Scientific notation

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 will have to use less digits than the real value.
Note: Naturally numerically calculating the value in QBasic would return the same value!
INPUT WILL accept the letter E with SINGLE or DOUBLE variables while D can only be used with DOUBLE variables.

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

Code by Ted Weissgerber

 -2.34D-15
 -.00000000000000234

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Scientific notation

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