ASP Nut Glossary

The ASP Nut glossary contains terms that are commonly used when discussing Active Server Pages and its related technologies.

ADODB

This is a code library which enables you to access a database from your ASP code. You talk to the database using an ADODB.Connection and you return results from the database using an ADODB.Recordset.

COM+ Object

The COM+ Object is a compiled module (DLL) which may be installed on your web server and accessed by using the Server.CreateObject construct. You may create COM+ objects using any of Microsofts development languages including Visual Basic and Visual C++. This type of object is also (formally) known as an ActiveX DLL.

Connection Pooling

When your web site application is running, the number of simultaneous database connections your site requires will vary. IIS maintains a pool or array of active connections regardless of the activity of your site. This ensurs that whenever your load increases, the connections will be ready to use. This increases the performance of your web site.

Connection Sharing

A feature built into IIS that allows your ASP scripts to share the same database connection. Since creating and destroying database connections is costly (in terms of performance), this is a huge performance boost. You don't need to write any special code to take advantage of this feature, IIS will implement this for you.

Enumeration

The process of iterating over all of the possible keys for a hash table or elements for an array. This is done using the ASP statement For Each as shown below:

' iterate over all of the session variables
Dim sKey
For Each sKey In Session.Contents
	Response.Write sKey & " = " & Session(sKey)
	Response.Write "<BR>"
Next

Event Handlers

Event Handlers are special subroutines that are executed when special events happen on the web server. Visual Basic programmers should be very familiar with these special functions. There are only four different event handlers for ASP which must be defined in your global.asa file.

Application_OnStart
Application_OnEnd
Session_OnStart
Session_OnEnd

Hash Table

A hash table is a string-to-value relationship that is similar to an array. Instead of using a numeric index to individual elements, we use a string "key" that maps to a "value". The Application and Session objects store hash values.

If you want to create a hash table in your ASP code, you can do so by creating an object using the following code:

Set oHash = Server.CreateObject("Scripting.Dictionary")

Hungarian Notation

A naming convention where you prefix a variable name with one or more character which indicate the type of value that is stored inside. Since all variables are of "variant" type in ASP, your notation should define what "sub-type" the variant should hold.

Internet Information Server (IIS)

IIS is the main web server application that runs on Microsoft Windows™. It is included free with Windows XP Professional™ and Windows 2000 Professional™ as well as all of the server operating system software produced by Microsoft.

The ASP scripting language is built-in to the server software and no configuration is necessary to run ASP scripts on this web server.

Intrinsic Objects

Microsoft IIS web server comes with several "built-in" or intrinsic objects to make your life easier. This includes the Request object for processing form values, querystring variables and cookies; the Response object for setting cookies and performing redirects; the Session object for managing user-specific data.

Naming Convention

A standard practice of naming your variables, functions, subroutines and class names. The naming convention should help you to differentiate between the different types of objects in Active Server Pages. You may also use a naming convention to define your ASP script filenames.

Object-Oriented Programming (OOP)

Object-oriented programming is a programming language feature which allows you to think of theoretical contstucts as objects. These objects can protect data, abstract complex processes and inherit features from one another.

ASP scripting supports a very limitted subset of these features with the introduction of IIS 5.0. You have the ability to define your own classes using ASP scripting.

OLEDB

This is data-access provider that is used to communicate with a database through ASP scripting. OLEDB is the fastest and most efficient way of communicating with a database under Microsoft Windows™. It bypasses ODBC in order to eliminate the overhead it adds which reduces performance.

Pass by Reference

One of the ways to pass data (variables) to a function or subroutine in ASP. This is the default method of handling arguments and tells the function to use a reference so that when the variable changes value, the original argument will be changed as well.

You may explicitly declare a parameter as Pass by Reference by using the ByRef keyword.

Pass by Value

One of the ways to pass data (variables) to a function or subroutine in ASP. This tells the function to use a copy of the argument value so that when the variable changes value within the function, the original argument will remain unchanged.

You must explicitly declare your parameters as Pass by Value by using the ByVal keyword.

Primitive Values

Primitive values are the atomic data types which cannot be "broken down" into smaller components. All variables sub-types with the exception of arrays and objects are primitive values.

Redirect

Sometimes referred to as an HTTP Redirect. A Redirect is a special header that instructs the client to immediately go to another web page and not continue loading the current page. This is often used in ASP when a certain condition is or is not met and you want to make a decision to show one page or another. Redirects are done in ASP code by using the Response.Redirect statement.

Self-Documenting Code

A coding methodology which decrees that code should be written in a manner such that it documents itself (doesn't require commenting.) This is accomplished by using descriptive variable and funcion names and clearly arranged conditional statements.

Server-Side Includes (SSI)

A server-side include is a web server directive that is evaluated by the server when a user requests a page. This directive includes HTML or ASP code from another page and inserts it where the directive is placed. The include looks like the following:

<!-- #include virtual="/include/my_lib.asp" -->

Includes may be "virtual" meaning that the file is found based off the web site root or non-virtual using the "file" attribute which locates the file relative to the directory of the current script (with the include directive.)

Session State

If you have the session object enabled on your web server (IIS) then you can track the session state. The session state is the current status of each visitor to your site. You may associate as much information as you need about the visitor by making use of the session hash. Each unique visitor has its own copy of the session object.

The session object may be used to track user preferences or maintain a shopping cart. Virtually any information you want to associate with your web site visitors can be saved in the session. Be aware that the session will timeout after 20 minutes or however long you have configured your sessions for.

Variant

The default data-type used by Active Server Pages. All variables use this major variable type and ASP will not even allow you to declare types. A variant can hold may different "sub-types" of values including strings, numbers, dates, booleans, and objects.