TI-80 |

TI-80 (left), TI-84 Plus CE (right) |

Look how thin the TI-80 is |

**Retro Review: Texas Instruments TI-80**

First, thank you Nano for the TI-80 (along with giving me a
pair of slide rules and an astronomy poster)!
Much appreciated!

**Essentials**

Company: Texas Instruments

Years: 1995

Type: Graphing, Programming

Memory: 7,034 bytes

Operating System: Algebraic

Memory Registers:
27 (A-Z, θ)

Screen: Monochrome

Batteries: 2 CR2032 batteries

Graphing
Modes: Function (4), Parametric (3). Table included.

Regressions: 6: Linear (ax + b), Quadratic, Linear (a +
bx), Logarithmic, Exponential, Power

Lists: Up to 99
entries per lists, 6 lists available (L1 through L6)

Matrices: none

Complex
Numbers: none

**Keyboard**

The keyboard is
what one would expect on a Texas Instruments graphing calculator: nice and
responsive.

**Screen**

The screen is
small. Not kidding. The screen is only 48 x 64 pixels big,
accompanying 8 lines of 16 characters. That
means that the font is small. What is wild
is that the pi symbol (π) does not conform to the rest of the font, and is
twice as long as the rest of the characters.

The screen is still
bigger than the mini-graphing calculators such as the Casio fx-6300g or the
Hewlett Packard HP-9g.

**Is the TI-80 a simplified TI-81?**

For the most part,
no. Sure, the TI-80 does not have
matrices and hyperbolic functions (sinh, cosh, etc) like the TI-81. However, the TI-80 has fractions (see the
next section), integer division and remainder function, random integer, a complementary
table mode, and lists. The number of
stat plots increased to 3, which they don’t have to depend on the statistics
mode.

As far as
programming memory, the TI-80 beats the TI-81: 7,034 bytes to 2,400 bytes. Also, you can go beyond 37 programs for the
TI-80, as the names are not restricted to one character.

**Fractions**

The TI-80 has a
dedicated fraction menu, which allow users to convert between improper and
proper form, as well as conversion between fraction and decimal approximation. The Manual Simplification mode allows
fractions to not be automatically simplified on calculation.

To enter fractions,
the format is: A _ B

**/**C
Note that the slash
is bold. Merely pressing the division key
will not register the fraction.

To separate the
whole part from the fraction, press [ 2nd ] [ + ] (UNIT_).

To separate the
numerator from the denominator, press [ 2nd ] [ ÷ ] (b/c).

Example: Enter 2 3/4

Keystrokes: 2 [ 2nd ] [ + ] 3 [ 2nd ] [ ÷ ] 4

According to
Datamath (http://www.datamath.org/Graphing/TI-80.htm
), the TI-80 would get replaced with the TI-73 in 1998. This may mean that the TI-80 became the base
for the TI-73 series (TI-73, TI-73 explorer).

**Lists**

The TI-80 allows
for 6 lists, each with a 99 element capacity.
Arithmetic can be operated on two same-sized lists, on an
element-by-element functions. Lists
functions include sorting, dimension, minimum, maximum, sum of the elements,
product of the elements, and sequence generation.

**Programming**

Programming is
fairly basic for the TI-81. Commands:

If-Then-Else-End
Structure (IF, THEN, ELSE, END)

Quick if structure

For-End structure
(no IS>, DS< this time) (FOR, END)

Labels: one character and local labels (LBL, GOTO)

Subroutines (PRGM_,
RETURN)

Drawing commands
include points, shading (three types, general, Y<, Y>)

Since the only
built-in calculus function of the TI-80 is numerical derivation (NDERIV), two
programs for Newton’s Method and Simpson’s Rule are presented below.

**TI-80 Program: SOLVEY1 (Newton’s Method)**

80 bytes

The equation is
stored in Y1. The program solves for X
in Y1(X) = 0

INPUT “GUESS:”, X

LBL 0

X-Y1/NDERIV(Y1,X,X)→N

IF ABS (X-N)>1E-10

THEN

N→X

GOTO 0

END

N→X

DISP “X = “, X

Example: X^2-3X+1, guess X = 3

Result: X =
2.618033989

**TI-80 Program: SIMPY1 (Integral, Simpson’s Rule)**

140 bytes

The equation is
stored in Y1. The program calculates ∫(Y1,X,A,B)

RADIAN

INPUT “A:”,A

INPUT “B:”,B

INPUT “N (EVEN):”,N

(B-A)/N→H

0→T

FOR(I,1,N-1)

A+IH→X

T+2*Y1→T

IF FPART(I/2)≠0

2*Y1+T→T

END

(T+Y1(A)+Y1(B))H/3→T

DISP “INTEGRAL:”,T

Example: X^2-3X+1, with A = 0 to B = 5 and N = 10

Result: X = 9.166666667

**Final Verdict**

The TI-80 is a nice introductory calculator, and thanks to
programming a lot can be done with it. I
wish the screen was bigger and degree/degrees-minutes-seconds conversions were
available, but other than that, it was a great calculator which provides a lot
of features (maybe not as intimidating as more advanced calculators).

It is a nice calculator to add to the collection, and I thank you Nano
immensely.

Eddie

This blog is property of Edward Shore, 2017.