The HP-19C is a printing version of the HP-29C calculator. It was, and still remains, one of the smallest printing programmable calculators ever made. The programming model is essentially identical to that of the HP-29C, except that printer-specific instructions have been added.

A while back, I bought an HP-19C that looked like a hopeless wreck; not only were there parts missing, but the two circuit boards, which are connected by a series of pin connectors, were crushed together, with most connectors bent, some broken. After I unbent the pins and repaired most of the obvious damage, I was quite surprised to find that the calculator was electronically sound, and although its printer looked beyond repair, all calculator functions were working. Then recently, I bought a non-working HP-19C; this one was in much better shape cosmetically, but it appears to have been damaged electronically. But guess what: its printer works! So now, after some transplant surgery, I have a fully functional HP-19C in my hands, and another with broken electronics, a broken printer, a missing printer cover release latch, and a missing battery cover.

The demonstration program below is a standard implementation of the Gamma function, utilizing indirect addressing and the DSZ loop instruction. Before running the program, registers 1-7 must be populated with the constants shown. To use the program, enter the desired argument and hit GSB 0.

M1:    76.18009173
M2:    -86.50532033
M3:    24.01409824
M4:    -1.231739572
M5:    1.208650974e-3
M6:    -5.395239385e-6
M7:    √2π = 2.506628275

01  25 14 00	LBL 0
02  01		1
03  11		x-y
04  25 14 02	LBL 2
05  00		0
06  16 31	x<=y
07  14 01	GTO 1
08  12		Rv
09  21		ENTER
10  12		Rv
11  51		×
12  12		Rv
13  12		Rv
14  12		Rv
15  01		1
16  41		+
17  14 02	GTO 2
18  25 14 01	LBL 1
19  12		Rv
20  45 07	STO 9
21  11		x-y
22  45 08	STO 8
23  06		6
24  45 00	STO 0
25  01		1
26  25 14 03	LBL 3
27  55 12	RCL i
28  55 09	RCL 9
29  55 00	RCL 0
30  41		+
31  61		÷
32  41		+
33  25 45	DSZ
34  14 03	GTO 3
35  55 07	RCL 7
36  51		×
37  55 09	RCL 9
38  61		÷
39  16 32	ln
40  55 09	RCL 9
41  05		5
42  63		.
43  05		5
44  41		+
45  16 32	ln
46  55 09	RCL 9
47  63		.
48  05		5
49  41		+
50  51		×
51  41		+
52  55 09	RCL 9
53  31		-
54  05		5
55  63		.
56  05		5
57  31		-
58  25 32	ex
59  55 08	RCL 8
60  61		÷
61  25 13	RTN