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Appendix A
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Design Concepts
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The HP-80 uses the most efficient way known to computer science for evaluating mathematical expressions: (1 ) the operational stack and (2) reverse “Polish” (Lukasiewicz) notation.
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Operational Stack
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The four temporary memory locations (number registers)—arranged in the form of a “stack”—-are called X, Y, Z, and T, respectively.
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Operational Stack
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To avoid confusion between the name of a register and
its contents, the register is designated in this handbook by a capital
letter and the contents by a small letter. Thus x, y, z, and t are the contents of the X, Y, Z, and T registers. |
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| Contents |
Location Name |
t
z
y
x |
T
Z
Y
X |
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| NOTE: The contents of the X location are always displayed. |
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When you key in a number, it goes into the X location—the only location displayed. When you press SAVE , this number is repeated into the Y location. At the same time y is moved up to Z and z is moved up to T like this:
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| Press |
Contents |
Location |
| SAVE |
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