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76 lines
2.6 KiB
Markdown
76 lines
2.6 KiB
Markdown
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**Scientific notation** or [^](^) notation is used to express very large or small numerical values by [SINGLE](SINGLE) or [DOUBLE](DOUBLE) accuracy.
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## Usage
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> -9.7587E+04 or 4.6545D-9
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* **E** denotes [SINGLE](SINGLE) precision accuracy and **D** denotes [DOUBLE](DOUBLE) precision accuracy in QBasic. D and E are considered numbers!
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* To translate the notation, multiply the number preceding the letter by the value of 10 raised to the power following the letter.
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* [PRINT USING](PRINT-USING) can display the normal numerical values. You will have to use less digits than the real value.
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* **Note:** Naturally numerically calculating the value in QBasic would return the same value!
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* [INPUT](INPUT) WILL accept the letter E with [SINGLE](SINGLE) or [DOUBLE](DOUBLE) variables while D can only be used with [DOUBLE](DOUBLE) variables.
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*Sample 1:* +2.184D+3 means to multiply 2.184 by 1,000 (1,000 is 10 raised to the third power, or 10 [^](^) 3 ).
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> To multiply by 10 raised to a positive power, just move the decimal point to the right by 3.
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> The result is 2184 in DOUBLE accuracy.
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*Sample 2:* -5.412D-2 is negative 5.412 times .01 (10 raised to the -2 power or 10 [^](^) -2 ).
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> To multiply a number by 10 raised to a negative power, just move the decimal point to the left by 2.
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> The result is -.05412 in DOUBLE accuracy.
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*Sample 3:* 3.07E+12 is a positive 3.07 times 1,000,000,000,000 (10 raised to the 12 power or 10 [^](^) 12).
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> To multiply a number by 10 raised to a positive power, just move the decimal point to the right by 12.
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> The result is 3,070,000,000,000 in SINGLE accuracy.
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## Example(s)
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A string function that displays extremely small or large exponential decimal values.
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```vb
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num# = -2.34D-15
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PRINT num#
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PRINT StrNum$(num#)
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END
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FUNCTION StrNum$ (n#)
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value$ = UCASE$(LTRIM$(STR$(n#)))
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Xpos% = INSTR(value$, "D") + INSTR(value$, "E") 'only D or E can be present
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IF Xpos% THEN
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expo% = VAL(MID$(value$, Xpos% + 1))
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IF VAL(value$) < 0 THEN
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sign$ = "-": valu$ = MID$(value$, 2, Xpos% - 2)
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ELSE valu$ = MID$(value$, 1, Xpos% - 1)
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END IF
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dot% = INSTR(valu$, "."): L% = LEN(valu$)
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IF expo% > 0 THEN add$ = STRING$(expo% - (L% - dot%), "0")
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IF expo% < 0 THEN min$ = STRING$(ABS(expo%) - (dot% - 1), "0"): DP$ = "."
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FOR n = 1 TO L%
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IF MID$(valu$, n, 1) <> "." THEN num$ = num$ + MID$(valu$, n, 1)
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NEXT
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ELSE StrNum$ = value$: EXIT FUNCTION
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END IF
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StrNum$ = sign$ + DP$ + min$ + num$ + add$
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END FUNCTION
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```
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<sub>Code by Ted Weissgerber</sub>
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```text
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-2.34D-15
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-.00000000000000234
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```
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## See Also
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* [^](^)
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* [SINGLE](SINGLE), [DOUBLE](DOUBLE)
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