C Math log10() Function
Example
Return the base 10 logarithm of different numbers:
printf("%f", log10(120.0));
printf("%f", log10(10.0));
printf("%f", log10(3.1623));
printf("%f", log10(1.0));
printf("%f", log10(0.0));
printf("%f", log10(-1.0));
Definition and Usage
The log10() function returns the base 10 logarithm of a number.
The log10() function is defined in the <math.h> header file.
Tip: The base 10 logarithm indicates approximately how many digits the integer part of a number has. See how to use it to count digits in the example below.
Syntax
One of the following:
log10(double number);Parameter Values
| Parameter | Description |
|---|---|
| number |
Required. Specifies the value to calculate the logarithm for. If the value is negative, it returns NaN (Not a Number). If the value is 0, it returns -infinity. |
Technical Details
| Returns: | A double value representing the base 10 logarithm of
a number. |
|---|
More Examples
Example
Count the digits in a number:
double x = 1260.0;
int digits = floor( log10( x ) ) + 1;
printf("The number %f has %d digits.", x, digits);