Q(uick)BASIC Function: EXP

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EXP

A math function that calculates the exponential function (e raised to the power of a numeric expression)

Worth knowing

Useful and cross-version information about the programming environments of QBasic and QuickBasic.

Syntax
  • EXP(numeric-expression)
  • LOG(numeric-expression)
Description/Parameter(s)
numeric-expression For EXP, a number less than or equal to 88.02969.
For LOG, any positive numeric expression.
Example
PRINT EXP(0), EXP(1) 'Output is: 1 2.718282 PRINT LOG(1), LOG(EXP(1)) 'Output is: 0 1
Syntax
  • EXP(numeric-expression)
Description/Parameter(s)

The EXP function returns e (the base of natural logarithms) to the power of x. The exponent x must be less than or equal to 88.02969. A value of x greater than 88.02969 produces an Overflow error message.

The calculation of EXP is performed in single precision by default; if the argument x is double precision, EXP is calculated in double precision.

Example

This example uses the EXP function to calculate the growth of a bacterial colony over a 15-day period. The program prompts you for an initial population and the rate of growth.

CLS ' Clear screen INPUT "Initial bacterial population"; Colony0 INPUT "Growth rate per day as a percentage of population"; Rate R = Rate / 100 : Form$ = "## ###,###,###,###" PRINT : PRINT "Day Population" FOR T = 0 TO 15 STEP 5 PRINT USING Form$; T, Colony0 * EXP(R * T) NEXT

Sample Output:

Initial bacterial population? 10000 Growth rate per day as a percentage of population? 10 Day Population 0 10,000 5 16,487 10 27,183 15 44,817

See also:

Syntax
  • EXP(x)
Description/Parameter(s)

Usage Notes

  • EXP is calculated in single precision if the exponent x is an integer or single-precision value. If you use any other numeric data type, EXP is calculated in double-precision.
  • The exponent x must be less than or equal to 88.02969 when you are using single-precision values and less than or equal to 709.782712893 when you are using double-precision values. If you use a value of x that is not within those limits, BASIC produces the error message, "Overflow."
  • The constant e is approximately equal to 2.718282.
Example

This example uses the EXP function to calculate the growth of a bacterial colony over a 15-day period. The program prompts you for an initial population and the rate of growth.

CLS 'Clear screen. INPUT "Initial bacterial population"; Colony0 INPUT "Growth rate per day as a percentage of population"; Rate R = Rate / 100: Form$ = "## ###,###,###,###" PRINT : PRINT "Day Population" FOR T = 0 TO 15 STEP 5 PRINT USING Form$; T; Colony0 * EXP(R * T) NEXT

Sample Output:

Initial bacterial population? 10000 Growth rate per day as a percentage of population? 10 Day Population 0 10,000 5 16,487 10 27,183 15 44,817

See also: