The discussion is bsed on two different perspectives. The explortion of the perspective of resercher of input/output devices who wishes to extend the design spce nd discuss n emerging prdigm of computer use, tsk-dependent computers, nd give some exmples of tht prdigm. Ultimtely, I will discuss the criticl role of input nd output devices, nd continue with the designer's perspective by discussing the motivtions for the evolution, the environments of use, nd the implictions of the environment on the interction technologies.
The mnner in which users interct with their computer is criticlly dependent on the choice of input nd output devices. This is such n obvious observtion tht sometimes system designers fil to tke it explicitly into ccount. ll interction with the computer consists of issuing commnd, providing dt on which the commnd will operte, nd, finlly, providing loction for the output of the commnd to be plced; this holds even when the execution of the commnd is temporlly disjoint from its invoction (e.g., scheduled opertion). The specifiction of those commnds involves specifying the commnd, the source of dt for the commnd, nd the trget for the output of the commnd. ll must be specified using vilble input nd output devices. Therefore, the choice of these devices will constrin the style of the interction possible for the user. (Bss et l., 2003:140)
Consider implementing windows-style interfce, without pointing device such s mouse. The windows style depends on the user being ble to point to the source nd destintion of commnd. (Spitzer et l., 1997:49) Furthermore, the type of pointing device is importnt. The precision of pointing is not s importnt s the speed of pointing. Thus, device such s trckbll is possible pointing input device tht dmits to gret precision. Not only does the trckbll dmit gret precision, but lso demnds it. Thus, the use of trckbll is conditioned on the bility to very precisely specify loction on the screen, to serve s the current loction. Becuse precise specifiction tkes time, lower precision, but inherently fster pointing device, such s the mouse, will llow much smoother interction with the computer. (Bss, Mnn, Siewiorek, Thompson, 2002)
The point of this discussion is tht there is coupling between the chrcteristics of n input or output device, nd the style nd mnner in which user cn operte computer. In this pper, we discuss environmentl nd tsk constrints on the choice of input nd output devices. It should be cler tht ny constrint on the devices my fundmentlly lter the type of interction tht the user hs with the computer.
In ny computer ppliction, distinction exists between input intended to control the computer (commnds) nd input intended to be retined (dt). The choice of pproprite input device will be hevily influenced by whether the device will be used primrily in the issunce of commnds or in the input of dt. In fct, the desktop hs seprte input devices for these two ctegories. The mouse is used primrily for commnds, wheres the keybord is used for the input of dt. The types of pplictions tht re primrily commnd oriented should not be discounted. ny dt retrievl ppliction (such s mny of those bsed on the World Wide Web) is primrily commnd oriented. (Normn, 2005) The commnds re used to nvigte to the desired dt item(s), nd then to specify how tht dt is to be displyed. In dt retrievl pplic