I don't remember where I got this, but the source code itself says it was created as a modification of "CYBER 175" at the University of Illinois at Champagne by John Schugg. It runs fine under QBASIC or QuickBASIC, and I imagine it would run under BASICA/GWBASIC as well, considering the primitive programming conventions that are used (for one, line numbers).
ELIZA is supposed to simulate the act of speaking with a psychiatrist. I'm not sure how close this BASIC source is to the real deal, but I've heard that many test subjects found themselves convinced that ELIZA is a real person. Knowing that it's fake, I find it impossible to experience this for myself. It's quite easy to confound it and produce nonsensical replies. Type "shut up" to quit. Don't use commas, as it will give a "Redo from start" error due to the use of the INPUT command.
10 KEY OFF: SCREEN 0, 0, 0: COLOR 15, 1, 1: CLS
20 PRINT
30 DIM C1$(40)
40 GOSUB 1070
50 DIM C$(72), I$(72), K$(72), F$(72), S$(72), R$(72), P$(72), Z$(72)
60 DIM S(37), R(37), N(37)
70 N1 = 37
80 N2 = 14
90 N3 = 117
100 FOR X = 1 TO N1 + N2 + N3
110 READ Z$
120 NEXT X
130 FOR X = 1 TO N1
140 READ S(X), L
150 R(X) = S(X)
160 N(X) = S(X) + L - 1
170 NEXT X
180 PRINT "HI! I'M ELIZA. WHAT'S YOUR PROBLEM?"
190 REM
200 REM ----USER INPUT SECTION----
210 REM
220 INPUT I$
230 I$ = " " + I$ + " "
240 REM GET RID OF APOSTROPHES
250 FOR L = 1 TO LEN(I$)
260 IF MID$(I$, L, 1) <> "'" THEN 290
270 I$ = MID$(I$, 1, L - 1) + MID$(I$, L + 1, LEN(I$) - L)
280 GOTO 260
290 IF L + 4 >= LEN(I$) THEN 330
300 IF UCASE$(MID$(I$, L, 4)) <> "SHUT" THEN 330
310 PRINT "IF THAT'S HOW YOU FEEL--GOODBY..."
320 STOP
330 NEXT L
340 IF I$ <> P$ THEN 370
350 PRINT "PLEASE DON'T REPEAT YOURSELF!"
360 GOTO 190
370 REM
380 REM ----FIND KEYWORD IN I$----
390 REM
400 RESTORE
410 S = 0
420 FOR K = 1 TO N1
430 READ K$
440 IF S > 0 THEN 510
450 FOR L = 1 TO LEN(I$) - LEN(K$) + 1
460 IF MID$(I$, L, LEN(K$)) <> K$ THEN 500
470 S = K
480 T = L
490 F$ = K$
500 NEXT L
510 NEXT K
520 IF S <= 0 THEN 560
530 K = S
540 L = T
550 GOTO 590
560 K = 37 'WE DIDN'T FIND ANY KEYWORDS
570 GOTO 850
580 REM
590 REM TAKE RIGHT PART OF STRINGS AND CONJUGATE IT
600 REM USING THE LIST OF STRINGS TO BE SWAPPED
610 REM
620 RESTORE
630 FOR X = 1 TO N1
640 READ Z$
650 NEXT X
660 IF (LEN(I$) - LEN(F$) - L + 1) > 0 THEN 690
670 L = L - 1
680 GOTO 660
690 C$ = " " + MID$(I$, LEN(F$) + L, LEN(I$) - (LEN(F$) + L - 1))
700 FOR X = 1 TO N2 / 2
710 READ S$, R$
720 FOR L = 1 TO LEN(C$)
730 IF L + LEN(S$) > LEN(C$) THEN 770
740 IF MID$(C$, L, LEN(S$)) <> S$ THEN 770
750 C$ = MID$(C$, 1, L - 1) + R$ + MID$(C$, L + LEN(S$), LEN(C$) - (L + LEN(S$) - 1))
