You can see the entire program gsBasic.cpp here or view it online in the standard distribution.

#include <ilsched/iloscheduler.h>
 
ILOSTLBEGIN
 
#if defined(ILO_SDXLOUTPUT)
#include "sdxloutput.h"
#endif
 
///////////////////////////////////////////////////////////////////////////////
//
// PROBLEM DEFINITION 
//
///////////////////////////////////////////////////////////////////////////////
IloModel DefineModel(const IloEnv env, IloNumVar& makespan)
{
  IloModel model(env);
  /* CREATE THE ACTIVITIES. */
  IloActivity masonry(env,   7, "masonry   ");
  IloActivity carpentry(env, 3, "carpentry ");
  IloActivity plumbing(env,  8, "plumbing  ");
  IloActivity ceiling(env,   3, "ceiling   ");
  IloActivity roofing(env,   1, "roofing   ");
  IloActivity painting(env,  2, "painting  ");
  IloActivity windows(env,   1, "windows   ");
  IloActivity facade(env,    2, "facade    ");
  IloActivity garden(env,    1, "garden    ");
  IloActivity moving(env,    1, "moving    ");
  /* ADD THE TEMPORAL CONSTRAINTS. */
  model.add(carpentry.startsAfterEnd(masonry));
  model.add(plumbing.startsAfterEnd(masonry));
  model.add(ceiling.startsAfterEnd(masonry));
  model.add(roofing.startsAfterEnd(carpentry));
  model.add(painting.startsAfterEnd(ceiling));
  model.add(windows.startsAfterEnd(roofing));
  model.add(facade.startsAfterEnd(roofing));
  model.add(facade.startsAfterEnd(plumbing));
  model.add(garden.startsAfterEnd(roofing));
  model.add(garden.startsAfterEnd(plumbing));
  model.add(moving.startsAfterEnd(windows));
  model.add(moving.startsAfterEnd(facade));
  model.add(moving.startsAfterEnd(garden));
  model.add(moving.startsAfterEnd(painting));
  /* SET THE MAKESPAN VARIABLE. */
  makespan = IloNumVar(env, 0, IloInfinity, ILOINT);
  model.add(moving.endsAt(makespan));
 
  return model;
}
 
///////////////////////////////////////////////////////////////////////////////
//
// PRINTING OF SOLUTIONS
//
///////////////////////////////////////////////////////////////////////////////
void PrintSolution(const IloSolver solver)
{
  IlcScheduler scheduler(solver);
  IloEnv env = solver.getEnv();
  for(IloIterator<IloActivity> act(env);
      act.ok();
      ++act)
    env.out() << scheduler.getActivity(*act) << endl;
  solver.printInformation();
}
 
///////////////////////////////////////////////////////////////////////////////
//
// MAIN FUNCTION
//
///////////////////////////////////////////////////////////////////////////////
 
int main()
{
  try {
    // Model
    IloEnv env;
    IloNumVar makespan;
    IloModel model = DefineModel(env, makespan);
 
    // Algorithm
    IloSolver solver(model);
    IloGoal goal = IloInstantiate(env, makespan);
    if (solver.solve(goal)) {
      PrintSolution(solver);
#if defined(ILO_SDXLOUTPUT)
      IloSDXLOutput output(env);
      ofstream outFile("gsBasic.xml");
      output.write(IlcScheduler(solver), outFile, solver.getIntVar(makespan));
      outFile.close();
#endif
    }
    else
      solver.out() << "No Solution" << endl;
 
    env.end();
    
  } catch (IloException& exc) {
    cout << exc << endl;
  }
 
  return 0;
}
 
///////////////////////////////////////////////////////////////////////////////
//
// RESULTS
//
///////////////////////////////////////////////////////////////////////////////
 
/*
   masonry    [0 -- 7 --> 7]
   carpentry  [7..11 -- 3 --> 10..14]
   plumbing   [7 -- 8 --> 15]
   ceiling    [7..12 -- 3 --> 10..15]
   roofing    [10..14 -- 1 --> 11..15]
   painting   [10..15 -- 2 --> 12..17]
   windows    [11..16 -- 1 --> 12..17]
   facade     [15 -- 2 --> 17]
   garden     [15..16 -- 1 --> 16..17]
   moving     [17 -- 1 --> 18]
*/
 

For example:

The start and end times of six activities (garden, windows, painting, roofing, ceiling, and carpentry) are not definitely set. In fact, any of these activities can execute from its latest start time to its latest end time (for example, from day 11 to day 14 in the case of carpentry) without compromising the makespan of the overall project.