C	MAIN LOGIC

	SUBROUTINE LOGIC

	INTEGER K,G,F1,R,S,L,M,EOL,EOS
	REAL	F,H,A,V,V1,V2,B,B0,V0,A0,H0,V9,D,D1,H8,H9,D2,T,C,I
	LOGICAL*1 ANSI(2),VT52(11)
	LOGICAL*1	W1,W2

	DATA ANSI/"33,"76/
	DATA VT52/"33,"133,"77,"62,"154,"33,"134,"33,"110,"33,"112/

	L=0
	M=0
	EOS="112
	EOL="113

	TYPE 799,ANSI,VT52		!VT100 TO VT52 COMPATIBILITY MODE
	TYPE 800
	TYPE 801
	TYPE 802
	TYPE 805

1	K=ITTINR()
	IF(K.LT.0)GO TO 1
2	IF(ITTOUR(K).NE.0)GO TO 2
	IF((K.EQ."116).OR.(K.EQ."156))GO TO 5
	CALL HOME
	CALL ERASE(EOS)
	CALL PAGE1
	K=ITTINR()			!SLUFF CR FROM PREVIOUS READ
3	CALL ISLEEP(0,0,1,0)
	K=ITTINR()
	IF (K.NE.13) GO TO 3
	TYPE 815
	CALL HOME
	CALL ERASE(EOS)
	CALL PAGE2
4	CALL ISLEEP(0,0,1,0)
	K=ITTINR()
	IF (K.NE.13) GO TO 4
5	CALL IPOKE("44,"50100.OR.IPEEK("44))
	TYPE 815
	CALL HOME
	CALL ERASE(EOS)
	CALL PANEL
	D=32000
	D1=30000
	I=0
	T=0
	C=281
	C1=281
	S=0
	G=0
	A0=7
	B0=0
	V0=0
	H0=2300
	V9=0
	F=1000
	F1=1
	H=2500
	A=8
	B=25
	V=125
	V1=0
	V2=0
10	A1=-32+V*SIN(A*6.28318531/180)
	H=H+V1+(.5*A1)
	V1=V1+A1
	V1=(V1+V2)/2
	V2=V1
	V=V-(.1*V)+(.5*B)-(.4*V1)-(10*G)
	IF(V.GT.55)GO TO 13
	S=1
13	IF(V.LT.80)GO TO 15
	S=0
15	IF(S.EQ.0)GO TO 17
	A=A-2
	H=H-50
17	F=F-ABS(B/4)
	IF(V.GT.64)GO TO 19
	IF(G.EQ.1)GO TO 19
	W1=58
	W2=10
	CALL CURFOR(W1,W2)
	TYPE 910
	CALL ISLEEP(0,0,0,30)
	CALL CURFOR(W1,W2)
	TYPE 911
	CALL ISLEEP(0,0,0,30)
	GO TO 20
19	CALL ISLEEP(0,0,1,0)
20	W1=58
	W2=6
	CALL CURFOR(W1,W2)
	Z=RAN(L,M)
	K=ITTINR()
	IF (K.LT.0) GO TO 32
	IF (K.EQ.65) GO TO 22
	IF (K.NE.26) GO TO 23
22	A=A+1
	GO TO 20
23	IF (K.EQ.66) GO TO 24
	IF (K.NE.11) GO TO 25
24	A=A-1
	GO TO 20
25	IF (K.EQ.68) GO TO 26
	IF (K.NE.8) GO TO 27
26	B=B-1
	GO TO 20
27	IF (K.EQ.67) GO TO 28
	IF (K.NE.24) GO TO 29
28	B=B+1
	GO TO 20
29	IF (K.NE.49) GO TO 30
	CALL LEFT(T)
	GO TO 20
30	IF (K.NE.50) GO TO 31
	CALL LEVEL(T)
	GO TO 20
31	IF (K.NE.51) GO TO 20
	CALL RIGHT(T)
	GO TO 20
32	IF(H.GT.0)GO TO 37
	IF(G.EQ.1)GO TO 33
	IF(V1.LT.-10)GO TO 300
	IF(D.GT.1500)GO TO 320
	IF(D.LT.-2500)GO TO 320
	IF(R.EQ.1)GO TO 37
	IF(V.GT.100)GO TO 200
33	H=0
	V1=0
	G=1
	IF(A.GT.8.0)GO TO 35
	A=8.0
35	A=A-1
	IF(V.LT.15)GO TO 315
	IF(B.EQ.0)GO TO 38
	B=B-1
	GO TO 38
37	G=0
	IF(R.EQ.0)GO TO 38
	R=0
	A=A-3
38	W1=3
	W2=12
	CALL CURFOR(W1,W2)
	TYPE 900,H
	W1=15
	W2=12
	CALL CURFOR(W1,W2)
	TYPE 900,V1
	IF(F.GE.0)GO TO 39
	F=0
	F1=0
39	B=B*F1
	W1=55
	W2=6
	CALL CURFOR(W1,W2)
	TYPE 900,F
	IF(B.LE.36.0)GO TO 40
	B=36
40	IF(B.GE.0)GO TO 42
	B=0
42	CALL POWER(B,B0)
	B0=B
	CALL SPEED(V,V0)
	V0=V
	CALL ATT(A,A0)
	A0=A
	CALL ALT(H,H0)
	IF(ABS(H-H0).LT.100.0)GO TO 45
	H0=H
45	CALL CLIMB(V1,V9)
	IF(ABS(V9-V1).LT.1.6)GO TO 47
	V9=V1
47	IF (T.EQ.0.) GO TO 50
	C=C+T
	IF (C.LT.361.) GO TO 48
	C=1
48	IF (C.GT.0.) GO TO 49
	C=360
49	W1=31
	W2=2
	CALL CURFOR(W1,W2)
	TYPE 900,C
50	IF(C.NE.C1)GO TO 52
	D=D-(1.5*V)
52	IF(G.EQ.1)GO TO 520
	IF(D.LT.1500)GO TO 500
	IF(D.LT.D1)GO TO 400
	GO TO 10

