# Difference between revisions of "Scientific notation"

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− | * '''E''' denotes [[SINGLE]] precision accuracy and '''D''' denotes [[DOUBLE]] precision accuracy in Qbasic. | + | * '''E''' denotes [[SINGLE]] precision accuracy and '''D''' denotes [[DOUBLE]] precision accuracy in Qbasic. D and E are considered numbers! |

* To translate the notation, multiply the number preceding the letter by the value of 10 raised to the power following the letter. | * To translate the notation, multiply the number preceding the letter by the value of 10 raised to the power following the letter. | ||

* [[PRINT USING]] can display the normal numerical values. You may have to use less digits. | * [[PRINT USING]] can display the normal numerical values. You may have to use less digits. | ||

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{{Cl|FUNCTION}} StrNum$ (n#) | {{Cl|FUNCTION}} StrNum$ (n#) | ||

− | value$ = {{Cl|LTRIM$}}({{Cl|STR$}}(n#)) | + | value$ = {{Cl|UCASE$}}({{Cl|LTRIM$}}({{Cl|STR$}}(n#))} |

− | Xpos% = {{Cl|INSTR}}(value$, "D") + {{Cl|INSTR}}(value$, "E") | + | Xpos% = {{Cl|INSTR}}(value$, "D") + {{Cl|INSTR}}(value$, "E") 'only D or E can be present |

{{Cl|IF}} Xpos% {{Cl|THEN}} | {{Cl|IF}} Xpos% {{Cl|THEN}} | ||

expo% = {{Cl|VAL}}({{Cl|MID$}}(value$, Xpos% + 1)) | expo% = {{Cl|VAL}}({{Cl|MID$}}(value$, Xpos% + 1)) | ||

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{{Cl|END FUNCTION}} '' '' | {{Cl|END FUNCTION}} '' '' | ||

{{CodeEnd}} | {{CodeEnd}} | ||

+ | {{small|Code by Ted Weissgerber}} | ||

{{OutputStart}} | {{OutputStart}} | ||

-2.34D-15 | -2.34D-15 |

## Revision as of 23:43, 11 November 2010

**Scientific notation** or exponential notation is used to express very large or small numerical values by SINGLE or DOUBLE accuracy.

*Usage:* -9.7587E+04 or 4.6545D-9

**E**denotes SINGLE precision accuracy and**D**denotes DOUBLE precision accuracy in Qbasic. D and E are considered numbers!- To translate the notation, multiply the number preceding the letter by the value of 10 raised to the power following the letter.
- PRINT USING can display the normal numerical values. You may have to use less digits.
**Note:**Naturally numerically calculating the value in Qbasic would return the same value!

*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 ).

- To multiply by 10 raised to a positive power, just move the decimal point to the right by 3.
- The result is 2184 in DOUBLE accuracy.

*Sample 2:* -5.412D-2 is negative 5.412 times .01 (10 raised to the -2 power or 10 ^ -2 ).

- To multiply a number by 10 raised to a negative power, just move the decimal point to the left by 2.
- The result is -.05412 in DOUBLE accuracy.

*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).

- To multiply a number by 10 raised to a positive power, just move the decimal point to the right by 12.
- The result is 3,070,000,000,000 in SINGLE accuracy.

*Example:* A string function that displays extremely small or large exponential decimal values.

* *
num# = -2.34D-15
PRINT num#
PRINT StrNum$(num#)
END
FUNCTION StrNum$ (n#)
value$ = UCASE$(LTRIM$(STR$(n#))}
Xpos% = INSTR(value$, "D") + INSTR(value$, "E") 'only D or E can be present
IF Xpos% THEN
expo% = VAL(MID$(value$, Xpos% + 1))
IF VAL(value$) < 0 THEN
sign$ = "-": valu$ = MID$(value$, 2, Xpos% - 2)
ELSE valu$ = MID$(value$, 1, Xpos% - 1)
END IF
dot% = INSTR(valu$, "."): L% = LEN(valu$)
IF expo% > 0 THEN add$ = STRING$(expo% - (L% - dot%), "0")
IF expo% < 0 THEN min$ = STRING$(ABS(expo%) - (dot% - 1), "0"): DP$ = "."
FOR n = 1 TO L%
IF MID$(valu$, n, 1) <> "." THEN num$ = num$ + MID$(valu$, n, 1)
NEXT
ELSE StrNum$ = value$: EXIT FUNCTION
END IF
StrNum$ = sign$ + DP$ + min$ + num$ + add$
END FUNCTION * *

-2.34D-15 -.00000000000000234

*See also:*

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