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Programming is all about doing stuff to things. Generally, the stuff is the execution of a process or algorithm and the things are information or data.

An algorithm is just a fancy name for a series of steps, like tying your shoelaces. Information or data is just values. Your name is a piece of information and so is your birth date. Since it's shorter, in this chapter we'll use the word data to describe a piece of information.

In ColdFusion, data is held in variables. Think of a variable like a mailbox. You can stuff things like letters and packages into a mailbox and get them out later to do stuff. ColdFusion makes storing information very easy because it's a loosely typed Language. You can stick any kind of data into a ColdFusion variable without having to tell ColdFusion what kind of data it is.

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In our last Section, we talked about variables, data, and how to transport data around in your application. Different data types serve different purposes.

Strings/Numbers

Is Simple: Yes

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In our previous sections we talked about the importance of adding context into your programs. You’ll find you will spend much more time reading programs for the purposes of debugging and enhancing, than you spend writing the program. So take care to write your programs in such a way the program can be read and understood as easily as possible.

Context is important because our programs express a problem to a computer using a kind of shorthand, in our case ColdFusion programming code. The computer doesn’t much care about the amount of context in the application, as long as the instructions (code) are all properly formed. The program is good enough for the computer if it works well. But this doesn’t necessarily mean the program is good enough for a human. Programs that are good for humans can be efficiently understood, debugged and enhanced by another programer.

One way to add context is to use descriptive variable names.

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ColdFusion has been designed to allow the use of ColdFusion tags and ColdFusion script. Functionally, both will be interpreted equally and will achieve the same result. The use of ColdFusion Tags and ColdFusion Script is up to personal or team preference. One or two ColdFusion operations are currently Tag only, as of this tutorial, but these will be made available in ColdFusion script in future releases.

Some developers write all ColdFusion code in Tags. Some developers write all ColdFusion code in Script. Some write the view portions of their ColdFusion code in Tags and the business layer portion in Script. As long as you stay consistent, all approaches are valid. The overarching rule should be legibility and consistency.

Let's look at some statements and compare the differences:

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In the first part of this hands on we are going to convert some pages to .cfm pages. We will then add some variables and output them to the user. Finally, we will add a comment to our code.

Tags Used: <cfset>, <cfoutput>

1. Rename the /www/index.html file to index.cfm.

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In this section of the hands on we will switch from tag based code to script based code and create a structure of data. We will then output that on the page.

Tags Used: <cfscript>, <cfoutput>

1. Open up the /www/about.cfm file in your code editor.

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An important part of any program is the ability to make decisions based upon a set of conditions. This is aptly named 'conditional logic'. Unless you are writing a static set of HTML pages, you will almost certainly need to evaluate conditions. In conditional logic, all conditions tested must evaluate to a Boolean, either true or false. As you learned in the variables section of this training, ColdFusion is a dynamically typed language. This does not mean that ColdFusion is not typed, but rather that ColdFusion can switch from type to type dynamically while the application is executing. This is a great feature when using conditional logic as you do not need to explicitly define the Boolean such as myVar == true, but for simple variables you can allow ColdFusion to evaluate the value of the variable and convert it dynamically to a Boolean value. Keep this in mind, and we will revisit this in a bit.

ColdFusion has both if/then/else tags

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ColdFusion groups variables together in scopes, or a range in which a variable can be accessed. Think of a scope as a bucket of memory that can store variables. Each scope has its own purpose, and each scope has its own lifecycle.

The following table shows major scopes available in a running ColdFusion application:

• Variables: Default scope available in ColdFusion templates. Variables are available only during the execution of the template.

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In this hands on, we are going to refactor our code and take out any unnecessary logic we might have.

Tags Used: <cfif>, <cfelse>

1. Open up the /www/contact.cfm file in your code editor and locate the <cfif> statement that checks the form.contactname variable. Remove the eq 0 part of the expression; as any number greater than 0 is treated as true, and the number 0 is treated as false, we do not need this additional part of the <cfif> statement. Because we only want to run the code when there is NO value passed we must negate the value by putting the word NOT before

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In this hands on, you are going to update our code to provide a better user experience to your users as well as improve the form validation.

Tags Used: <cfparam>, <cfoutout>

Functions Used: len, trim