The Compucorp 324G Scientist is not only the oldest calculator in my collection, it is also by far the most beautiful (despite the missing transparent plastic piece that used to cover the display.) I fell in love with this machine the moment I unpacked it. Even after more than 25 years, the calculator looks and feels like a professionally designed, true scientific instrument.

These "Micro-Computers" from Computer Design Corporation were far ahead of their time. Manufactured in the early seventies, these large, yet portable calculators are stunningly elegant, with a crisp, bright Apollo-era plasma fluorescent display and a 10+ digit calculation accuracy that puts many later models (in particular, such notoriously inaccurate ones as the Novus 4525 or the Sinclair Cambridge Programmable) to shame.

The Compucorp 324G provides ten registers of storage and a program space of 160 program steps, divided into two program areas of equal size. Programs are mere keystroke sequences; no control transfer or conditional execution instructions are provided. However, program execution loops around at the end of program memory, and stops on an error, which makes it possible to implement simple iterations in a fashion similar to that used on the TI-55.

For instance, here is a factorial program for the 324G. This program halts with an error on the display; to obtain the result, hit RESETand retrieve the contents of register 0.

01    STn
02    1
03    1/x
04    RCLn
05    1
06    ×
07    STn
08    0
09    (
10    RCLn
11    1
12    -
13    1
14    )

These Compucorp calculators have many oddities. For instance, pressing a dual-function key such as the Ln/LOG key calculates both functions at the same time; you press the 2ND FUNC key afterwards to swap between the results of the top vs. the bottom function. It so happens that the 2ND FUNCkey can also be used for temporary storage under certain circumstances, letting you save a program step here and there.

Display accuracy is controlled by the SET D.P.key. During program load, the display shows no keycodes; instead, calculations are performed as steps are saved, and the result (along with the current program step number) is seen in shortened scientific form. Unfortunately, no means to review or edit a program are provided; if a program is entered incorrectly, it needs to be reentered from the beginning.

Eighty unmerged program steps are not a heck of a lot, but they're enough (just barely!) to implement a program that calculates the Gamma functionto a precision of 7 significant digits. To use this program, you must also populate registers 4-9 with constant values:

M4=√2π
M5=68.82784822
M6=755.9596084
M7=4151.488796
M8=11399.36541
M9=12520.43913


01	STn
02	2
03	STn
04	3
05	1
06	+
07	RCLn
08	2
09	=
10	STn
11	×
12	3
13	=
14	STn
15	×
16	3
17	=
18	STn
19	×
20	3
21	=
22	STn
23	×
24	3
25	=
26	STn
27	×
28	3
29	+
30	.
31	5
32	ax
33	(
34	-
35	2ND
36	5
37	)
38	÷
39	2ND
40	ex
41	×
42	(
43	RCLn
44	4
45	×
46	RCLn
47	2
48	+
49	RCLn
50	5
51	×
52	RCLn
53	2
54	+
55	RCLn
56	6
57	×
58	RCLn
59	2
60	+
61	RCLn
62	7
63	×
64	RCLn
65	2
66	+
67	RCLn
68	8
69	×
70	RCLn
71	2
72	+
73	RCLn
74	9
75	)
76	÷
77	RCLn
78	3
79	=
80	STOP