The scalbn() function in C is part of the standard math library <math.h> and is used to scale a floating-point number by an integral power of the base (2 raised to the exponent). This function is very useful while performing high-precision calculations where scaling by powers of 2 is required.

Syntax of scalbn() in C

double scalbn(double x, int exp);

Parameters of scalbn() in C

The scalbn() function in C takes the following parameters:

• x: The floating-point number to be scaled.
• exp: The power of 2 by which we want to scale the number x.

Return Value of scalbn() in C

The scalbn() function returns the result of multiplying x by 2 raised to the power of exp i.e. x * 2^exp.

Examples of scalbn() Function in C

The below examples demonstrate how we can use the scalbn() function in C language.

Input: 
double x = 1.5
int exp = 4

Output:
The result of scaling 1.50 by 2^4 is: 24.00

Example 1

The below program demonstrates how to use the scalbn() function in C.

// C Program to demonstrate the scalbn() function

#include <math.h>
#include <stdio.h>

int main()
{

    // initialize number and exponent
    double x = 1.5;
    int exp = 4;
    // call scalbn() function
    double result = scalbn(x, exp);

    // Print the result
    printf(
        "The result of scaling %.2lf by 2^%d is: %.2lf\n",
        x, exp, result);

    return 0;
}

The result of scaling 1.50 by 2^4 is: 24.00

Time Complexity: O(1)
Auxiliary Space: O(1)

Example 2

The following program demonstrates how to scale different data types in C using the scalbn() function.

// C program to demonstrate the scalbn() function for
// different data types

#include <math.h>
#include <stdio.h>

int main()
{
    double x1 = 1.5;
    float x2 = 2.5f;
    long double x3 = 3.5l;
    int n = 4;

    // scalbn function for double
    double result1 = scalbn(x1, n);

    // scalbnf function for float
    float result2 = scalbnf(x2, n);

    // scalbnl function for long double
    long double result3 = scalbnl(x3, n);

    // Print the results
    printf(
        "The result of scaling %.2lf by 2^%d is: %.2lf\n",
        x1, n, result1);
    printf("The result of scaling %.2f by 2^%d is: %.2f\n",
           x2, n, result2);
    printf(
        "The result of scaling %.2Lf by 2^%d is: %.2Lf\n",
        x3, n, result3);

    return 0;
}

The result of scaling 1.50 by 2^4 is: 24.00
The result of scaling 2.50 by 2^4 is: 40.00
The result of scaling 3.50 by 2^4 is: 56.00

Time Complexity: O(1)
Auxiliary Space: O(1)

Note: The scalbn() function in C is available in three variants to accommodate different data types: scalbn() for double, scalbnf() for float, scalbnl() for long double.