prg5.c

#include<stdio.h>
#include<pthread.h>
#include<semaphore.h>
sem_t mutex,writeblock;
int data=0,rcount=0;
void *reader(void *arg)
{
    int f;
    f=((int)arg);
    sem_wait(&mutex);
    rcount=rcount+1;
    if(rcount==1)
    sem_wait(&writeblock);
    sem_post(&mutex);
    printf("data read by reader %d is %d\n",f,data);
    sleep(1);
    sem_wait(&mutex);
    rcount=rcount-1;
    if(rcount==0)
    sem_post(&writeblock);
    sem_post(&mutex);
}
void  *writer(void *arg)
{
    int f;
    f=((int)arg);
    sem_wait(&writeblock);
    data++;
    printf("data written by writer %d is %d \n",f,data);
    sleep(1);
    sem_post(&writeblock);
}
main()
{
    int i,b;
    pthread_t rtid[5],wtid[5];
    sem_init(&mutex,0,1);
    sem_init(&writeblock,0,1);
    for(i=0;i<=2;i++)
    {
        pthread_create(&wtid[i],NULL,writer,(void*)i);
        pthread_create(&rtid[i],NULL,reader,(void*)i);
    }
    for(i=0;i<=2;i++)
    {
        pthread_join(wtid[i],NULL);
        pthread_join(rtid[i],NULL);
    }
}