Device Switching

Some time back, I was involved in a pro­ject that involved port­ing an AS/400 applic­a­tion to a web applic­a­tion. I volun­teered to be the usab­il­ity ana­lyst for the web applic­a­tion as I was involved in doc­u­ment­ing the AS/400 applic­a­tion and the devel­op­ment team did not ‘know’ the AS/400 applic­a­tion as much as I did. My tasks on the pro­ject included wire­frames on paper, Visio, and Acrobat, veri­fy­ing the HTML screens, and review­ing the usab­il­ity of the final applic­a­tion. I will try to blog about my exper­i­ences work­ing on the project.

Ini­tially I went about my tasks under­stand­ing AS/400 screens and ensur­ing they were recre­ated in the web applic­a­tion. Everything was fine on paper and screen. Noth­ing struck me as unto­ward. Only when I went back to the AS/400 doc­u­ment­a­tion, I real­ised that work­ing with the command-line inter­face was easier than the graph­ical inter­face. It was then I recalled a term called “device switch­ing”.

Device Switch­ing hap­pens when a user switches between using two input devices. mostly a mouse and a key­board. Marlin C. Brown in his book, Human-Computer Inter­face Design Guidelines, talks about this mouse-keyboard switching.

8.10 Mouse-Keyboard Switching

Avoid fre­quent mouse-keyboard switches.

Avoid requir­ing users to make fre­quent changes form key­board to mouse. In keyboard-intensive tasks, such as word pro­cessing, provide the neces­sary func­tions on the key­board (for example, cursor con­trol keys) to per­mit the user to per­form the task from the key­board. Fre­quent changes from key­board to mouse and back inter­fere with the flow, and thus the effi­ciency, of key­board tasks. The users must reori­ent their hands to the key­board after each mouse use.

Mouse & Key­board, via Flickr user: stopthegears

The AS/400 applic­a­tion has been in use for more than two dec­ades and that users have become pro­fi­cient in using the key­board. The AS/400 applic­a­tion, being a data entry intens­ive applic­a­tion and by vir­tue of its longev­ity, had ensured that users have a men­tal model of screens built into their minds and they have mem­or­ised the key sequences to use and nav­ig­ate through the system.

As a res­ult, I went back to the applic­a­tion and ensured that that tab­bing order was in the same sequence as that of the green screen. This took care of the issue of fre­quent device switch­ing asso­ci­ated with graph­ical interfaces.

The les­son I learnt from this was to test screens and forms for device switch­ing issues. The lower the num­ber of switches that occur, the bet­ter the usab­il­ity of that screen or form would be.