Chapter 12

Human /Computer Interface

• User Friendly- Easy to learn and use-

must be defined in terms of the users,novice or expert

Users Change:Build interfaces with critical elements

that change as the users become more experienced.

1. Experience with computer systems.

2. Type of work a person is doing and how the computer assists them.+ perform faster, fewer errors, greater satisfaction.

3. Enthusiasm level of potential users.

4. Age

Acceptance Factors

Worst Case Scenario- Person with no experience, who works in sales, thinks learning the computer is a waste of time, nearing retirement (60’s).

Number of User Interfaces

Ex. Automatic Teller Machine1. Customers2. People who load the money3. People who do software repairs4. People who do hardware repairs

ConsistencyFrom display to display,

From message to message,

From program to program,

Within the same system.

Ex. Microsoft office

Adequate Feedback

Current system status

Options available

User action> computer reaction

Possible next step

Improving User Accuracy and Facilitating Error Handling

Reduce the opportunity for errors, increase the detection of errors, provide opportunity to correct errors.

Input Methods

1. Alphabetic KeyboardsOver 100 years- qwerty*Left hand-56% of total strokes*Reach from home row for 68% of key strokes (possible to stay on home row 70% of the time)

2. Mouse, touch panel, speech recognition, etc,

Types of Languages

Command- Special languages developed for a particular system.

Quasi-Natural- Designers allow the use of two or more words to describe a particular action.

Natural Language- users input to the computer those words that come to mind.

Interactive Procedures

Procedures relates to a series of actions or transactions that are carried out to accomplish some objective.

Transactions are a single exchange between the human and the computer.

Procedures should be natural and efficient.Natural – Fits neatly into user’s

expectations.Efficient- Minimizes the time.

Procedure decisions for efficient data entry:

1. User should not enter the same data twice.

2. Users should not enter data the computer already has or can generate.

3. Users should not reenter a series of data items to correct the info in a single data item.

4. The order of entering data items should be consistent with the source document.

Table 12-1 Proposed Commands for Ending an Interactive Session

Command Percent ofName TotalEnd 35Quit 19Exit 13Finished 10Cancel 3Clear 3Complete 3Done 3Home 3Leave 3Stop 3All others 2Total 100%

From Carter, 1986.

Human/Computer Dialogs:

Question/answerMenuForm fillingDirect manipulationCommand drivenInteractive graphicsQuery languages

User Guidance Asking others preferred way

Help facilities context sensitive

Computer-based documentationmore detailed info than the help facility.

Computer-based trainingone or more training modules embedded in the system.

short tutorial exercises where computer checks answers

Figure 12-26The most commonly used screen-based

controls in graphical user interfaces.

Menu itemsPushbuttonsOpen selection listsDrop-down selection listsCombination drop-down selection listsCombination open listsText entry FieldsCheck boxesRadio buttonsSpin listsCombo spin listsSlidersNotebookPaletteValue Set

Figure 12-27 Example of a menu bar and pull-down menu showing menu items.

Bailey Automated Grocery System-Grocery Items

Grocery Items View Edit Details Window HelpSelected

CutCopyCreatePastePrint…ClearDeleteSelected Help

Open As

OK

Cancel

Help

Connect…

Add >>

Setup…

a. b. c. e. OK

X Cancel

Cancel

Ok

7 8 9

4 5

1 2

6

3

9593 9492 96

Jan FebMarAprMayJun

AugJul DecNovOctSep

Figure 12-29 More Examples of pushbuttons

Today

September 1994

S M T W T F S2

85 7

1

6

3

1094

13

1918

16151211

25 26

14

2928

22

27

20

30

23 2421

17

Check Box

Definition: A control used to display a choice that has two clearly distinguishable states, such as “on” or “off.”

Check boxes can be used individually or in a group to provide users with multiple choices. An example is shown in Figure 12-34.

Check Box

Wrap TitleOptions

Auto Arrange

Save Settings

Minimize on Use

X

X

X

X Bold

Italic

Underline X

X

Auto Deselect

Hot Keys

Disable start-upRight

Left

Top

Bottom

Figure 12-34 Examples of Check Boxes

Typical Uses of Check Boxes

Use individually, when choices only need to be set to “on” or “off,” “yes” or “no,” and so on.

Use as a set (group) when choices are not mutually exclusive.

Guidelines for Check Boxes1. Assign a mnemonic to each check box choice.

