C++ Tutorial/Operators statements/switch

A Help system that process multiple requests.

<source lang="cpp">#include <iostream> using namespace std;

int main() {

 char choice;  
 
 for(;;) {  
   do {  
     cout << "Help on:\n";  
     cout << "  1. if\n";  
     cout << "  2. switch\n";  
     cout << "  3. for\n";  
     cout << "  4. while\n";  
     cout << "  5. do-while\n";  
     cout << "  6. break\n";  
     cout << "  7. continue\n";  
     cout << "  8. goto\n";  
     cout << "Choose one (q to quit): ";  
     cin >> choice;  
   } while( choice < "1" || choice > "8" && choice != "q");  
 
   if(choice == "q") break;  
 
   cout << "\n\n";  
  
   switch(choice) {  
     case "1":  
       cout << "The if:\n\n";  
       break;  
     case "2":  
       cout << "The switch:\n\n";  
       break;  
     case "3":  
       cout << "The for:\n\n";  
       break;  
     case "4":  
       cout << "The while:\n\n";  
       break;  
     case "5":  
       cout << "The do-while:\n\n";  
       break;  
     case "6":  
       cout << "The break:\n\n";  
       break;  
     case "7":  
       cout << "The continue:\n\n";  
       break;  
     case "8":  
       cout << "The goto:\n\n";  
       break;  
   }  
   cout << "\n";  
 }  
 
 return 0;  

}</source>

Help on:
  1. if
  2. switch
  3. for
  4. while
  5. do-while
  6. break
  7. continue
  8. goto
Choose one (q to quit): 4

The while:

Help on:
  1. if
  2. switch
  3. for
  4. while
  5. do-while
  6. break
  7. continue
  8. goto
Choose one (q to quit): 2

The switch:

Help on:
  1. if
  2. switch
  3. for
  4. while
  5. do-while
  6. break
  7. continue
  8. goto
Choose one (q to quit): q

A switch without break statements.

<source lang="cpp">#include <iostream> using namespace std;

int main() {

 int i; 

 for(i=0; i<5; i++) { 
   switch(i) { 
     case 0: cout << "less than 1\n"; 
     case 1: cout << "less than 2\n"; 
     case 2: cout << "less than 3\n"; 
     case 3: cout << "less than 4\n"; 
     case 4: cout << "less than 5\n"; 
   } 
   cout << "\n"; 
 } 

 return 0; 

}</source>

less than 1
less than 2
less than 3
less than 4
less than 5
less than 2
less than 3
less than 4
less than 5
less than 3
less than 4
less than 5
less than 4
less than 5
less than 5

Calculator based on switch statement

<source lang="cpp">#include <iostream> int result; char oper_char; int value; int main() {

   result = 0;                
   while (true) {
      std::cout << "Result: " << result << "\n";
      std::cout << "Enter operator and number: ";
   
      std::cin >> oper_char >> value;
   
      if ((oper_char == "q") || (oper_char == "Q"))
          break;
   
      switch (oper_char) {
          case "+":
              result += value;
              break;
          case "-":
              result -= value;
              break;
          case "*":
              result *= value;
              break;
          case "/":
              if (value == 0) {
                  std::cout << "Error:Divide by zero\n";
                  std::cout << "   operation ignored\n";
              } else
                  result /= value;
              break;
          default:
              std::cout << "Unknown operator " << oper_char << "\n";
              break;
      }
   }
   return (0);

}</source>

char navigation based on switch

<source lang="cpp">#include <iostream> using namespace std;

int main() {

 char choice; 

 cout << "Help on:\n"; 
 cout << "  1. if\n"; 
 cout << "  2. switch\n"; 
 cout << "Choose one: "; 
 cin >> choice; 

 cout << "\n"; 
 
 switch(choice) { 
   case "1": 
     cout << "The if:\n\n"; 
     break; 
   case "2": 
     cout << "The switch:\n\n"; 
     break; 
   default: 
     cout << "Selection not found.\n"; 
 } 

 return 0; 

}</source>

Help on:
  1. if
  2. switch
Choose one: 1
The if:

switch case falling through

<source lang="cpp">#include <iostream> using namespace std;

int main() {

 int i; 

 for(i=0; i<5; i++) { 
  switch(i) { 
     case 1: 
     case 2: 
     case 3:  
       cout << "i is less than 4"; 
       break; 
     case 4:  
       cout << "i is 4"; 
       break;
   }    
   cout << "\n"; 
 } 

 return 0; 

}</source>

i is less than 4
i is less than 4
i is less than 4
i is 4

switch statement based on data type

<source lang="cpp">#include <iostream.h> void increase (void* data, int type) {

 switch (type)
 {
   case sizeof(char) : (*((char*)data))++; break;
   case sizeof(short): (*((short*)data))++; break;
   case sizeof(long) : (*((long*)data))++; break;
 }

} int main () {

 char a = 5;
 short b = 9;
 long c = 12;
 increase (&a,sizeof(a));
 increase (&b,sizeof(b));
 increase (&c,sizeof(c));
 cout << (int) a << ", " << b << ", " << c;
 return 0;

}</source>

6, 10, 13"

The switch

<source lang="cpp">#include <iostream> using namespace std;

int main() {

 int num; 

 cout << "Enter a number from 1 to 3: "; 
 cin >> num; 

 switch(num) { 
   case 1:  
     cout << "111.\n"; 
     break; 
   case 2:  
     cout << "222.\n"; 
     break; 
   case 3:  
     cout << "333.\n"; 
     break; 
   default: 
     cout << "You must enter either 1, 2, or 3.\n"; 
 } 

 return 0; 

}</source>

Enter a number from 1 to 3: 2
222.