#include <GL/glut.h>
#include <math.h>
#include <time.h>
#include <sys/timeb.h>



const float clockR    = 80.0f,
            clockVol  = 100.0f,

            angle1min = M_PI / 30.0f,

            minStart  = 0.9f,
            minEnd    = 1.0f,

            stepStart = 0.8f,
            stepEnd   = 1.0f;

float angleHour = 0,
      angleMin  = 0,
      angleSec  = 0;



void newLine(float rStart, float rEnd, float angle){
  float c = cos(angle), s = sin(angle);
  glVertex2f( clockR*rStart*c, clockR*rStart*s);
  glVertex2f( clockR*rEnd*c, clockR*rEnd*s);
}



void RenderScene(void){
  int i;

  glClear(GL_COLOR_BUFFER_BIT);

  glColor3f(1.0f, 0.0f, 0.0f);
  glLineWidth(2.0f);
  glEnable(GL_LINE_SMOOTH);
  glEnable(GL_POINT_SMOOTH);
  glEnable(GL_POLYGON_SMOOTH);

  glBegin(GL_LINES);
    for(i=0; i<60; i++){
      if(i%5){ 
        if(i%5 == 1)
          glColor3f(1.0f, 1.0f, 1.0f);
        newLine(minStart, minEnd, i*angle1min);
      }else{
        glColor3f(1.0f, 0.0f, 0.0f);
        newLine(stepStart, stepEnd, i*angle1min);
      }
    }
  glEnd();

  glLineWidth(3.0f);
  glBegin(GL_LINES);
    newLine(0.0f, 0.5f, -angleHour+M_PI/2);
    newLine(0.0f, 0.8f, -angleMin+M_PI/2);
  glEnd();

  glLineWidth(1.0f);
  glColor3f(0.0f, 0.0f, 1.0f);
  glBegin(GL_LINES);
    newLine(0.0f, 0.8f, -angleSec+M_PI/2);
  glEnd();

  glutSwapBuffers();
}

void SetupRC(void){
  glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
}


void ChangeSize(GLsizei w, GLsizei h){
  GLfloat aspectRatio;

  if(h == 0)
    h = 1;

  
  glViewport(0, 0, w, h);

  
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();

  
  aspectRatio = (GLfloat)w / (GLfloat)h;
  if (w <= h)
    glOrtho (-clockVol, clockVol, -clockVol / aspectRatio, clockVol / aspectRatio, 1.0, -1.0);
  else
    glOrtho (-clockVol * aspectRatio, clockVol * aspectRatio, -clockVol, clockVol, 1.0, -1.0);

  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}


void TimerFunction(int value)
{
  struct timeb tb;
  time_t tim=time(0);
  struct tm* t;
  t=localtime(&tim);
  ftime(&tb);

  angleSec = (float)(t->tm_sec+ (float)tb.millitm/1000.0f)/30.0f * M_PI;
  angleMin = (float)(t->tm_min)/30.0f * M_PI + angleSec/60.0f;
  angleHour = (float)(t->tm_hour > 12 ? t->tm_hour-12 : t->tm_hour)/6.0f * M_PI+
              angleMin/12.0f;

  glutPostRedisplay();
  glutTimerFunc(33,TimerFunction,1);
}
// Main program entry point
int main(int argc, char* argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
  glutCreateWindow("glClock by bobo");

  glutDisplayFunc(RenderScene);
  glutReshapeFunc(ChangeSize);
  glutTimerFunc(33, TimerFunction, 1);

  SetupRC();

  glutMainLoop();

  return 0;
}

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
}