By Justin Karneeb

 Many people have different views  It is not a High-Level language  It has low functionality (innate abilities)  It has minimal debugging tools  It simplifies a complex task for another program So what is the answer??

 A scripting language, script language or extension language, is a programming language that controls a software application.  But that is a very vague response…… but because of the debate, I guess it has to be.

 There is one thing that everyone agrees on  It is almost always used to solve a task for another program Scripting Languages are languages where there core use is to extend the use of another language or piece of software.

 There are two parts to a scripting language  The Language itself  Defines syntax just like a High-Level language  The Engine/Interpreter  A scripting language normally runs in a virtual machine similar to Java.

 Most programming languages compile into machine code/assembly  Scripting languages mostly compile into what is know as a bytecode stream.  It contains simpler instructions than the language itself, but not as simple as assembly.

 Also known as a Virtual Machine or VM.  The VM takes the bytecode stream and runs it.  This is generally slower than it running innately, however it also has many positives as well.  Since they are running independently from the main program, the entire program will not crash if there is a problem.

 You can use a scripting language to do almost any task, however it is suited to some more than others  Anything which needs to be multiplatform  Anytime in which non programmers need to have direct access to the behavior of a program  When gluing different pieces of software together or to have them communicate effectively.

 Webpages are perfect places to utilize scripting languages.  Since they need to be multiplatform, their VM based compiling/running is extremely handy.  HTML, PHP, XML, SWF, these are all scripting language extensions.

 This allows developers to work on parts of the program that do not necessarily require the completed program.  This is also applicable in games, developers can begin work on mapping and scripting npcs while the game itself is still under development.

 Many NPCs in video games are completely scripted  The path the walk, what they say and even what they do is coded in a scripting language which communicates with the engine.  The infamous Half-Life Marines were scripted to move in a specific way

Some games release scripting languages complete with API’s for the gamer community to use to “mod” their game.  Unreal tournament allows users to make custom bots  The original Half-Life had many scripting capabilities through programs like AMX

 As with everything, scripting languages have their upsides an downsides  Scripting languages seem to have more ups than downs, especially as technology gets better and faster

 Allows developers to work independently of the programmers  Easy to understand and use compared to languages like c++ and java  Does not crash program, less error prone  Scripts can be put on hold  Is multiplatform  Has a data-driven design  Allows a modding community to extend a game

 Most do not have debugging tools  Runs extremely slowly when compared to fully compiled code  Normally has less functionality, less innate abilities  Using scripts too much (in games) can lead to boring gameplay  Overdependence on scripting can lead to horrible problems late in development (using too much processing power)

 We have dealt with what scripting languages are, when to use them and how they work, now its time to show some real examples of scripting languages in action.  Far Cry Instincts  Half-Life

 A console based FPS which takes place on several islands.  The game is made to be played by sneaking around, which presented a serious problem  NPCs on the island needed to look as if they had a purpose.  How would you code hundreds of different NPCs to independently do normal activities?  Scripting Languages : )

 Originally, Ubisoft tried to code their behaviors directly into the NPCs behavior  They decided to take a new approach where developers could place “Anchors” on things in game.  The anchor would tell the NPC what to do next

 At first they were simple, but they soon expanded their use.  An anchor can play animations, trigger events, issue commands and just about anything else an NPC would want to do

 The developers were not versed in programming, so they decided to go with XML  It fit in well with their engine  Was overall easy to learn  XML is a text based scripting language that is powerful enough to get the job done

 The developers needed to get used to the XML code  Some picked it up fast, but not everyone  Because the coding is generally easy, the programmers were able to make a GUI interface which could be used to write the code for the developers.

 Because the developers were unfamiliar with the subtitles of programming, they ran into some problems  Ignore All command lead to many problems  Vehicles could not use anchors  Physics issues

 I have personal experience with scripting for Half-Life, specifically counterstrike and some other mods.  Half-Life itself has been modded more times than I prefer to count.  My experience is with AMX, it makes minor changes to the games.

 AMX is a scripting language made specifically for Half-Life modifications.  It starts as a text file which gets compiled into a.AMX file  AMX links with the Half-Life engine and while in game runs “plugins” that are written by the modders.  When you combine AMX’s plugins with the already modded HL engine, there are millions of different gameplay options available.

 Ninja Rope  Allowed you to swing from any surface via a “rope”  Slap  Allowed admins/users to “slap” (do 1 damage and knock the slapie around a bit) players  Predator  Made one user invisible, gave them extra health and speed.  Defend Your Castle/Force Grab

 The plugin asked the engine who the user was currently looking at, and returned to it its x,y, and z positions in the plane  When activated, as the user moved his/her cursor, the x,y and z coordinates of the player being grab were updated to that new location (the distance between them remained constant)

 While we were able to achieve a very high toss into the air, which would kill players in impact, if you forcibly drove a player into the ground and he died while being grabbed, the plugin would crash.  Half-Life was unaffected however AMX would stop working until the server was restarted.  We were never able to solve this problem, there seemed to be no exception handling in AMX.

 I learned a lot about scripting languages back then even though I had no idea what I was doing.  It was extremely powerful  It was hard to debug  It was easy to learn  I had never programmed before  When it crashed, it did not ruin the game  It fit our definition perfectly.