200	A=A+3
	R=1
	H=20
	GO TO 10


300	CALL HOME
	CALL ERASE(EOS)
	W1=30
	W2=9
	CALL CURFOR(W1,W2)
	CALL ISLEEP(0,0,1,0)
	TYPE 950
310	CALL ISLEEP(0,0,3,0)
315	CALL HOME
	CALL ERASE(EOS)
	CALL ISLEEP(0,0,1,0)
	GO TO 990

320	CALL HOME
	CALL ERASE(EOS)
	CALL ISLEEP(0,0,0,30)
	W1=10
	W2=9
	CALL CURFOR(W1,W2)
	TYPE 960
	GO TO 310

400	D1=D1-500
	W1=46
	W2=1
	CALL CURFOR(W1,W2)
	IF(D1.EQ.29500)GO TO 530
	IF(D1.EQ.29000)GO TO 535
	IF(D1.EQ.28000)GO TO 550
	IF(D1.EQ.21000)GO TO 540
	IF(D1.EQ.20000)GO TO 555
	IF(D1.EQ.18000)GO TO 545
	IF(D1.GT.17500)GO TO 10
	H9=.0875*D
	IF(H.LT.H9-50)GO TO 420
	IF(H.GT.H9+50)GO TO 440
	IF(I.GT.2)GO TO 560
	TYPE 700
	IF(T.NE.0)GO TO 10
	I=I+1
	GO TO 10

420	H8=H9-H
	TYPE 720,H8
	GO TO 10

440	H8=H-H9
	TYPE 740,H8
	GO TO 10

500	IF(D.GE.D1)GO TO 10
	D1=D1-500
	IF(D.GE.-2500)GO TO 510
	IF (H.GT.100)GO TO 515
	GO TO 300
510	D2=ABS(-3000-D1)
	W1=46
	W2=1
	CALL CURFOR(W1,W2)
	TYPE 790,D2
	GO TO 10

515	W1=46
	W2=1
	CALL CURFOR(W1,W2)
	TYPE 760
	GO TO 10

520	W1=46
	W2=1
	CALL CURFOR(W1,W2)
	TYPE 780
	GO TO 10

530	TYPE 710
	GO TO 10
535	TYPE 711
	GO TO 10
540	TYPE 712
	GO TO 10
545	TYPE 713
	GO TO 10
550	C3=120
	CALL COURSE(C3,C,C1,L,M)
	GO TO 10
555	C3=30
	CALL COURSE(C3,C,C1,L,M)
	GO TO 10
560	I=0
	C3=10
	CALL COURSE(C3,C,C1,L,M)
	GO TO 10

700	FORMAT('+You are on glidepath     '$)
710	FORMAT('+ You are in radar contact'$)
711	FORMAT('+ Descend to 1500 feet    '$)
712	FORMAT('+ Slow aircraft to 90 mph '$)
713	FORMAT('+ Begin 10 fps descent    '$)
720	FORMAT('+You are '$,F4.0,'feet low  '$)
740	FORMAT('+You are '$,F4.0,'feet high '$)
760	FORMAT('+Missed approach-go around'$)
780	FORMAT('+  NICE LANDING!!!        '$)
790	FORMAT('+',F5.0,' feet of runway left'$)
799	FORMAT (13A1)

800	FORMAT (' AIRCRAFT INSTRUMENT FLIGHT SIMULATION GAME')
801	FORMAT (' By Bill Greene, DIGITAL EQUIPMENT CORP.')
802	FORMAT (' Edited & Modified by Les Parent, DIGITAL')
805	FORMAT (' Do you need instructions?'$)

810	FORMAT (A3)
815	FORMAT('  ')
820	FORMAT(A1)


900	FORMAT ('+',F5.0$)
910	FORMAT('+*'$)
911	FORMAT('+ '$)
950	FORMAT ('+NOW YOU DID IT!!!'$)
960	FORMAT('+How did we get in this cornfield???'$)
980	FORMAT(' Do you want to fly again ? '$)
990	CALL HOME
	CALL ERASE(EOS)
	TYPE 980
995	K=ITTINR()
	CALL ISLEEP(0,0,3,0)
	IF(K.LT.0)GO TO 995
996	IF(ITTOUR(K).NE.0)GO TO 996
	IF((K.NE."116).AND.(K.NE."156))GO TO 5
	RETURN
	END
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