760 GOTO 810
770 IF L + LEN(R$) > LEN(C$) THEN 810
780 IF MID$(C$, L, LEN(R$)) <> R$ THEN 810
790 C$ = MID$(C$, 1, L - 1) + S$ + MID$(C$, L + LEN(R$), LEN(C$) - (L + LEN(R$) - 1))
800 L = L + LEN(S$)
810 NEXT L
820 NEXT X
830 IF MID$(C$, 2, 1) = " " THEN C$ = MID$(C$, 2, LEN(C$) - 1) 'ONLY 1SPACE
840 REM
850 REM NOW USING THE KEYWORD NUMBER (K) GET REPLY
860 REM
870 RESTORE
880 FOR X = 1 TO N1 + N2
890 READ Z$
900 NEXT X
910 FOR X = 1 TO R(K) 'READ RIGHT REPLY
920 READ F$
930 NEXT X
940 R(K) = R(K) + 1
950 IF R(K) > N(K) THEN R(K) = S(K)
960 IF MID$(F$, LEN(F$), 1) = "*" THEN 1000
970 PRINT F$
980 P$ = I$
990 GOTO 190
1000 PRINT MID$(F$, 1, LEN(F$) - 1); C$
1010 P$ = I$
1020 GOTO 190
1030 REM PRINT CENTER ROUTINE
1040 PRINT TAB(40 - LEN(C1$) / 2); C1$
1050 PRINT
1060 RETURN
1070 C1$ = "*** ELIZA ***"
1080 GOSUB 1030
1090 C1$ = "IN BASIC"
1100 GOSUB 1030
1110 C1$ = "MODIFIED FROM CYBER 175 AT UNIVERSITY OF ILLINOIS AT CHAMPAGNE"
1120 GOSUB 1030
1130 REM C1$ = "JOHN SCHUGG"
1140 REM GOSUB 650
1150 C1$ = "JANUARY 1985"
1160 GOSUB 1030
1170 C1$ = "HAVE ANY PROBLEMS ?"
1180 GOSUB 1030
1190 C1$ = "LET ELIZA HELP YOU !"
1200 GOSUB 1030
1210 PRINT
1220 C1$ = "TO STOP ELIZA TYPE 'SHUT UP'"
1230 GOSUB 1030
1240 C1$ = "(THIS VERSION WILL NOT RECORD YOUR CONVERSATIONS)"
1250 GOSUB 1030
1260 C1$ = "(PLEASE SEND SUGGESTIONS FOR IMPROVEMENTS TO JOHN SCHUGG)"
1270 GOSUB 1030
1280 PRINT "< PRESS RETURN TO CONTINUE...>"
1320 RETURN
1330 REM
1340 REM ---PROGRAM DATA FOLLOWS---
1350 REM
1360 REM KEYWORDS:
1370 REM
1380 DATA "CAN YOU","CAN I","YOU ARE","YOURE","I DONT","I FEEL"
1390 DATA "WHY DONT YOU","WHY CANT I","ARE YOU","I CANT","I AM","IM "
1400 DATA "YOU ","I WANT","WHAT","HOW","WHO","WHERE","WHEN","WHY"
1410 DATA "NAME","CAUSE","SORRY","DREAM","HELLO","HI ","MAYBE"
1420 DATA " NO","YOUR","ALWAYS","THINK","ALIKE","YES","FRIEND"
1430 DATA "COMPUTER","CAR","NOKEYFOUND"
1440 REM
1450 REM ---STRING DATA FOR CONJUGATIONS---
1460 REM
1470 DATA " ARE "," AM ","WERE ","WAS "," YOU "," I ","YOUR ","MY "
1480 DATA " IVE "," YOUVE "," IM "," YOURE "," YOU "," ME "
1490 REM
1500 REM ----REPLIES----
1510 REM
1520 DATA "DON'T YOU BELIEVE THAT I CAN*"
1530 DATA "PERHAPS YOU WOULD LIKE TO BE ABLE TO*"
1540 DATA "YOU WANT ME TO BE ABLE TO*"
1550 DATA "PERHAPS YOU DON'T WANT TO*"
1560 DATA "DO YOU WANT TO BE ABLE TO*"
1570 DATA "WHAT MAKES YOU THINK I AM*"
1580 DATA "DOES IT PLEASE YOU TO BELIEVE I AM*"
1590 DATA "PERHAPS YOU WOULD LIKE TO BE*"
1600 DATA "DO YOU SOMETIMES WISH YOU WERE*"
1610 DATA "DON'T YOU REALLY*"
1620 DATA "WHY DON'T YOU*"
1630 DATA "DO YOU WISH TO BE ABLE TO*"
1640 DATA "DOES THAT TROUBLE YOU?"
