1. True or False:

• A child process has the same address space as its parent.

• In a parent process, the wait() call blocks until at least one child signals the parent with its exit status.

• It is possible that a parent process exits before its child process finishes.

• In a parent process a wait call always blocks.

• A process running in the background cannot be killed.

• File descriptor are inherited across both fork and exec calls.

• A child process whose parent calls wait cannot become a zombie.

• You can send a signal to a process you do not own.

//F

• You can send a signal to a process that is not related to the process sending the signal.

//F

• The function htonl() is used to convert a string to a port number.

// CONVERT NUMBER to NUMBER

• The bind call associaes a port number with the server process.

// ASSOCIATE SOCKET FD to SERVER ADDR

• When a process running in the background writes to stdout, the output appears on the screen.

// this is how > &1 worked.

3.

int main(){
    if (fork()==0){
        if (fork()==0){
            fprintf(stderr, "A");
            exit(3);
        }else{
            fprintf(stderr, "B");
            exit(2);
        }
    }else{
        int status;
        fprintf(stderr, "C");
        if (wait(&status) != -1){
            if (WIFEXITED(status)){
                fprintf(stderr, "%d", WEXITSTATUS(status));
            }
        }
        fprintf(stderr, "D");
    }
    fprintf(stderr, "E");
    return 0;
}

3(a). How Many processes including the original one are created?

3(b). Write all possible output orders:

3(c). Is it possible for a child process in this program to ever become an orphan? Explain: ANSWER : 3; ABC2DE, ACB2DE, BAC2DE, BCA2DE, CAB2DE, CBA2DE; Yes, the child of child could run slow and the original and first child could terminate first.

4.

int main(){
    int var = 1;
    int status;
    int r = fork();

    if (r==0){ // process X
        var++;
        r = fork();
        if (r==0){
            var ++;
            exit(var);} 
        else { // process Y
            if (wait(&status) != -1) {
                if (WIFEXITED(status)){
                    printf("A %d\n", WEXITSTATUS(status));}
            }
            var += 2;
        }}
    else{ // process Z
        printf("W %d\n", var);
        if (wait(&status) != -1){
            if (WIFEXITED(status)){
                printf("B %d\n", WEXITSTATUS(status));}
        }

    }
    printf("C %d\n", var);
    return 0;
}

4(a). Write all possible output orders for this program.

 W 1;A 3;C 4; B 0;C 1
 A 3;C 4;W 1; B 0;C 1
 A 3;W 1;C 4; B 0;C 1

4(b). Can process X or Y become an orphan? No

4(c). Can process X or Y become an zombie? It can be before wait() call clear the process table. (孩子结束的太快)

5.