#include <Windows.h>

int ScreenWidth, ScreenHeight;
int Interval = 100;

LRESULT CALLBACK Melter(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
	switch (Msg)
	{
	case WM_CREATE:
	{
		HDC Desktop = GetDC(HWND_DESKTOP);
		HDC Window = GetDC(hWnd);

		BitBlt(Window, 0, 0, ScreenWidth, ScreenHeight, Desktop, 0, 0, SRCCOPY);
		ReleaseDC(hWnd, Window);
		ReleaseDC(HWND_DESKTOP, Desktop);

		SetTimer(hWnd, 0, Interval, 0);
		ShowWindow(hWnd, SW_SHOW);
		break;
	}
	case WM_PAINT:
	{
		ValidateRect(hWnd, 0);
		break;
	}
	case WM_TIMER:
	{
		HDC Window = GetDC(hWnd);
		int X = (rand() % ScreenWidth) - (150 / 2),
			Y = (rand() % 15),
			Width = (rand() % 150);
		BitBlt(Window, X, Y, Width, ScreenHeight, Window, X, 0, SRCCOPY);
		ReleaseDC(hWnd, Window);
		break;
	}
	case WM_DESTROY:
	{
		KillTimer(hWnd, 0);
		PostQuitMessage(0);
		break;
	}
	return 0;
	}
	return DefWindowProc(hWnd, Msg, wParam, lParam);
}

int APIENTRY WinMain(HINSTANCE Inst, HINSTANCE Prev, LPSTR Cmd, int showcmd)
{
	// Get the width & height of current display
	ScreenWidth = GetSystemMetrics(SM_CXSCREEN);
	ScreenHeight = GetSystemMetrics(SM_CYSCREEN);

	WNDCLASS wndClass = { 0, Melter, 0,0, Inst, 0, LoadCursorW(0, IDC_ARROW), 0, 0, L"ScreenMelter" };
	
	if (RegisterClass(&wndClass))
	{
		// Create the "melter" overlapping window.
		HWND hWnd = CreateWindowExA(WS_EX_TOPMOST, "ScreenMelter", 0, WS_POPUP,
			0, 0, ScreenWidth, ScreenHeight, HWND_DESKTOP, 0, Inst, 0);
		if (hWnd)
		{
			// seed for randomization
			srand(GetTickCount());
			MSG Msg = { 0 };
			// Run the melter loop
			while (Msg.message != WM_QUIT)
			{
				if (PeekMessage(&Msg, 0, 0, 0, PM_REMOVE))
				{
					TranslateMessage(&Msg);
					DispatchMessage(&Msg);
				}
			}
		}
	}
	return 0;
}
by

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
}