The TI-59 was a truly amazing calculator when it was introduced in 1977. A mind-boggling 960 program steps, 100 memories, a magnetic card reader, a rich variety of built-in functions, solid-state program ROM modules, and on top of that, an optional external printer/docking station made this beast a true geek dream machine. I remember going to sleep with a TI-59 brochure in my hands back when I was 15 or so... (well, I was also interested in girls, so I wasn't a hopeless case!)

Of course it was an unattainable dream; a price of several hundred dollars just for the calculator itself was too much even for most American kids of my age. However, a few years later, I did in fact come in close contact with this machine, when I was writing flight simulation software for the Hungarian air traffic management authority.

As it turns out, I still have a few of those old magnetic cards in my possession. Having recently obtained a TI-59 that works really well, I was amazed to find out that the cards are actually readable after almost 20 years. It took a few tries but I was able to load, and print, several of my old programs, including the one calculating take-off distances for passenger jets under various load, runway, and engine conditions. It was amazing to see those old programs come to life, and follow the take-off of a TU-154 again as rows of numbers representing distance, speed, and altitude began to appear in printout.

Except for a richer instruction set and some keycode merging (not nearly as extensive though as the merging on HP calculators) the TI-59 has a very similar programming model to that of the SR-52. Of course those extra features made a world of a difference; for instance, the TI-59 was the first pocket calculator that knew about letters, not just numbers. Although its display used traditional 7-segment digits, the TI-59 was capable of printing arbitrary text on the PC-100 printer.

Apparently, the TI-59's card reader suffers from the same disease as Hewlett-Packard's card readers in their early calculators: the rubber of its pinch wheel disintegrates over time, turning into a yucky, gummy deposit. Because there's more friction along the card path than in HP calculators, it appears this calculator is more sensitive to the exact geometry of the wheel. So although I have made several attempts, I have yet to claim that I have repaired a TI-59's card reader to a degree that I'd call satisfactory. Fortunately, several of my TI-59s still have their wheels intact.

The TI-59 had two smaller cousins. The TI-58 had about half the memory and no card reader, which meant that programs were lost when the calculator was powered down. The TI-58C was a TI-58 with continuous memory.

All three calculators in this family have undocumented features. Most notable among these is the infamous HIR instruction, which allows the programmer to access a variety of hidden ("hierarchy") registers.

Solid-state modules really added to the power of these calculators. With these modules, it is actually possible to create a complex implementation of the Gamma function for the TI-59. The version shown here uses 309 program steps, so it fits on the two sides of a single magnetic card.

The program calculates the complex Gamma function for any complex argument, entered using the x-t key. For instance, to calculate the Gamma function of 1+3i, you'd type 1 x-t 3 A. After a somewhat lengthy computation, the calculator will display the real part of the result (0.019292759); the imaginary part (.0338960105) can be retrieved using x-t again. To calculate the Gamma function of a real number such as 5, type 5 x-t 0 A.

Note that this program requires the presence of the Master Library 1 module in the calculator's Solid State Library slot. If the module is not present, or if another module is inserted, the program will not function correctly.

