#include<iostream>
#include <string>
using namespace std;

/*
Problem P3.13 from the textbook

Use following code to accept inputs
cout << "Enter a year between 0 and 2050: ";
cin >> <Var1>;
cout << <Var1> << endl;

Use following code to output 
cout << "The year in roman numerals: " << <Values> << endl;

*/


int main() {
// insert program here
  int year;
  int thousands;
  int hundreds;
  int tens;
  int ones;
  
  cout << "Enter a year between 0 and 2050: ";
  cin >> year;
  cout << year << endl;
  
  thousands = year/1000;
  hundreds = (year%1000)/100;
  tens = ((year%1000)%100)/10;
  ones = (((year%1000)%100)%10)/1;
  
  cout << "The year in roman numerals: ";

 if (thousands ==1){
   cout << "M";
 }
 else if (thousands == 2){
   cout << "MM";
 }
 if(hundreds == 1){
   cout << "C";
 }
 else if (hundreds==2){
   cout << "CC";
 }
  else if (hundreds==3){
   cout << "CCC";
  }
   else if (hundreds==4){
   cout << "CD";
   }
   else if (hundreds==5){
   cout << "D";
   }
   else if (hundreds==6){
   cout << "DC";
   }
   else if (hundreds==7){
   cout << "DCC";
   }
   else if (hundreds==8){
   cout << "DCCC";
   }
   else if (hundreds==9){
   cout << "CM";
   }
   if (tens == 1){
     cout << "X";
   }
   else if (tens==2){
     cout << "XX";
   }
   else if (tens==3){
     cout << "XXX";
   }
   else if (tens==4){
     cout << "XL";
   }
   else if (tens==5){
     cout << "L";
   }
   else if (tens==6){
     cout << "LX";
   }
   else if (tens==7){
     cout << "LXX";
   }
   else if (tens==8){
     cout << "LXX";
   }
   else if (tens==9){
     cout << "XC";
   }
   if (ones == 1){
     cout << "I";
   }
   else if (ones==2){
     cout << "II";
   }
   else if (ones==3){
     cout << "III";
   }
   else if (ones==4){
     cout << "IV";
   }
   else if (ones==5){
     cout << "V";
   }
   else if (ones==6){
     cout << "VI";
   }
   else if (ones==7){
     cout << "VII";
   }
   else if (ones==8){
     cout << "VIII";
   }
   else if (ones==9){
     cout << "IX";
   }
   return 0;
}
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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}