有些语言内置了对同步原语的支持，也就是监视器。有些语言没有。C语言没有。它可以在C语言中实现，但它的实现最终取决于CPU和/或操作系统。

监视器可以用C语言实现。这里有一个例子，你可以试试。

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <semaphore.h> 

struct monitor_DataType {
  sem_t OKtoRead;
  sem_t OKtoWrite;
  int readerCount; 
  int isBusyWriting;
  int readRequested; 
};

struct monitor_DataType monitor_data; 

void monitor_StartWrite() {
    if(monitor_data.isBusyWriting || monitor_data.readerCount != 0){
sem_wait(&(monitor_data.OKtoWrite));
}
  monitor_data.isBusyWriting++;    
}

void monitor_EndWrite() {
   monitor_data.isBusyWriting--;
   if(monitor_data.readRequested){
      sem_post(&(monitor_data.OKtoRead));
   } else {
     sem_post(&(monitor_data.OKtoWrite));
   }
   }

// Function that will block until read can start

void monitor_StartRead() {
    if(monitor_data.isBusyWriting){ 
       monitor_data.readRequested++;
       sem_wait(&(monitor_data.OKtoRead));
       monitor_data.readRequested--;
       }
    monitor_data.readerCount++;
    sem_post(&(monitor_data.OKtoRead));
} 

// Function to signal reading is complete
void monitor_EndRead() {
    monitor_data.readerCount--;
    if(monitor_data.readerCount == 0){
    sem_post(&(monitor_data.OKtoWrite));
    }
}

// intialize the monitor
int monitor_Initialized(){  
int returnValue = 1;
 
// Initialize the structure
monitor_data.readerCount = 0;
monitor_data.isBusyWriting = 0;
monitor_data.readRequested = 0;

// initialize the semaphores
if(sem_init(&(monitor_data.OKtoWrite), 0, 1) == 0 && 
   sem_init(&(monitor_data.OKtoRead), 0, 1) == 0){
    returnValue = 0;
} else {
  printf("Unable to initialize semaphores\n");
}
 
return returnValue;
}

// Destroys the semphores.
void monitor_Destroy(){
  sem_destroy(&(monitor_data.OKtoWrite));
  sem_destroy(&(monitor_data.OKtoRead));
}
 
int main() {
if(monitor_Initialized() == 0){
 printf("Initialized\n");
 
 monitor_StartWrite();
 printf("Writing stuffs...\n");
 monitor_EndWrite();
 monitor_StartRead();
 printf("Reading stuffs...\n");
 monitor_EndRead();
monitor_Destroy();
}
 return 0;
}