The CLI has been in use since the early days of computing, when it became possible to enter commands the computer could obey from a keyboard, instead of having to use cards or paper tape punched with holes representing the codes a computer could understand as the commands it needed to perform the task at hand. The CLI allowed a higher level of abstraction for interfacing with the computer, as English like commands could be used to instruct the computer as to what needed to be done. These commands came complete with their own syntax and semantics, and constituted the command language that was taken by the CLI and translated into the machine code the computer needed to complete it's job. The learning curve associated with becoming familiar with this language was often a steep one, and appeared overwhelmingly daunting to the neophyte computer user. Once learned, however, by simply typing in a few commands, the computer user can get the computer to rather quickly do whatever it is capable of doing. As research continues and CLI's get more powerful, the command language becomes more English like and intuitive to the casual computer user.
GUI's, on the other hand, are a relatively recent arrival on the computer scene. Developed at Xerox's Palo Alto Research Center (PARC), they were originally called the Star Interface, after the computer system they were developed for. With this type of interface, instead of typing in commands from the computer keyboard, the user picks from among a screenful of graphical images, called icons, to direct the computer about it's job. The icons have been designed to be intuitively obvious as to which function they perform. Also present on the computer screen are a series of commands, called a menu, that can be selected individually to do other jobs. All of this selection is done with an input device called a mouse, which moves an arrow like pointer around the screen, and when the pointer is overlayed on the menu item or icon desired, a button on the mouse is pushed to select, or "click on" the item. This allows access to the functions and applications of the computer without the user needing to be a keyboard wizard, or to even fully understand the workings and capabilities of the computer. The intuitiveness of the icons is what is supposed to make the use of the computer easy and straightforward.
This is the main dichotomy of the interfaces then, the use of words typed in from the keyboard, or the use of pictures that can be clicked on. Which one is easier and more productive for both the neophyte and the experienced computer user become the arguable points that are so hightly subjective, these concepts of initial intimidation and the latter ease of use in an intuitive way that is not frustratingly bulky and slow.
CLI's assume at least a smattering of knowledge of both computer systems and the command language in use on the particular computer used. On the road to becoming proficient, technical manuals and tutorials on the computer and its application programs will quickly expand to fill all available shelfs and file storage space. Once learned, however, the user can get directly and quickly to the function or reference material needed. (This also presupposes oganization on the part of the user, a weak premise at best.)
Computers which use GUI's are sometimes conspicuous by the absence of paper documentation scattered everywhere. The menu and icon structure is always on the screen, and new users can just start clicking away (usually on the "HELP" menu item) to accomplish what they want. GUI's try to present everything to the user in a graphical way, and almost all of the reference material and tutorials are in an electronically storable form, or on disk. Since disk storage space is still at a premium on most systems, help material tends to be terse, and often incomplete, leaving the user to fumble through the menu structure. Also, experienced users sometimes report being frustrated with the feeling of "you can't get there from here" as they navigate multiple layers of the menu system to do what they want. The menu and icon stucture leads the user by the hand at all times, so the need to know any of the underlying concepts and relationships of the computer system is unnecessary. This is attractive to those computer users who don't, can't or won't take the time to learn all the features and efficient use of the resources to which they could avail themselves. This use of GUI's and the type of person they appeal to is also the cause of some debate.
One study, reported in the magazine "Computers in Education", states GUI's may contribute to a loss of cognitive skills. Based on an analysis of essay assignments in a college english class, it appeared that students who used CLI type computer systems, and therefore had to be aware of syntax, semantics, and the logical flow of the thought processes that lead to a problems solution, wrote higher quality, more logically correct and connected papers. Users of GUI's, who didn't have to think, had a tendency to write in incomplete sentences, many of which were not logically connected. This was attributed to atrophy of the higher brain functions. The alternative is that GUI's naturally attract people who think like that, of which there seem to be quite a few, hence the popularity of GUI's.
The final decision as to which man-machine interface is better comes down to a personal choice. Which one is most comfortable, and can be learned in the alloted time, combined with the nature of the user's need for a computer. It may turn out that the best is a combination of the two, and only by becoming familiar with both may an intelligent decision be made.
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