C float Data Type

C float Data Type

In C, the float data type is used to store decimal numbers (floating-point numbers). It is commonly used when precision is needed but memory efficiency is also a concern. A float can store real numbers with fractional parts.

The float data type is widely used in C programming for scientific calculations, mathematical operations, and when precision is necessary.

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1 Storage Size of float Data Type

The storage size of a float is typically 4 bytes, though this may vary based on system architecture and compiler implementation.

Type	Storage Size
float	4 bytes

2 Values Stored by float Data Type

The float data type stores real numbers, including both positive and negative values, with decimal points. However, since it uses a limited number of bits, it has a certain degree of precision and may not store exact values for very large or very small numbers.

Example values that can be stored in float:

3.14, -0.005, 12345.6789, -987.65

float in C follows the IEEE 754 single-precision floating-point format, which consists of:

• 1-bit sign
• 8-bit exponent
• 23-bit mantissa (fraction)

Sign (1 bit)

Exponent (8 bits)

Mantissa (23 bits)

Value=(−1)^Sign×(1.Mantissa) × 2^{Exponent−127}

3 Example: Declaring and Using float Variables

Let’s see a simple program demonstrating how to declare and use float variables in C.

main.c

#include <stdio.h>

int main() {
    float num1 = 3.14;
    float num2 = -7.5;
    float sum = num1 + num2;

    printf("Number 1: %.2f\n", num1);
    printf("Number 2: %.2f\n", num2);
    printf("Sum: %.2f\n", sum);

    return 0;
}

Explanation:

1. We declare three float variables: num1, num2, and sum.
2. We assign values 3.14 and -7.5 to num1 and num2 respectively.
3. The sum of these two numbers is stored in the sum variable.
4. We use printf() with the %.2f format specifier to print the float values up to two decimal places.

Output:

Number 1: 3.14
Number 2: -7.50
Sum: -4.36

4 Checking Storage Size of float Programmatically

We can determine the storage size of float in bytes using the sizeof operator.

main.c

#include <stdio.h>

int main() {
    printf("Size of float: %lu bytes\n", sizeof(float));
    return 0;
}

Output (varies based on system architecture):

Size of float: 4 bytes

5 Minimum and Maximum Values of float

The range of values a float can store is much larger than an int but with limited precision.

Storage Size	Minimum Value	Maximum Value
4 bytes	~1.2 × 10-38	~3.4 × 1038

6 Getting Maximum and Minimum Values of float Programmatically

The maximum and minimum values of a float can be retrieved using float.h.

main.c

#include <stdio.h>
#include <float.h>

int main() {
    printf("Minimum float value: %E\n", FLT_MIN);
    printf("Maximum float value: %E\n", FLT_MAX);
    return 0;
}

Output:

Minimum float value: 1.175494E-38
Maximum float value: 3.402823E+38

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Conclusion

In this tutorial, we explored the float data type in C, including:

1. Its ability to store decimal numbers with a precision of up to 6-7 decimal digits.
2. Its typical storage size of 4 bytes.
3. How to get the storage size programmatically using sizeof().
4. The minimum and maximum values that float can store.
5. How to retrieve these values using float.h.