Why Does `pow(5, 2)` Return 24 in C : A Data Type Issue?

Why pow(5, 2) Returns 24: A Matter of Data Types and Rounding

In the provided C program, the pow() function is used to calculate the powers of numbers. However, when pow(5, 2) is executed, the program unexpectedly returns 24, instead of the correct result of 25. This may leave programmers bewildered, wondering why the function appears to be misbehaving.

The root of this issue lies in the data type handling within the pow() function. By default, pow() returns a double-precision floating-point number, which can hold decimal values. However, the program then assigns this double to an integer variable, effectively truncating any decimal portion. In the case of 5^2, the actual result is 24.99997 or similar, but the truncation rounds it down to 24.

To resolve this problem and obtain the correct integer result, it is necessary to explicitly round the pow() value to the nearest integer. This can be achieved by adding 0.5 to the result before assigning it to the integer variable. The following code snippet demonstrates the correction:

int answer;
answer = pow(number1, number2) + 0.5;

By adding 0.5, we effectively round the double to the nearest integer, ensuring that the result of 5^2 becomes 25 as expected.

It is important to note that this rounding technique is only suitable for cases where the result of the power calculation is guaranteed to be an integer. In situations where the result may be a non-integer (e.g., square roots), it is preferable to assign the pow() result to a double or float variable to preserve fractional values.

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