# isfinite() function in C++

The isfinite() function is a builtin function in C++ and is used to determine whether a given value if finite or not. A finite value is a value that is neither infinite nor NAN. If the number is finite then the function returns 1 else returns zero.

Syntax:

```bool isfinite(float x);

or,
bool isfinite(double x);

or,
bool isfinite(long double x);
```

Parameter: This function takes only one parameter . It represents the floating point number.

Returns: If the number is infinite or NAN then it returns 0 else if it is finite then it returns 1.

Below programs illustrate the isfinite() function in C++:
Program 1:

 `// C++ program to illutrate the ` `// isfinite() function. ` ` `  `#include ` `using` `namespace` `std; ` ` `  `int` `main() ` `{ ` `    ``float` `x = 19.0; ` `     `  `    ``cout<<``"The value of x is = "``<< x << endl; ` ` `  `    ``// Here function check whether 19 is finite or not ` `    ``// if yes function returns 1, else 0 ` `    ``cout<<``"isfinite(x) = "``<

Output:

```The value of x is = 19
isfinite(x) = 1
```

Program 2:

 `// C++ program to illutrate the ` `// isfinite() function ` ` `  `#include ` `using` `namespace` `std;  ` ` `  `int` `main()  ` `{  ` `    ``float` `x=9.6/0.0;  ` `     `  `    ``cout<<``"The value of x is = "``<< x << endl;  ` `     `  `    ``cout<<``"isfinite(x) = "``<

Output:

```The value of x is = inf
isfinite(x) = 0
```

Program 3:

 `// C++ program to illutrate the ` `// isfinite() function ` ` `  `#include ` `using` `namespace` `std; ` ` `  `int` `main() ` `{    ` `    ``// Value is NAN ` `    ``double` `x=0.0/0.0;  ` `     `  `    ``cout<<``"Value of x is = "``<< x << endl; ` `     `  `    ``cout<<``"isfinite(x) = "``<

Output:

```Value of x is = -nan
isfinite(x) = 0
```

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