Encyclopedia of Computer Science and Technology

ergonomics of computing 185consisting of 0, 1, 2, 3, . . . and their negative counterparts.Pascal also includes built-in functions to retrieve the precedingvalue in the enumeration (pred), the following element(succ), or the numeric position of the current element(ord).The main advantage of using explicit enumerations isthat a constant such as “Monday” is more understandableto the program’s reader than the value 0. Enumerations arefrequently used in C and C++ to specify a limited groupof items such as flags indicating the state of device or fileoperation.Unlike most other languages Pascal and Ada also allowfor the definition of a subrange, which is a sequential portionof a previously defined enumeration. For example, oncethe Day type has been defined, an Ada program can definesubranges such as:subtype Weekdays is Days range Monday . .Friday;subtype Weekend is Days range Saturday . .Sunday;SetsThe set type (found only in Pascal and Ada) is similar to anenumeration except the order of the items is not significant.It is useful for checking to see whether the item being consideredbelongs to a defined group. For example, instead ofa program checking whether a character is a vowel as follows:if (char = ‘a’) or (char = ‘e’) or (char = ‘i’)or (char = ‘o’) or (char = ‘u’) . . .the program can define:type Vowels = (a, e, i, o, u);if char in Vowels . . .Further ReadingSebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Pearson, 2007.ergonomics of computingErgonomics is the study of the “fit” between people andtheir working environment. Because computers are sucha significant part of the working life of so many people,finding ways for people to maximize efficiency and reducehealth risks associated with computer use is increasinglyimportant.Since the user will be looking at the computer monitorfor hours on end, it is important that the display be largeenough to be comfortably readable and that there be enoughcontrast. Glare on the monitor surface should be avoided.It is recommended that the monitor be placed so that thetop line of text is slightly below eye level. A distance ofabout 18 inches to two feet (roughly arm’s length) is recommended.There has been concern about the health effects ofelectromagnetic radiation generated by monitors. Most newmonitors are designed to have lower emissions.While the “standard” keyboard has changed little in20 years of desktop computing, there have been attemptsat innovation. One, the Dvorak keyboard, uses an alternativearrangement of letters to the standard “QWERTY.”Although it is a more logical arrangement from the point ofview of character frequency, studies have generally failedto show sufficient advantage that would compensate forthe effort of retraining millions of typists. There have alsobeen specially shaped “ergonomic” keyboards that attemptto bring the keys into a more natural relationship with thehand (see keyboard).The use of a padded wrist rest remains controversial.While some experts believe it may reduce strain on the armand neck, others believe it can contribute to Carpal TunnelSyndrome. This injury, one of the most serious repetitivestress injuries (RSIs), is caused by compression of a nervewithin the wrist and hand.Because of reliance on the mouse in many applications,experts suggest selecting a mouse that comfortably fits thehand, with the buttons falling “naturally” under the fingers.When moving the mouse, the forearm, wrist, and fingersshould be kept straight (that is, in line with the mouse).Some people may prefer the use of an alternative pointingdevice (such as trackball or “stub” within the keyboarditself, often found in laptop computers).A variety of so-called ergonomic chairs of varying qualityare available. Such a chair can be a good investment inworker safety and productivity, but for best results the chairmust be selected and adjusted after a careful analysis ofthe individual’s body proportions, the configuration of theworkstation, and the type of applications being used. Ingeneral, a good ergonomic chair should have an adjustableseat and backrest and feel stable rather than rickety.The operating system and software in use are alsoimportant. Providing clear, legible text, icons or othercontrols and a consistent interface will contribute to theuser’s overall sense of comfort, as well as reducing eyestrain.It is also important to try to eliminate unnecessaryrepetitive motion. For example, it is helpful to provideshortcut key combinations that can be used instead of aseries of mouse movements. Beyond specific devices, thedevelopment of an integrated design that reduces stressand improves usability is part of what is sometimes calledhuman factors research.In March 2001, President Bush cancelled new OSHAstandards that would have further emphasized reportingand mitigating repetitive stress and musculo-skeletal disorders(MSDs). However, the legal and regulatory climateis likely to continue to place pressure on employers to takeergonomic considerations into account.Further ReadingCoe, Marlana. Human Factors for Technical Communicators. NewYork: Wiley, 1996.Dul, Jan, and Bernard Weerdmeester. Ergonomics for Beginners:A Quick Reference Guide. 2nd ed. Grand Rapids, Mich.: CRCPress, 2001.“Ergonomic Design for Computer Workstations.” Available online.URL: http://www.ergoindemand.com/computer-workstationergonomics.htm.Accessed July 30, 2007.