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Display Control
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In the HP-67, you can select many different rounding options for display of numbers.
When you first turn on the HP-67, for example, the calculator “wakes
up” with numbers appearing rounded to two decimal places. Thus, the fixed constant
π, which is actually in the calculator as 3.141592654, will appear in the
display as 3.14 (unless you tell the calculator to display the number rounded to
a greater or lesser number of decimal places).
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Although a number is normally shown to only two decimal places, the HP-67 always
computes internally using each number as a 10-digit mantissa and a two-digit exponent
of 10. For example, when you compute 2 × 3, you see the answer to only
two decimal places:
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Press
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Display
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2  ENTER 3 ×
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However, inside the calculator all numbers have 10-digit mantissas and two-digit
exponents of 10. So the HP-67 actually calculates using full 10-digit numbers:
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2.000000000 × 1000 ENTER 3.000000000 × 1000 ×
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yields an answer that is actually carried to full 10 digits internally:
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6.000000000 × 1000
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You see only these digits...
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these digits are also present.
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