#include<iostream>
#include<stdio.h>
using namespace std;
//  mon=1
char* months[13]={" ", "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
 int mon[13];

int main(){
    void display(int, int, int);
    int weekday(int, int);
    int year,month, wd;
    char key;
    mon[0]=0; mon[1]=31; mon[2]=28; mon[3]=31; mon[4]=30; mon[5]=31; mon[6]=30; 
    mon[7]=31; mon[8]=31; mon[9]=30; mon[10]=31; mon[11]=30; mon[12]=31;

    cout<<"Enter the year: ";
    cin>>year;
    cout<<"Enter the month: ";
    cin>>month;
    
    while(1)
    {
        wd=weekday(month, year);
        display(month, year, wd);
        cout<<"\n\t up_arrow - for previous month \n\t down_arrow - for next month \n\t esc - quit\n";
        key= getch();
        if(key==27){
            cout<<"\nEND\n";
            break;
        }
        else if(key==72){
            month--;
            if(month==0){
                year--;
                month=12;
            }
        }
        else if(key==80){
            month++;
            if(month==13){
                year++;
                month=1;
            }
        }
    }
}

    void display(int month, int year, int wd){
    cout<<"\n\tcalender - "<<months[month]<<"\t"<<year;
    cout<<"\n\n| Sun | Mon | Tue | Wed | Thu | Fri | Sat |";
    cout<<"\n";
    
    int d=0;
    while(d<wd){
        cout<<"|     ";
        d++; 
    }
    int day=1;
    while(day<=mon[month]){
        cout<<"|  "<<day;
        if(day<10){
            cout<<"  ";
        }
        else{
            cout<<" ";
        }
        day++;
        d++;
        if(d==7){
            cout<<"|\n";
            d=0;
        }
    }
    cout<<"\n";
    }

    int weekday(int month, int year){
    long int total_day= 0;
    int y=1900;
    int m=1;
    while(y<year)
    {
        if(y % 4 == 0){
            total_day=total_day + 366;
        }
        else{
            total_day= total_day + 365;
        }
        y++;
    }
    while(m<month)
    {
        if(m==1 || m==3 || m==5 || m==7 || m==8)
            total_day=total_day+31;
        else if(m==2){
            if(year%4==0){
                total_day=total_day+29;
            }
            else{
                total_day=total_day+28;
            }
        }
        else
            total_day=total_day+30;
        m++;
    }
    int day_found= total_day%7; 
    cout<<"the first day is "<<day_found<<"\n";
    return day_found;
    }

C++ Online Compiler

Write, Run & Share C++ code online using OneCompiler's C++ online compiler for free. It's one of the robust, feature-rich online compilers for C++ language, running on the latest version 17. Getting started with the OneCompiler's C++ compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C++ and start coding!

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
}