## Thursday, September 8, 2016

### TI-74 Programming: Factorial, List of Random Integers, 2 x 2 Matrix Determinant and Inverse, Simple Pendulum, Secret Codes

TI-74 Programming: Factorial, List of Random Integers, 2 x 2 Matrix Determinant and Inverse, Simple Pendulum, Secret Codes

Note:  The TI-74 has one programming space (lines 0 to 32768), which the entire space can be saved if the TI-74 connected to an appropriate peripheral (cassette or computer).  Cassettes?  The TI-74 is a 1980s basic computer after all.

TI-74 Program Factorial

The TI-74 does not have a factorial function its command set.  Here is one way to tackle it:

1300 ! Factorial
1310 INPUT “N=”; N
1320 IF N=0 THEN PRINT 0: PAUSE: STOP
1325 F=1
1330 IF I=1 TO N-1
1340 F=F*I
1350 NEXT I
1360 PRINT “N!=”; F: PAUSE
1370 END

TI-74 List of Random Integers

Integers will appear for 2 seconds followed by a “Next…” indicator.

1000 ! List of random integers
1005 RANDOMIZE
1010 INPUT “Length?”; K
1020 INPUT “High Number:”; N
1025 FOR I=1 TO K
1035 PRINT INT(N*RND+1): PAUSE 2
1040 PRINT “Next…”: PAUSE 0.5
1045 NEXT I
1050 PRINT “Done”: PAUSE: END

TI-74 2 x 2 Matrices: Determinant and Inverse

Matrix:  [[A, B],[C, D]]
Inverse:  [[F, G],[H, I]]
Determinant: E = A*D – B*C.  If E=0, the matrix is singular.

1100 ! 2 x 2 Matrices; det/inv
1105 INPUT “A=”; A, “B=”; B
1110 INPUT “C=”; C, “D=”; D
1115 E=A*D-B*C
1120 PRINT “det=”; E: PAUSE 2
1125 IF E=0 THEN STOP
1130 PRINT “inv=”: PAUSE 2
1135 F = D/E: G = -B/E: H=-C/E: I=A/E
1140 PRINT “F=”; F: PAUSE 2
1145 PRINT “G=”; G: PAUSE 2
1150 PRINT “H=”; H: PAUSE 2
1155 PRINT “I=”; I: PAUSE 2
1160 END

Example:
Matrix:  [[1, 5],[-2, 7]]
A=1,  B=5, C=-2, D=7

RUN 1100:
det = 17
inv =
F = .4117647059
G = -.2941176471
H = .1176470588
I = .0588235294

TI-74 Simple Pendulum:  Angular Velocity and Period

This routine calculates the angular velocity and period for a simple pendulum.  SI units are used, meaning that g = 9.80665 m/s^2.  Note the SQR command is square root.

1200 ! Simple Pendulum, SI unites
1205 G=9.80665
1210 INPUT “Length (m):”; L
1215 W=SQR(G/L): T=2*PI*SQR(L/G)
1220 PRINT “Angular Vel.:”; W; “m/s”:  PAUSE
1225 PRINT “Period:”; T; “s”: PAUSE
1230 END

Example:  L = 1.14 m
Results:  W = 2.932971967 m/s, T = 2.1422588902 s

TI-74 Secret 3 Digit Codes

I learn the PRINT USING and IMAGE commands for the first time here.  On the TI-74, # is a number field, the period (.) is the decimal point, ^ is the exponential character, and I can use spaces and text.  Yes, IMAGE is different on each of the basic calculators.

500  IMAGE ###   ###   (3 spaces in between the sets of hashtags)
505  PRINT “Here are the”: PAUSE 1
510  PRINT “secret codes!”: PAUSE 1
515  FOR I=1 TO 4
520 A=100*RND: B=100*RND
525 PRINT USING 500; A,B : PAUSE 1
530 NEXT I
540 END

Notes

1.     I am not able to use a variable while using a DIM command to size an array.  This is not allowed:

100 Z = 10
110 DIM A(Z)

2.     The commands and one-letter variables auto-capitalize when [ENTER] is pressed.  For example:

I type 100 print a, press [ENTER] and when look at the line again, the TI-74 displays:
100 PRINT A

3.     It is a good idea to put an END command after each routine.  END will tell the TI-74 stop, allowing multiple, separate routines in the TI-74 programming space.

4.    The amount of free memory is found by the formula:  FRE(0)-FRE(1).  The keyboard shortcut to FRE is [FN] [ ↓ ].

5.    If you want to clear the entire program space, type NEW ALL.

There will be more TI-74 programs in the near future.  Until next time,

Eddie

This blog is property of Edward Shore, 2016.

#### 1 comment:

1. This code is short and very easy to understand. As to perform the operations like factorial & matrix with online tools like calculate factorial is pretty easy but now with the use of your information, one can also create their own program to find out the factorial and matrix of various numbers. Great work!!!

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