c++——参数传递

 1 #include <iostream>
 2 using namespace std;
 3 // Function prototype. The parameter is a reference variable.
 4 void doubleNum(int &SrefVar);
 5 int main()
 6 {
 7     int value = 4;
 8     cout << "In main, value is " << value << endl;
 9     cout << "Now calling doubleNum..." << endl;
10     doubleNum(value);
11     cout << "Now back in main, value is "<< value << endl;
12     return 0;
13 }
14 void doubleNum (int &SrefVar)
15 {
16     SrefVar *= 2;
17 }

 1 #include <iostream>
 2 using namespace std;
 3 //Function prototypes
 4 void getNum(int &);
 5 int doubleNum(int);
 6 int main()
 7 {
 8     int value;
 9     // Call getNum to get a number and store it in value
10     getNum(value);
11     value = doubleNum(value);
12     // Display the resulting number
13     cout << "That value doubled is " << value << endl;
14     return 0;
15 }
16 void getNum(int &userNum)
17 {
18     cout << "Enter a number: ";
19     cin >> userNum;
20 }
21 int doubleNum (int number)
22 {
23     return number *2;
24 }

 1 #include <iostream>
 2 using namespace std;
 3 //Function prototypes
 4 void getNumber(int *);
 5 void doubleValue(int *);
 6 int main()
 7 {
 8     int number;
 9     //Call getNumber and pass the address of number
10     getNumber(&number);
11     // Call doubleValue and pass the address of number
12     doubleValue(&number);
13     // Display the value in number
14     cout << "That value doubled is " << number << endl;
15     return 0;
16 }
17 void getNumber(int *input)
18 {
19     cout << "Enter an integer number: ";
20     cin >> *input;
21 }
22 void doubleValue(int *val)
23 {
24     *val *= 2;
25 }