Home > Articles > Networking > Wireless/High Speed/Optical

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

Programming Considerations

Good application development means writing readable code. In fact, most developers consider writing readable code a professional responsibility. One of the ways to best improve the readability of your code is with white space.

White Space

The term white space refers to how text displays in contrast to the surrounding white space. For example, in reading this book, the text displays in a readable manner due to the use of indents, spaces, and paragraphs.

Using white space in programming provides the same results as it does for this book: It provides easier readability. Consider the following two WML code samples.

The first example does not use white space, but the second example does. Which would you, as a developer, rather interpret if trying to understand this code?

An example of WML code without white space:

<wml><card><p>Sample text</p></card><wml>

An example of WML code with white space:

   <p>Sample text</p>

Notice the difference in appearance. Although not required, it's usually good practice to incorporate white space into your code. Readable code not only aids you in reducing and debugging errors quickly, but it also aids others who might need to read and understand your application's code at a later date.


WML ignores white space when actually compiling the code. To control the way text displays on a device, you must use text-formatting tags (you'll learn more about this in Chapter 4, "Text Formatting for WML").


Another way for developers to produce readable code is to incorporate comments. Developers often use comments to leave notes about their application logic. This practice is especially useful when needing to update a portion of code or when another individual needs to edit your code.

To add comments within WML, you must use the <!-- symbol before the comment. The --> symbol is then used to end the comment. Comments are solely for the use of developers—they never display on the application.

The following example displays the use of comments within a WML file. WAP device compilers do not interpret or read comments:

<!-- This is a comment line -->
   <p>Sample text</p>

In this example, the comment displays across only one line. You can, however, extend a comment across multiple lines. Until you end the comment with the --> symbol, the device compiler assumes that all information after the starting <!-- tag is a comment. The following is an example of code using a comment that extends across multiple lines:

<!-- This is also
a comment line -->
   <p>Sample text</p>


Be sure you do not include any space within the starting and ending comment tags. For example, the following starting comment tag would produce an error when trying to run your code:

< ! --

The reason this tag is incorrect is because it contains spaces. The same is true for the ending comment tag. The following ending comment tag is also incorrect:

-- >

The most common error with comment tags occurs when developers place a space somewhere within a comment tag.

WML Elements: The Building Blocks of WAP Applications

In the world of WAP development, applications use things called elements. In the following pages, you begin your development efforts using the WML elements required for all WAP applications within this book.

Elements are the heart of markup languages, including WML. They designate functional and structural information used within a WML deck. All WML elements have one of the following structures:

  • A start tag, some content, and an end tag. Here's an example:

  • <tag>content</tag>

  • A tag that contains no content is called an empty-element tag. These tags contain neither a start nor ending tag, such as


In this chapter, you'll learn most of the WML that makes up WML decks and cards (you'll look at the TEMPLATE element, another WML deck-level element, in Chapter 5, "Navigation Using WML"). Table 3.2 summarizes the WML elements discussed in this chapter.

Table 3.2 The WML Deck/Card Elements





Starts and ends a deck and encloses all cards.



A single WML unit, which can contain-information such as text to present to the user, instructions for gathering user input, and so on. WML cards are to a WAP application as pages are to a Web site, or screens are to PC applications.



Specifies deck-level actions that apply to all cards in the deck.



Contains information relating to the deck as a whole, including metadata and access control elements.


There are a few factors to remember when working with WML elements. First, all WML tags must be lowercase. Looking at Table 3.2, a WAP application would not recognize the <CARD> tag because it is uppercase. However, a WAP application would recognize the <card> tag because it is all lowercase.


Just because WML tags must be lowercase does not mean that the content within the tags must be lowercase. For example, consider the P element, which defines text within a WAP application (the P element is discussed in the next chapter). Although the <p> tags must be lowercase, the content between the tags can contain both upper- and lowercase characters:


WML tags must also be enclosed in angle brackets (< >). WML elements also must have a starting tag (such as <card>) and an ending tag (such as </card>). Ending tags contain a slash character to identify them as end tags.

WML Attributes

Some WML elements use settings (called attributes) to further define an element. For example, some attributes identify pointers that refer to areas outside a WML card; other attributes might label information that has to be communicated back to a Web server. Still, other attributes might label the code that specifies how to display an onscreen object.

Some attributes are mandatory, whereas others are optional. You'll look at the attributes available with each WML element as we come to them.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020