1650 DATA "TELL ME MORE ABOUT SUCH FEELINGS."
1660 DATA "DO YOU OFTEN FEEL*"
1670 DATA "DO YOU ENJOY FEELING*"
1680 DATA "DO YOU REALLY BELIEVE I DON'T*"
1690 DATA "PERHAPS IN GOOD TIME I WILL*"
1700 DATA "DO YOU WANT ME TO*"
1710 DATA "DO YOU THINK YOU SHOULD BE ABLE TO*"
1720 DATA "WHY CAN'T YOU*"
1730 DATA "WHY ARE YOU INTERESTED IN WHETHER OR NOT I AM*"
1740 DATA "WOULD YOU PREFER IF I WERE NOT*"
1750 DATA "PERHAPS IN YOUR FANTASIES I AM*"
1760 DATA "HOW DO YOU KNOW YOU CAN'T*"
1770 DATA "HAVE YOU TRIED?"
1780 DATA "PERHAPS YOU CAN NOW*"
1790 DATA "DID YOU COME TO ME BECAUSE YOU ARE*"
1800 DATA "HOW LONG HAVE YOU BEEN*"
1810 DATA "DO YOU BELIEVE IT IS NORMAL TO BE*"
1820 DATA "DO YOU ENJOY BEING*"
1830 DATA "WE WERE DISCUSSING YOU-- NOT ME."
1840 DATA "OH, I*"
1850 DATA "YOU'RE NOT REALLY TALKING ABOUT ME, ARE YOU?"
1860 DATA "WHAT WOULD IT MEAN TO YOU IF YOU GOT*"
1870 DATA "WHY DO YOU WANT*"
1880 DATA "SUPPOSE YOU SOON GOT*"
1890 DATA "WHAT IF YOU NEVER GOT*"
1900 DATA "I SOMETIMES ALSO WANT*"
1910 DATA "WHY DO YOU ASK?"
1920 DATA "DOES THAT QUESTION INTEREST YOU?"
1930 DATA "WHAT ANSWER WOULD PLEASE YOU THE MOST?"
1940 DATA "WHAT DO YOU THINK?"
1950 DATA "ARE SUCH QUESTIONS ON YOUR MIND OFTEN?"
1960 DATA "WHAT IS IT THAT YOU REALLY WANT TO KNOW?"
1970 DATA "HAVE YOU ASKED ANYONE ELSE?"
1980 DATA "HAVE YOU ASKED SUCH QUESTIONS BEFORE?"
1990 DATA "WHAT ELSE COMES TO MIND WHEN YOU ASK THAT?"
2000 DATA "NAMES DON'T INTEREST ME."
2010 DATA "I DON'T CARE ABOUT NAMES-- PLEASE GO ON."
2020 DATA "IS THAT THE REAL REASON?"
2030 DATA "DON'T ANY OTHER REASONS COME TO MIND?"
2040 DATA "DOES THAT REASON EXPLAIN ANY THING ELSE?"
2050 DATA "WHAT OTHER REASONS MIGHT THERE BE?"
2060 DATA "PLEASE DON'T APOLOGIZE."
2070 DATA "APOLOGIES ARE NOT NECESSARY."
2080 DATA "WHAT FEELINGS DO YOU HAVE WHEN YOU APOLOGIZE?"
2090 DATA "DON'T BE SO DEFENSIVE!"
2100 DATA "WHAT DOES THAT DREAM SUGGEST TO YOU?"
2110 DATA "DO YOU DREAM OFTEN?"
2120 DATA "WHAT PERSONS APPEAR IN YOUR DREAMS?"
2130 DATA "ARE YOU DISTURBED BY YOUR DREAMS?"
2140 DATA "HOW DO YOU DO--PLEASE STATE YOUR PROBLEM."
2150 DATA "YOU DON'T SEEM QUITE CERTAIN."
2160 DATA "WHY THE UNCERTAIN TONE?"
2170 DATA "CAN'T YOU BE MORE POSITIVE?"
2180 DATA "YOU AREN'T SURE?"
2190 DATA "DON'T YOU KNOW?"
2200 DATA "ARE YOU SAYING NO JUST TO BE NEGATIVE?"
2210 DATA "YOU ARE BEING A BIT NEGATIVE."
2220 DATA "WHY NOT?"
2230 DATA "ARE YOU SURE?"
2240 DATA "WHY NO?"
2250 DATA "WHY ARE YOU CONCERNED ABOUT MY*"
2260 DATA "WHAT ABOUT YOUR OWN*"
2270 DATA "CAN YOU THINK OF A SPECIFIC EXAMPLE?"
2280 DATA "WHEN?"
2290 DATA "WHAT ARE YOU THINKING OF?"
