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Lab 2.3 Exercises

2.3.1. Identify Layers of User Interface Software

Implementing the user interface adds additional software layers to an interactive application.

a) Name the two layers that constitute the user interface. Discuss their significance and how they relate with other aspects of the system.

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A1:

Answer: User interface hardware and the user interface code. The hardware device provides the “interface” between human understandable components (pressing a key with a particular symbol, clicking a mouse button, images on the screen) and the computer system. When inputting information, the user performs certain actions with the interface devices and electric signals are generated, which are then passed to the user interface code. This code then translates the electric signals into so-called “events” to which the computer system can react. When sending information to the user, the software identifies certain events (e.g., the image on the screen has changed), the event is translated to electric impulses and then sent to the user.

b) How does the user interface code layer relate to the operating system?

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A2:

Answer: Usually the user interface code calls upon the code from the rest of the application, which in turn makes use of operating system services.

In essence, the operating system serves as the “middle man” between the different components. For example, you press a key on the keyboard, which sends information to the keyboard device driver, which may then be sent to the application or acted upon by the operating system. If intended for the application, the action may be something a simple as displaying the key on the screen (as in the case of pressing a letter in a word processing program). What the application needs to display on the screen is passed to the video driver, which sends the appropriate signals to the monitor. However, pressing a key may be something more complex like causing the application to print or saving the current document.
c) What kinds of software do not require much (if any) user interface?

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A3:

Answer: Software modules that drive network protocols, provide automation or control, and monitor access to databases, for example, do not interact with users directly and have little or no user interface code.

Although there are programs the utilize these other software modules, they are typically command-line oriented and therefore do not require much in the way of a user interface (other than meaningful and useful options). Granted, there are graphical tools to administer databases or configure your network. Once the installation and configuration are done, most of the work is done without user interference. Automation tools may also provide a graphical interface, but once they are set in motion, the work is done without the user's awareness.


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