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Section 4: Programming 1 65
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Sample Case. Sum of First n Digits. Calculate the sum of 1 + 2 + 3 + . . . + n where n is
the x-register at the beginning.
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Switch to W/PRGM.
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Press fPRGM to clear memory.
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Key in the following steps.
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Keys
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Comment
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LBL A
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STO 8
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Preset n in R8.
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fSTK
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Clear stack.
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LBL 1
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Beginning of repeat segment.
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RCL 8
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Recall r8 to X.
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+
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Add to previous sum.
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gDSZ
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Decrement r8 (r8 — 1  R8)
and test for zero.
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GTO 1
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Repeat if r8 is not zero.
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RTN
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Stop after nth iteration.
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Calculating the Function
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Switch to RUN.
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Press
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See Displayed
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Comment
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5 A
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Sum of 1 + 2 + . . . + 5.
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20 A
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Sum of 1 + 2 + . . . + 20.
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25 A
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Sum of 1 + 2 + . . . + 25.
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