000 76	LBL
001 11	A
002 42	STO
003 04	04
004 32	x-t
005 42	STO
006 03	03
007 01	1
008 42	STO
009 01	01
010 00	0
011 42	STO
012 02	02
013 29	CP
014 76	LBL
015 32	x-t
016 43	RCL
017 03	03
018 77	x>=t
019 61	GTO
020 36	PGM
021 04	04
022 13	C
023 01	1
024 44	SUM
025 03	03
026 61	GTO
027 32	x-t
028 76	LBL
029 61	GTO
030 43	RCL
031 01	01
032 42	STO
033 05	05
034 43	RCL
035 02	02
036 42	STO
037 06	06
038 02	2
039 65	×
040 89	π
041 95	=
042 34	√
043 42	STO
044 01	01
045 00	0
046 42	STO
047 02	02
048 36	PGM
049 04	04
050 13	C
051 93	.
052 08	8
053 06	6
054 07	7
055 06	6
056 00	0
057 04	4
058 03	3
059 04	4
060 02	2
061 04	4
062 85	+
063 08	8
064 03	3
065 95	=
066 44	SUM
067 01	01
068 36	PGM
069 04	04
070 13	C
071 93	.
072 09	9
073 02	2
074 06	6
075 04	4
076 09	9
077 04	4
078 07	7
079 09	9
080 85	+
081 01	1
082 01	1
083 06	6
084 08	8
085 95	=
086 44	SUM
087 01	01
088 36	PGM
089 04	04
090 13	C
091 93	.
092 02	2
093 04	4
094 05	5
095 02	2
096 09	9
097 07	7
098 00	0
099 05	5
100 85	+
101 08	8
102 06	6
103 08	8
104 07	7
105 95	=
106 44	SUM
107 01	01
108 36	PGM
109 04	04
110 13	C
111 93	.
112 02	2
113 09	9
114 05	5
115 01	1
116 04	4
117 07	7
118 07	7
119 85	+
120 03	3
121 06	6
122 03	3
123 00	0
124 08	8
125 95	=
126 44	SUM
127 01	01
128 36	PGM
129 04	04
130 13	C
131 93	.
132 06	6
133 02	2
134 07	7
135 08	8
136 09	9
137 05	5
138 02	2
139 85	+
140 08	8
141 00	0
142 09	9
143 01	1
144 06	6
145 85	+
146 53	(
147 93	.
148 06	6
149 03	3
150 03	3
151 01	1
152 05	5
153 03	3
154 85	+
155 07	7
156 05	5
157 01	1
158 02	2
159 02	2
160 54	)
161 48	EXC
162 01	01
163 95	=
164 42	STO
165 07	07
166 00	0
167 48	EXC
168 02	02
169 42	STO
170 08	08
171 36	PGM
172 04	04
173 18	C'
174 43	RCL
175 07	07
176 44	SUM
177 01	01
178 43	RCL
179 08	08
180 44	SUM
181 02	02
182 01	1
183 44	SUM
184 03	03
185 94	+/-
186 49	PRD
187 04	04
188 36	PGM
189 04	04
190 18	C'
191 01	1
192 44	SUM
193 03	03
194 94	+/-
195 49	PRD
196 04	04
197 36	PGM
198 04	04
199 18	C'
200 01	1
201 44	SUM
202 03	03
203 94	+/-
204 49	PRD
205 04	04
206 36	PGM
207 04	04
208 18	C'
209 01	1
210 44	SUM
211 03	03
212 94	+/-
213 49	PRD
214 04	04
215 36	PGM
216 04	04
217 18	C'
218 01	1
219 44	SUM
220 03	03
221 94	+/-
222 49	PRD
223 04	04
224 36	PGM
225 04	04
226 18	C'
227 01	1
228 44	SUM
229 03	03
230 94	+/-
231 49	PRD
232 04	04
233 36	PGM
234 04	04
235 18	C'
236 36	PGM
237 05	05
238 16	A'
239 43	RCL
240 03	03
241 75	-
242 93	.
243 05	5
244 95	=
245 48	EXC
246 01	01
247 42	STO
248 07	07
249 43	RCL
250 04	04
251 94	+/-
252 42	STO
253 04	04
254 48	EXC
255 02	02
256 42	STO
257 08	08
258 36	PGM
259 05	05
260 16	A'
261 05	5
262 93	.
263 05	5
264 22	INV
265 44	SUM
266 03	03
267 36	PGM
268 04	04
269 13	C
270 43	RCL
271 08	08
272 75	-
273 43	RCL
274 04	04
275 95	=
276 44	SUM
277 02	02
278 43	RCL
279 07	07
280 75	-
281 43	RCL
282 03	03
283 75	-
284 05	5
285 95	=
286 44	SUM
287 01	01
288 36	PGM
289 05	05
290 17	B'
291 43	RCL
292 05	05
293 42	STO
294 03	03
295 43	RCL
296 06	06
297 42	STO
298 04	04
299 36	PGM
300 04	04
301 18	C'
302 43	RCL
303 02	02
304 32	x-t
305 43	RCL
306 01	01
307 92	RTN

Do you want to test drive a TI-59 yourself without spending an arm and a leg to buy one in questionable condition on eBay? I recently came across a wonderful TI-59 emulator on the Web: http://www.n3times.com/vertigo/ is the address. The emulator isn't 100% complete yet, but it's pretty darn close and it's pretty darn good, too!