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72.
What is a context switch?

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73.
When we install a new package in linux system, then

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74.
What is the output of this program?
#include<stdio.h>
#include<fcntl.h>
 
int main()
{
    pid_t fd;
    char ch;
    int count;
    fd = open("demo.c",O_RDONLY);
    do{
        count = read(fd,&ch,1);
        printf("%c",ch);
    }while(count);
    return 0;
}

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75.
What is the output of this program?
#include<stdio.h>
#include<signal.h>
#include<stdlib.h>
 
void response (int);
void response (int sig_no)
{
    printf("%s\n",sys_siglist[sig_no]);
    printf("This is singal handler\n");
}
int main()
{
    pid_t child;
    int status;
    child = fork();
    switch (child){
        case -1 :
            perror("fork");
            exit (1);
        case 0 :
            kill(getppid(),SIGKILL);
            printf("I am an orphan process because my parent has been killed by me\n");
            printf("Handler failed\n");
            break;
        default :
            signal(SIGKILL,response);
            wait(&status);
            printf("The parent process is still alive\n");
            break;
    }
    return 0;
}

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77.
What is the output of second program if we run the demo1 first and after that we run demo2 in the different terminal?
/*This is demo1.c*/
#include<stdio.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<string.h>
 
int main()
{
    int shm_id;
    char *addr;
    struct shmid_ds ds;
    shm_id = shmget((key_t)1234,10,0666|IPC_CREAT);
    if(shm_id == -1){
        perror("shmget");
    }
    addr = (char*)shmat(shm_id,NULL,SHM_RND);
    if(addr == (char *)-1){
        perror("shmat");
    }
    strcpy(addr,"Example");
    if (shmdt(addr) != 0){
        perror("shmdt");
    }
    if( shmctl(shm_id,IPC_RMID,0) == -1){
           perror("shmctl");
    }
    return 0;
}
/*This is demo2.c*/
#include<stdio.h>
#include<sys/ipc.h>
#include<sys/shm.h>
 
int main()
{
    int shm_id;
    char *addr;
    struct shmid_ds ds;
    shm_id = shmget((key_t)1234,10,0666|IPC_CREAT);
    if(shm_id == -1){
        perror("shmget");
    }
    addr = (char*)shmat(shm_id,NULL,SHM_RND);
    if(addr == (char *)-1){
        perror("shmat");
    }
    printf("%s\n",addr);
    if (shmdt(addr) != 0){
        perror("shmdt");
    }
    return 0;
}

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79.
What is the output of this program?
#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
 
int main()
{
    int fd, count;
    char ch, *buff;
    buff = (char *)malloc(sizeof(char)*10);
    fd = open("demo.c",O_RDONLY);
    count = read(fd,buff,5);
    printf("%d\n",count);
    return 0;
}

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