2. Capitalize the first letter of only the first word of a label (unless the item contains another word that would normally be capitalized).

3. Capitalize the first letter of all major words in the choices.

4. Avoid using check boxes (check marks) in menus.

5. Use instead of two radio buttons if the choice can only be set to “on” or “off”.

6. If all the objects or data items have that property turned on, display a mark in the check box.

7. If some, but not all, of the selected objects or data items have that property turned on, fill the box with shading.

Entry FieldDefinition: A control into which users type one or more text

characters. The entry field can contain one or more lines. Also known as the text entry field, text field, text region, or text box. An example is shown in Figure 12-35.

Command

Name: ________________________Street: ________________________City: _________________ State: ____

Customer

Fax Send

Number:

Name:

Recipient

Find:Jones

Smith

Replace With:

Figure 12-35 Examples of entry fields

Tree OnlyDirectory Only

ViewTree and Directory

Sort by Name Sort by Type Sort by Size Sort by Date

Setups Patch Maps Key Maps

Top

Bottom

Left

Right

GravityNone

Auto Test

Snap

Arrange

Field Alignment

Left

Right

Center

Justified

Figure 12-36 Examples of radio buttons

Spin Lists

Definition:A control used to display in sequence a

series of items, such as days of the week. Users press a small pushbutton to cycle through the options and find the desired selection. Some spin lists are combo spin lists that allow users to either spin through the options or type into entry field. An example is shown in Figure 12-37.

March Friday

9: : 56 PM

Month Day of Week

Time35

Date/28/949

3

Border Width

75 Pixels

Spacing

30

Delay

Minutes

X1

X1

L

R

Gain

Figure 12-37 Examples of spin lists

Typical use of Spin Lists

When potential selections have logical consecutive order

Guidelines for Spin Lists1. Pressing the up arrow button should

cause the display to increase or move forward, for example, from 14 to 15, from Friday to Saturday, or from low to medium.

2. Pressing the down-arrow button should cause the display to decrease or move back, for example, from 12 to 11, from August to July, or from high to moderate.

3. Allow users to spin through the entire list and back to the beginning by pressing only the up-arrow or down-arrow buttons.

Slider

Definition: A control used for making qualitative settings. Examples are shown in figures 12-38.

Slow Fast

Double-Click Speed

Figure 12-38 Example of sliders

Typical Use

When users can benefit from viewing the current value relative to the range of all possible values

Spacing

0X Offset

0 Y Offset

70

60

X Space

Y Space

Figure 12-39 More examples of sliders

Vol

Master Control

TrebleBass

Complex Screen-based Controls

There is a growing number of complex screen-based controls. They usually have more than one component and are used in special-purpose situations. Some of these screen-based controls are discussed next.

Notebook

Definition:A control resembling a bound notebook that contains pages separated into sections by tabbed divider pages. The tabs enable users to quickly move from one section to another. Arrow buttons enable users to turn pages of the notebook.

Typical Uses of Notebooks

When information has only one level of organization (e.g. an alphabetized index or address book)

When data can be logically organized into groups

When dealing with information that users would expect to find in notebooks in real life

Line Width

Figure 12-42 Examples of palettes

Fill Pattern

Basic Colors

Value Set

Definition:A control that allows users to activate

one choice from a group of mutually exclusive choices. An example is shown in Figure 12-43.

abc

Figure 12-43 Examples of value sets

Typical Uses of Value Sets

When selecting from a set of graphical representations that are mutually exclusive

When selecting from a set of short textual choices that are mutually exclusive

Guidelines for Value Sets1. Provide at least two choices.

2. Choices can be provided as radio buttons, graphics, or pushbuttons that are grouped together.

3. If choices are displayed as a group of pushbuttons, locate the pushbuttons so that the edges touch (do not overlap).

4. Capitalize the first letter of only the first word of a label for a value set choice (unless the choice contains another word that normally would be capitalized).

5. If a choice is currently unavailable, display it with unavailable emphasis.

6. Assign one choice as the default choice.

7. If choices are text, assign a mnemonic to each choice.

Comparing the Performance of Screen-based Controls

Relatively few published studies provide head-to-head comparisons of even the most used screen-based controls. Two studies have compared the effectiveness of text entry and selection methods for entering dates (Gould et al., 1989) and making airline reservations (Greene et al., 1992). Both studies found text entry methods faster and preferred over selection methods.