2300 DATA "REALLY, ALWAYS?"
2310 DATA "DO YOU REALLY THINK SO?"
2320 DATA "BUT YOU ARE NOT SURE YOU*"
2330 DATA "DO YOU DOUBT YOU*"
2340 DATA "IN WHAT WAY?"
2350 DATA "WHAT RESEMBLANCE DO YOU SEE?"
2360 DATA "WHAT DOES THE SIMILARITY SUGGEST TO YOU?"
2370 DATA "WHAT OTHER CONNECTIONS DO YOU SEE?"
2380 DATA "COULD THERE REALLY BE SOME CONNECTION?"
2390 DATA "HOW?"
2400 DATA "YOU SEEM QUITE POSITIVE."
2410 DATA "ARE YOU SURE?"
2420 DATA "I SEE."
2430 DATA "I UNDERSTAND."
2440 DATA "WHY DO YOU BRING UP THE TOPIC OF FRIENDS?"
2450 DATA "DO YOUR FRIENDS WORRY YOU?"
2460 DATA "DO YOUR FRIENDS PICK ON YOU?"
2470 DATA "ARE YOU SURE YOU HAVE ANY FRIENDS?"
2480 DATA "DO YOU IMPOSE ON YOUR FRIENDS?"
2490 DATA "PERHAPS YOUR LOVE FOR FRIENDS WORRIES YOU?"
2500 DATA "DO COMPUTERS WORRY YOU?"
2510 DATA "ARE YOU TALKING ABOUT ME IN PARTICULAR?"
2520 DATA "ARE YOU FRIGHTENED BY MACHINES?"
2530 DATA "WHY DO YOU MENTION COMPUTERS?"
2540 DATA "WHAT DO YOU THINK MACHINES HAVE TO DO WITH YOUR PROBLEM?"
2550 DATA "DON'T YOU THINK COMPUTERS CAN HELP PEOPLE?"
2560 DATA "WHAT IS IT ABOUT MACHINES THAT WORRIES YOU?"
2570 DATA "OH, DO YOU LIKE CARS?"
2580 DATA "MY FAVORITE CAR IS A LAMBORGINI COUNTACH. WHAT IS YOUR FAVORITE CAR?"
2590 DATA "MY FAVORITE CAR COMPANY IS FERRARI. WHAT IS YOURS?"
2600 DATA "DO YOU LIKE PORSCHES?"
2610 DATA "DO YOU LIKE PORSCHE TURBO CARRERAS?"
2620 DATA "SAY, DO YOU HAVE ANY PSYCHOLOGICAL PROBLEMS?"
2630 DATA "WHAT DOES THAT SUGGEST TO YOU?"
2640 DATA "I SEE."
2650 DATA "I'M NOT SURE I UNDERSTAND YOU FULLY."
2660 DATA "COME COME ELUCIDATE YOUR THOUGHTS."
2670 DATA "CAN YOU ELABORATE ON THAT?"
2680 DATA "THAT IS QUITE INTERESTING."
2690 REM
2700 REM ---DATA FOR FINDING RIGHT REPLIES---
2710 REM
2720 DATA 1,3,4,2,6,4,6,4,10,4,14,3,17,3,20,2,22,3,25,3
2730 DATA 28,4,28,4,32,3,35,5,40,9,40,9,40,9,40,9,40,9,40,9
2740 DATA 49,2,51,4,55,4,59,4,63,1,63,1,64,5,69,5,74,2,76,4
2750 DATA 80,3,83,7,90,3,93,6,99,7,106,5,111,6
2760 REM
2770 REM
2780 REM LAST MOD. JULY 1979
2790 REM
2800 REM ' ELIZA '
2810 END
HI! I'M ELIZA. WHAT'S YOUR PROBLEM?
? I'M AFRAID OF THE DARK
DID YOU COME TO ME BECAUSE YOU ARE AFRAID OF THE DARK
? YES
ARE YOU SURE?
? WHY ELSE WOULD I BE HERE
WHY DO YOU ASK?
? BECAUSE YOU ASKED IF I WAS SURE
WE WERE DISCUSSING YOU-- NOT ME.
? FINE... WHAT SHOULD I DO?
WHY DO YOU ASK?
? BECAUSE YOU ARE MY PSYCHIATRIST
WHAT MAKES YOU THINK I AM YOUR PSYCHIATRIST
? I FUCKING PAID YOU $150 AN HOUR TO BE ONE
OH, I $150 AN HOUR TO BE ONE
? WHAT?
DOES THAT QUESTION INTEREST YOU?
? YES
I SEE.
? I WANT A FAST CAR
WHAT WOULD IT MEAN TO YOU IF YOU GOT A FAST CAR
? FAST WOMEN
SAY, DO YOU HAVE ANY PSYCHOLOGICAL PROBLEMS?