Art Letzler

CSIS 672 – Homework Assignment # 1

(This report is my own work, but I received assistance from Dr. Manaris in figuring out how to create the alarm sound and how to approach the use of the analog alarm hand in resetting the alarm time.)


The purpose of this document is to describe the human computer interfaces associated with the Visual Basic Analog Alarm Clock application included with this submission.


Figure 1 is illustrates the basic Desktop Clock interface as appears when the application is first invoked.



Figure 1



The left hand side of the window presents the analog clock face.  The controls are contained on the right side of the window.  The following controls are provided for the clock:


·         The Alarm On / Alarm Off radio buttons in the upper right hand corner of the clock activate and deactivate the alarm functions.  As illustrated, the alarm function is deactivated when the clock is initiated (the Alarm Off  button is activated).  The alarm function is not active in this state.  The Alarm On button is selected to activate the alarm function.  These buttons serve as both the activation controls and the status indicators for the alarm function.


·         The Alarm Set command button below the radio buttons provides access to the controls which set the time for the alarm to sound.  When this button is clicked, the controls to set the Alarm Hour and the Alarm Minute are revealed.  The alarm times may be set either by entering the appropriate values in the appropriate box or by using the drop down list provided.  The Alarm Minute drop down list allows the user to select alarm times at 5 minute intervals, and the alarm may be set at l minute intervals through direct text entry.  The Alarm Set button also provides access Alarm Time field which displays the time at which the alarm will ring (assuming that the alarm is active). 


·         The Snooze button is enabled only when the alarm is ringing.  When it is clicked while the alarm is ringing, the alarm stops sounding and the alarm time is reset for 10 minutes in the future


Figure 2 illustrates the Desktop Clock interface with the Alarm On button selected, and the Alarm Set controls revealed. 





            Figure 2



Figure 3 illustrates the appearance of the Desktop Clock interface with the alarm sounding.  Note the large sun icon which flashes on and off as a visual indication that the alarm is ringing.





            Figure 3


Usability Analysis


The Desktop Clock is modeled on the traditional analog wall clock and the controls typically found on a standard  bedroom alarm clock (analog or digital).   An analysis of the usability of the Desktop Clock interface is presented below in the context of Norman’s usability analysis concepts. 


            Affordances / Constraints


The interface design incorporates affordances and constraints which guide the interaction and encourage the appropriate response.  For example, the Snooze button affords clicking, but it doesn’t do anything except when the alarm is ringing.  As a result, an inadvertent clicking of the Snooze button cannot set the alarm time.  The Alarm On button and the Alarm Off button afford clicking to activate / deactivate the alarm function.  The interface design ensures that both of these buttons are not activated at the same time.  When the alarm stops ringing after 5 minutes, the alarm function is reset to Alarm Off; it may be restored by clicking the Alarm On button.


Conceptual Model


Usability and learnability are significantly facilitated by maintaining consistency with the wall clock and alarm clock models.  For example, hour and minute hands are both the same color, but the hour hand is shorter consistent with the familiar wall clock standard.  The second hand and the Alarm Hand are in contrasting colors.  The green color of the Alarm Hand is based on the “green implies go” metaphor consistent with the idea that when the alarm rings, it is time to get moving.  The Snooze button operates in exactly the same way as the “Snooze” button on the top of most bedroom alarm clocks.


While the alarm time setting mechanism is not entirely consistent with the mechanism used in most bedroom alarm clocks, it improves on the familiar mechanism by applying standard features of the windows interface model.  The windows interface model is, of course, very familiar to users of the desktop on which the clock is designed to operate.  Note that the sizing of the overall Desktop Clock also follows the Windows model, and the clock may be resized by dragging the edges of the Window.


The Alarm Time may also be set by dragging the Alarm Hand in an analog fashion as a complement to the digit Alarm Set controls revealed by the Alarm Set button.  This action takes place in the same by grabbing the Alarm Hand with the Mouse and moving it in the same fashion that the Alarm Hand may be used to set the Alarm Time on an analog wall clock.




Visibility of both the output display and the controls is very good.  The analog clock display is large and uses contrasting colors to facilitate the identification of the individual hands.  In addition, the hands are of different lengths and the shorter hand is always displayed on top of the longer hand.  In addition, the controls are well labeled are clearly visible and well labeled.  The controls to set the alarm time can be hidden when they are not in use so that they do not clutter the display with extraneous and potentially confusing information. 




The mapping between the available functions and the associated controls is generally intuitive and consistent with the bedroom alarm clock model and, to a lesser extent, standard windows desktop controls.  For example, the Alarm Set button reveals the well labeled controls to set the Alarm Hour and Alarm Minute.  The display of the Alarm Time below the Alarm Set controls is a redundant confirmation that the obvious mapping is correct.




Feedback is provided to confirm all actions taken on the available controls.   This feedback is both visible and instant for all of the controls.  For example, when the Alarm Set button is clicked, the alarm set controls either appear or disappear immediately.  When the Alarm Hour or Alarm Minute is changed, the Alarm Time is immediately updated and the alarm hand on the face of the clock is repositioned to reflect the updated alarm time.  When the Snooze button is hit (clicked), the alarm (sound and image) immediately ceases and the Alarm Time (which may or may not be visible) is updated.  (The alarm hand also moves but this movement is very small and may not be perceptible.)