# CoVID-19 SEIR model implemented in TI-66 AOS
# before running program, store S0 (01), E0 (02), I0 (03), R0 (04), alpha (05), beta (06), gamma (07), rho (08), dt (09), and tmax (10)
# after running program, recall Sn (01), En (02), In (03), and Rn (04)
000 LBL 
001 A
# get nsteps from tmax over dt
002 RCL 
003 10
004 /
005 RCL 
006 09
007 =
008 STO 
009 00 # nsteps in 00
# calculate dS
010 RCL 
011 08
012 *
013 RCL
014 06
015 *
016 RCL 
017 01
018 *
019 RCL
020 03
021 *
022 RCL 
023 09
024 =
025 +/-
026 STO
027 11 # dS in 11
# calculate dE
028 (
029 RCL
030 08
031 *
032 RCL
033 06
034 *
035 RCL 
036 01
037 *
038 RCL
039 03
040 -
041 RCL
042 05
043 *
044 RCL
045 02
046 )
047 *
048 RCL
049 09
050 =
051 STO
052 12 # dE in 12
# calculate dI
053 (
054 RCL 
055 05
056 *
057 RCL 
058 02
059 -
060 RCL
061 07
062 *
063 RCL
064 03
065 )
066 *
067 RCL 
068 09
069 =
070 STO
071 13 # dI in 13
# calculate dR
072 RCL
073 07
074 *
075 RCL
076 03
077 *
078 RCL
079 09
080 =
081 STO
082 14 # dR in 14
# calculate new S, E, I, and R
083 RCL 
084 11
085 SUM
086 01 # add dS to Sn-1
087 RCL 
088 12
089 SUM
090 02 # add dE to En-1
091 RCL
092 13
093 SUM
094 03 # add dI to In-1
095 RCL 
096 14
097 SUM
098 04 # add dR to Rn-1
# do again for nsteps (00)
099 DSZ
100 00
101 00
102 10
103 RTN