While loop problems

[sya0524]

How do i write my coding in DEV C++ using while loop for this question :

Write a program to display a number in text format. The input from user is valid if the number is 20 to 99 only. Else the program will display a message "out of range". Use a sentinel value to stop the program (example -1).

Sample output:

Enter a number: 25
Twenty five
Enter a number: 100
Out of range
Enter a number: 99
Ninety nine
Enter a number: -1
Thank you for using this system

How to write the number in text format? Do i need to use switch?

[Peter87]

You can use std::cout to display a number.

std::cout << number;