4. Compose a C function named getSpeed that uses a reference parameter variable named speed to accept an integer argument. The function should prompt the user to enter a number in the range of 20 through 70. Set the parameter variable to zero if the user enters a number outside the range of 20 through 70.

void getSpeed(int& speed)  

//the function with reference parameter speed and & denote a reference

{  //prompts user to enter a number

 cout << "Enter a number in the range of 20 through 70: ";

 cin >> speed;  //reads the value entered by user

 if(speed < 20 || speed> 70)  

// if value of speed entered by user is outside the given range

 {

   speed = 0;  // speed is set to 0

 } }

Explanation:

In order to check how this function works you can write a main function and print the value of speed as following:

int main()

{ int speed;

   getSpeed(speed); //calls getSpeed function

   cout<<"speed is "<<speed; } //displays value of speed

Output:

Enter a number in the range of 20 through 70: 50

speed is 50

Output for if condition:

Enter a number in the range of 20 through 70: 80

speed is 0