**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.