Question

OPERATING SYSTEMS QUESTION:

Given the code below:    
int  main()  
{     
   pid_t  pid;
   int value = 10;
   pid = fork();     
   if (pid == 0) {  /* child */            
      value += 8;             
      printf(“CHILD: value = %d\n”, value);  /* Line A */            
      exit(0);     
   } else { /* parent */           
      value += 5;      
      wait(NULL);           \
      printf(“PARENT: value = %d\n”, value);  /* Line B */           
      exit(0);     
   }
}  

What is printed at Line B? Explain why in a few sentences.

Answer 1

Solution:

​​​​​​When we use fork() the new child process was created. so there are two different processes running in a program. Parent process and child process.

If the Child process created successfully it returns the value zero.

Explanation:

We assigned the 10 to the variable named value by using int value = 10 statement.

In the below code we create a single child process by using the statement pid = fork().  

Hence there are two different processes running in the program.

Initially value is 10 for the parent process. The parent process does not have the pid 0. Hence it executes else part the 5 was added with the value variable and it becomes 15. Hence parent value is 15.

Initially value is 10 for the child process. The child process has the pid 0. Hence it executes if part the 8 was added with the value variable and it becomes 18. Hence child value is 18.