text: #ifndef SYSTEM_H
  #define SYSTEM_H
  
  #include <string>
  #include <vector>
  #include <set>
  
  #include "process.h"
  #include "processor.h"
  
  class System {
   public:
    Processor& Cpu();                   // TODO: See src/system.cpp
    std::vector<Process>& Processes();  // TODO: See src/system.cpp
    float MemoryUtilization();          // TODO: See src/system.cpp
    long UpTime();                      // TODO: See src/system.cpp
    int TotalProcesses();               // TODO: See src/system.cpp
    int RunningProcesses();             // TODO: See src/system.cpp
    std::string Kernel();               // TODO: See src/system.cpp
    std::string OperatingSystem();      // TODO: See src/system.cpp
    void Update();
  
    // TODO: Define any necessary private members
   private:
    void RemoveInactiveProcesses();
    void AddNewProcesses();
    Processor cpu_ = {};
    std::vector<Process> processes_ = {};
    std::set<int> active_pids_ = {};
  };
  
  #endif