[Term Entry] C++ Math-functions: isnormal()

Author: mamtawardhani

content/cpp/concepts/math-functions/terms/isnormal/isnormal.md

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+---
+Title: 'isnormal()'
+Description: 'Checks whether a floating-point value is a normal number (not zero, subnormal, infinite, or NaN).'
+Subjects:
+  - 'Computer Science'
+  - 'Game Development'
+Tags:
+  - 'Arithmetic'
+  - 'Functions'
+  - 'Math'
+  - 'Numbers'
+CatalogContent:
+  - 'learn-c-plus-plus'
+  - 'paths/computer-science'
+---
+
+In C++, the **`isnormal()`** function determines whether a floating-point number is normal, meaning it is non-zero, not subnormal, not infinite, and not NaN. It is useful when performing numerical computations that require standard floating-point numbers.
+
+## Syntax
+
+```pseudo
+bool isnormal(double x);
+```
+
+Or, alternatively:
+
+```pseudo
+bool isnormal(float x);
+```
+
+Or, alternatively:
+
+```pseudo
+bool isnormal(long double x);
+```
+
+**Parameters:**
+
+- `x` : The floating-point number (`float`, `double`, or `long double`) to be checked.
+
+**Return value:**
+
+- `true` if `x` is a normal floating-point number.
+- `false` if `x` is zero, subnormal, infinite, or NaN.
+
+## Example 1: Checking normal and zero numbers
+
+In this example, a normal number and zero are checked using `isnormal()`. The normal number returns `true`, while zero returns `false`:
+
+```cpp
+#include <iostream>
+#include <cmath>
+
+int main() {
+  double a = 5.0;
+  double b = 0.0;
+
+  std::cout << std::boolalpha;
+  std::cout << "isnormal(a): " << std::isnormal(a) << "\n";
+  std::cout << "isnormal(b): " << std::isnormal(b) << "\n";
+
+  return 0;
+}
+```
+
+The output of this code is:
+
+```shell
+isnormal(a): true
+isnormal(b): false
+```
+
+## Codebyte Example: Checking subnormal, infinite, and NaN numbers
+
+In this example, subnormal, infinite, and NaN numbers are checked. All of these are not considered normal, so `isnormal()` returns `false` for each:
+
+```codebyte/cpp
+#include <iostream>
+#include <cmath>
+#include <limits>
+
+int main() {
+  double subnormal = std::numeric_limits<double>::denorm_min();
+  double inf = std::numeric_limits<double>::infinity();
+  double nanVal = std::nan("");
+
+  std::cout << std::boolalpha;
+  std::cout << "isnormal(subnormal): " << std::isnormal(subnormal) << "\n";
+  std::cout << "isnormal(inf): " << std::isnormal(inf) << "\n";
+  std::cout << "isnormal(nanVal): " << std::isnormal(nanVal) << "\n";
+
+  return 0;
+}
+```
+
+## Frequently Asked Questions
+
+### 1. How to use not equal in C++?
+
+The not equal operator in C++ is written as `!=`. It compares two values and returns `true` if they are not equal, otherwise `false`. Example:
+
+```cpp
+#include <iostream>
+int main() {
+  int a = 5, b = 10;
+  if (a != b) {
+    std::cout << "a and b are not equal\n"; // outputs: a and b are not equal
+
+  }
+  return 0;
+}
+```
+
+### 2. What is `isdigit()` in C++?
+
+The `isdigit()` function checks if a character is a decimal digit (`'0'`–`'9'`). It is declared in `<cctype>` or `<ctype.h>` and returns a non-zero value (`true`) if the character is a digit, otherwise 0 (`false`).
+
+### 3. What are the four types of functions in C++?
+
+The four types of functions in C++ based on parameters and return type are:
+
+1. Function with no arguments and no return value
+2. Function with arguments and no return value
+3. Function with no arguments but returns a value
+4. Function with arguments and returns a value