#include <windows.h>
#include <vector>
#include <lowlevelmonitorconfigurationapi.h>

#pragma comment(lib, "Dxva2.lib")

const BYTE PowerMode = 0xD6;  // VCP Code defined in VESA Monitor Control Command Set (MCCS) standard
const DWORD PowerOn = 0x01;
const DWORD PowerOff = 0x04;

// Monitor description struct
struct MonitorDesc
{
    HANDLE hdl;
    DWORD power;
};

// Monitor enumeration callback
BOOL CALLBACK MonitorEnumProc(HMONITOR hMonitor, HDC hdcMonitor, LPRECT lprcMonitor, LPARAM dwData)
{
    std::vector<MonitorDesc>* pMonitors = reinterpret_cast<std::vector<MonitorDesc>*>(dwData);

    DWORD nMonitorCount;
    if (GetNumberOfPhysicalMonitorsFromHMONITOR(hMonitor, &nMonitorCount))
    {
        PHYSICAL_MONITOR* pMons = new PHYSICAL_MONITOR[nMonitorCount];

        if (GetPhysicalMonitorsFromHMONITOR(hMonitor, nMonitorCount, pMons))
        {
            for (DWORD i = 0; i < nMonitorCount; i++)
            {
                MonitorDesc desc;
                desc.hdl = pMons[i].hPhysicalMonitor;

                pMonitors->push_back(desc);
            }
        }
        delete[] pMons;
    }
    return TRUE;
}

// Switch monitor power
void MonitorSwitch(MonitorDesc& monitor, DWORD mode)
{
    if (monitor.power == mode)
        return;

    SetVCPFeature(monitor.hdl, PowerMode, mode);
    monitor.power = mode;
}

int main()
{
    std::vector<MonitorDesc> monitors;
    EnumDisplayMonitors(NULL, NULL, &MonitorEnumProc, reinterpret_cast<LPARAM>(&monitors));

    // Init
    for (auto& monitor : monitors)
    {
        monitor.power = PowerOn;
    }

    // Here select the first one monitor as example
    MonitorDesc targetMonitor = monitors[0];

    // turn off
    if (targetMonitor.power == PowerOn)
    {
        MonitorSwitch(targetMonitor, PowerOff);
    }

    Sleep(5000);

    // turn on
    if (targetMonitor.power == PowerOff)
    {
        MonitorSwitch(targetMonitor, PowerOn);
    }
}

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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
}