Calculator Example

The following specifications have been derived from the instructions printed on the back of the calculator. (Image from http://www.hpmuseum.org/hp35.htm.)

Low battery lights all decimal points.

eg.Calculator
volts	watts()	points()
3.75	.500	false
3.60	.500	false
3.45	.500	false
3.30	.500	true

Improper operations flash display. Press clx.

eg.Calculator
key	x()	flash()
100	100	false
enter	100	false
0	0	false
/	0	true
clx	0	false

clx clears the display.

eg.Calculator
key	x()	y()	z()	t()
100	100
enter	100	100
enter	100	100	100
enter	100	100	100	100
clx	0	100	100	100

clr clears all registers.

eg.Calculator
key	x()	y()	z()	t()
100	100
enter	100	100
enter	100	100	100
enter	100	100	100	100
clr	0	0	0	0

chs changes sign of display. May be used as the first entry when entering negative numbers.

eg.Calculator
key	x()	y()
100	100	0
chs	-100	0
chs	100	0
enter	100	100
chs	-0	100
100	-100	100

eex causes next entries to become the exponent of x. For negative expoinents chs must precede digits.

The operational stack consistes of four registers (x, y, z and t). A fifth register (s) is used for constant storage.

The stack is automatically raised by an entry into x or by rcl unless the entry or rcl immediately follows clx, sto or enter.

Follwing any trig function z is duplicated into register t.

All angles are in degrees.

Example (2+3) * (4/5) / sin(30) * (4^-1.5) = 1.0000

eg.Calculator
key	x()	y()
2	2
enter	2	2
3	3	2
+	5
4	4	5
*	20
5	5	20
/	4
30	30	4
sin	.5	4
/	6
-1.5	-1.5	8
enter	-1.5	-1.5
4	4	-1.5
x^y	.125	8
*	1.0000

You can run this document as it stands right now against a calculator implemented at c2.com. You will find that that the tests, the fixture and the calculator code are all not yet complete. Failing tests turn a cell red. There are two values in the cell. The top one is the expected result. The bottom is the actual result.

• http:run.cgi -- invoke on c2.com and view results here
• http:run.log -- view stderr output from last run
• http:run.txt -- view cgi handler that does remote test invocation

• http://home.c2.com/~ward/hp35.cgi -- machine generated test data
• http:Release/Source/eg/Calculator.java -- the HP35 calculator and its fixture