1. The PLATO Computer System and Cheating at Multiplayer Online Games
Bruce Maggs

2. Your professor is a notorious cheater
A small confession…
Your professor is a notorious cheater

3. PLATO Computer System
PLATO IV Developed by the University of Illinois and the Control Data Corporation
1961 timesharing PLATO II begins
1964 invention of plasma panel
1968 PLATO IV begins
Spun off as “NovaNET” late 1980’s
Revived at

4. Innovations first LARGE on-line community
invention of the plasma panel
multimedia
“personal notes” –
“group notes” – newsgroups
“consulting mode” – desktop sharing
widely used “term talk” (like Unix talk)
Shared memory enabled multiplayer games
IBM correctly attributes Lotus Notes to PLATO

5. Foreign Languages Building, University of Illinois

7. Hardware Control Data mainframes designed by Seymour Cray
Cyber 70, 176, CDC 6600, 7600
Magnetic core memory
60-bit words, 6-bit characters
One’s-complement arithmetic
Up to 1000 simultaneous users
(NovaNET originally ran on Alpha processor)

8. Login Screen

9. NovaNET

10. CDC 6600
$6,891,300
131K words
four arms:
CPU
memory
peripheral processors
“small” disks (previously 1m)

11. Operator’s Console

12. PLATO IV terminal 512 x 512 pixel plasma (neon gas) panel
screen is a write-only memory
Bitzer, Slottow, Willson, won emmy for invention of plasma panel (2002)
1200-baud connection
built-in touch panel
built-in rearview slide projector
external audio device (large read-write floppy disks)

13. PLATO IV Terminal
From

14. Terminal Commands Load customizable character set
Display text at coordinate
Draw a line between a and b
Implemented in hardware

15. File System Global namespace (no directories!)
8-character file names (no extensions)
File types
Tutor programs
Datasets
Namesets
Notesfiles
Groups

16. TUTOR Programming Language
All “lessons” written in TUTOR
Interpreted
Program size limited by memory constraints
Apparently not designed by computer scientists
(FORTRAN and assembly code available to system programmers)

17. Early Tutor 150 variables Could assign names to these variables
n1, …, n150 (integers) or
v1, …, v150 (floating point)
Could assign names to these variables
“jump” between “units” (like C functions)
“do loop” (like C for loop)
“conditional branch” (a.k.a. goto)

18. Later TUTOR Improvements
“do” (call a function) - stack depth 10
return values
recursion
local variables
if, else
while, repeat until

19. Users and Groups

20. On-line Community

21. Privileges Student Mode Author mode Super users Can only run programs
Can run programs, edit files
Super users
Members of groups s, p, o, e

22. Author Mode

23. Foreground vs. Background Modes
Foreground mode limited to 10 TIPS (Thousand Instructions Per Second)
Background mode: no guarantees, but also no limits on CPU share; don’t try during the day
Disk access rate above 10 DAPM (Disk Accesses Per Minute) frowned upon

24. Concurrency Primitives
No mutexes, semaphores, etc.
Undocumented feature: time slice will not be interrupted in straight-line (i.e., no backwards branches) calc code
loop
. if mutex = 0
mutex  1
outloop
. endif
endloop

25. The branch q purge
branch q branched to end of straight-line code (or something like that)
System was taken down
All TUTOR files were scanned
branch q replaced by branch to explicit label

27. Pressing the STOP key aborts output stream to the terminal.
I pressed NEXT, then quickly pressed STOP several times, which allowed me to trace Rick Blomme’s record, and beat it!

28. Common Memory Upto 8000 words shared by all users of a lesson
Persistent, backed by disk
Could load up to 1500 words into core storage (memory) at any time, nc1, …, nc1500 or vc1, …, vc1500
Provided communication between multiple users of a program, e.g., between players in a game

29. Multiplayer Games Dungeons and Dragons Space Combat orthanc, avatar
empire, spasim
Combat
dogfight, panther, airfight

30. Empire

31. Empire Basics I am  shrike , a proud Klingon / Kazari
Becoming a member of the Federation, a Vulcan/Orion, or a Romulan is equivalent to turning in your private key
The goal is to conquer the universe
Ship fires phasers, photon torpedos
Firing at correct angle inflicts more damage. To fire phasers at angle 233, type “f 233 NEXT”
Ship makes a hyperjump when you replot the screen, based on time since last replot

32. Empire

33. The Clone Brothers
I built a device that you plugged a keyboard into, and then it plugged into two separate PLATO IV terminals
Small circuit waited for both terminals to acknowledge keystroke before telling keyboard
Why? Fly two ships to same location in empire, then have double the firepower!
Nicknamed the “Clone Brothers” device migrated to different clusters of PLATO terminals around campus at U of I

34. PLATO V Terminal Plasma panel and CRT versions Same 512 x 512 display
8080 processor implemented all graphics

35. PLATO V Terminal
From

36. Empire Bot
8080 had access to stream of commands sent to terminal from mainframe
I wrote assembly code to determine angles to enemies on the screen (using an arctan look-up table)
Program displayed exact angle above each enemy, with keyboard shortcuts to fire phasers or torpedos at that angle
Also displayed a growing ellipse around ship to indicate distance of hyperjump
Possibly the first shooter-game bot ? (“shoot’ em up” or “arcade shooter” genre)

37. Avatar

38. Avatar Basics
Players join different guilds, e.g., fighter, magician, cleric, and gain different capabilities
Players form groups and enter the dungeon together to fight monsters and gather treasures
At one time possibly most popular multi-player on-line game in the world
Co-authored with David Sides and Andrew Shapira, with help from many others
My current character is dead on level one

39. Avatar

40. Duplicating Magical Items
Strategy: give all of your magical items and gold to a friend, the crash the game before the changes to your character are recorded to disk!
Negative: “unfair” and throws the game economy out of whack
Positive: we quickly find out about serious bugs

41. Best Consulting Gig Ever
I am hired by Jagex, maker of Runescape to document that third-party bots really work
My character is exempted from being banned for using bots
My kids complain that I am a cheater

42. Runescape

43. How do the bots work? Runescape is a Java applet
Bot maker provides Java applet container
Bot does not scrape the screen, but instead examines the bytecode
Bot determines position on screen of character, objects, etc.

44. Anti-Bot Measures Code is rearranged in different instances of applet
Ultimately, all data stored in one master array, permuted in random order, killing bots!
Many players quit when bots were defeated

45. Wallhacks
How do these hacks work? Game client has complete model of the world containing shapes and textures of objects, but asks the 3D graphics card to render it only from a particular first-person point of view. Changing textures, e.g., can make them transparent.