys.

In addition to these keys, IBM keyboards contain the following keys: Page Up, Page Down, Home, End, Insert, Pause, Num Lock, Scroll Lock, Break, Caps Lock, Print Screen.

There are several different types of keyboards for the Apple Macintosh. All of them are called ADB keyboards because they connect to the Apple Desktop bus (ADB). The two main varieties of Macintosh keyboards are the standard keyboard and the extended keyboard, which has 15 additional special-function keys.

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