Have you ever wanted to create a command alias that represented a specific option of a command? Or maybe you have established CAD standards, but some of the settings can't be set up through a drawing template alone. So you want to make sure the settings are finished before any work on a design begins? If so, you have come to the right place. AutoCAD is more than just a drafting tool. Although customizing AutoCAD can help increase productivity by itself, the programming interfaces allow you to tap into much more powerful resources that are contained in the depths of AutoCAD. (Okay, saying the resources are in the depths of AutoCAD might be a bit of an exaggeration since they are used every time you run a command in the AutoCAD interface.)

AUTOCAD LT

This minibook is aimed at AutoCAD users only. Sorry, AutoCAD LT users - the programming interfaces are limited to AutoCAD.

The supported application programming interfaces (APIs) for AutoCAD are available after you install AutoCAD or after you've downloaded them from the Autodesk Web site. APIs are used to communicate with the AutoCAD application, any open drawing files, and objects in a drawing. With some of the APIs, you can create your own custom commands that users can execute from the command line. The power behind some of these programming interfaces is that you don't need to be a programmer to take advantage of them.

Discovering What You Can Do by Programming AutoCAD

You might be thinking to yourself, "I'm not a programmer, so why do I want to know about programming interfaces?" The best reason to discover the programming interfaces is to simplify repetitive tasks in your workflow. If you can create very basic custom programs that save 15 minutes a day, the effort is worth your time - especially if you can share these programs with your coworkers.

Over time, your 15-minute savings can grow into much more as you become more efficient with the programming interface. Custom programs don't need to be complex to increase efficiency. They can be simple, like creating new commands that can be used to perform a Zoom Previous from the command line, or complicated, taking on issues such as CAD standards.

Managing CAD standards can be a nightmare, but the process can be improved by using programming interfaces. Tasks such as making sure dimensions are placed on the correct layer can be accomplished if you understand the programming interfaces and how AutoCAD works. You don't need to understand how the information is actually written to the file, but you do need to know how it is logically organized. By logically organized, we mean you should understand that objects such as layers aren't just floating around inside a drawing; instead, they are stored in a table that contains all the layers in a drawing.

The advantages of using APIs

The advantages of APIs differ based on whether you are already using third-party applications or add-ons for AutoCAD. Even if you are, you may still discover advantages to in-house programming. Here are some of the benefits for creating custom programs for AutoCAD:

* Accuracy: By creating a custom program that runs consistently every time, you can increase the accuracy of your drawings. If a process has a large number of steps in it, some steps might be overlooked. This can cause errors to creep into your design.

* Appearance: Programming can aid in making drawings look uniform by allowing you to set up drawing options that can't be defined in a drawing template or by allowing you to automate the updating of objects in a drawing.

* Efficiency: Repetitive tasks can be speeded up, enabling drafters to spend more time on the design process.

* Training efficiency: Training a new employee is always a challenge. If a complex or large set of processes must be followed, new employees take even longer to be productive. Wrapping custom programs around processes can help get them up and productive in a shorter period of time.

* The downstream effect: Being able to get things done faster and more efficiently during the drafting process is great, but don't forget about those people who use the data after the design has been completed. Custom programming can be used to extract information out of a drawing or set of drawings that can be useful downstream in manufacturing, sales and marketing, and many other areas.

The other side of the story

There are always two sides to every story. We've covered some of the benefits of using the programming interfaces in AutoCAD, but there has to be a downside, right? There is, and here are some of the disadvantages to programming in AutoCAD:

* Cost: Programming in AutoCAD costs money - how much depends on which programming interface you go with. These costs might be in the form of software, time, or consulting fees. In the case of a couple of the programming interfaces, no additional software packages need to be purchased, but, regardless, time is always a cost in these types of projects.

* Maintenance: AutoCAD changes from release to release. When you upgrade to a new version, you often have to spend time updating your custom programs. Some feature your custom program was using may get broken, or you may want to take advantage of a new feature that is introduced to improve a process even further.

* Learning curve: Even though a number of the programming interfaces are easy for non-programmers to pick up and understand, they still require you to put in some time if you want to become proficient. So before you promise your boss that you can deliver improved productivity, make sure you are comfortable with the programming language you chose first.

Getting to Know the Available Programming Interfaces

As AutoCAD has evolved over the years, so have the different programming interfaces that are available. When AutoCAD was first introduced to the world, no programming interfaces were built into the application. Only about three years after the product was released was the first programming interface added to the software. This programming interface was AutoLISP, which was based on the LISP programming language. The introduction of AutoLISP allowed users of AutoCAD to tailor the program for how they wanted to work to improve productivity.

After AutoLISP came the introduction of ADS (AutoCAD Development System), which introduced C-style coding as a programming option. ADS had a rather short life span because the C language was already being overshadowed by the next generation of the C programming language, C++. ADS, which was only around for about three years, evolved into ObjectARX, which is still the premier programming option in AutoCAD 2007. If you look at the install directory of AutoCAD, you can see that this is the tool of choice by Autodesk itself to extend the core functionality of AutoCAD.

In 1997, Autodesk...