Double Data Type in C

what is Double in C ?

Double is a data type in the C language. It is similar to Float, but it is more efficient and capable of handling larger and more precise decimal numbers. The Double data type is often used in scenarios requiring high precision, such as scientific calculations or handling large datasets. While Double is sufficient for most everyday coding tasks, professionals working with large data models or precision-critical applications typically prefer Double due to its efficiency and extended range.

Format Specifier for Double.

%lf is the format specifier specifically designed for the double data type in C. However, when using printf() to display a double, you can also use %f. Both work because the printf() function automatically interprets double values as float for formatting purposes.

Example.

#include <stdio.h>

int main() {

float num1 = 123456.789123;

printf("Float value: %.12f\n", num1);

double num2 = 123456.789123;

printf("Double value: %.12lf\n", num2);

return 0; }

Output.

Float value: 123456.789062500000

Double value: 123456.789123000000

Difference between Double and Float Output.

Float: Float typically uses 32 bits in the memory.

1 bit for the sign.
8 bit for the exponents.
23 bit for the mantissa (fractional part).

Double: Double use 64 bits.

1 bit for the sing.
11 bit for the exponents.
52 bit for the mantissa.

The 23 bits of mantissa in float limit the number of significant digits it can accurately represent to approximately 6–7 decimal places. On the other hand, double has 52 bits of mantissa, allowing for about 15–16 decimal places of precision.

Thus, when a number exceeds the precision limit of a float, it gets rounded or approximated, whereas a double can represent it more accurately.

Key Takeaway.

Float truncates precision due to its smaller memory allocation, while double retains more accurate information, hence the subtle difference.
When high precision is not required, float is sufficient. But for scientific computations or large-scale applications, where small differences matter, double is preferred.