Midterm, CMSC 4000, Spring 2026

Name ______________________________________

• The weight for each question is given.
• Use as much paper as you wish, but make your answers are legible.
• Please label your answers with the question number.
• Please answer each question thoughtfully and carefully.
• Please staple this page on top of your answers.
• Answer should reflect the material presented in class.

1. [2 points Each] Define the following
   1. Operating System
   2. Kernel
   3. Multiprogramming
   4. Multiprocessing
   5. Timesharing
   
   
2. Processes
   1. [2 point] What is a process?
   2. [4 points] What is a context switch and when does it occur?
   3. [4 points] Describe the operation of the system call fork
   4. [5 points] Draw a diagram representing the following code. Label this diagram well, including each part which involves the kernel.

      
      if (fork()==0) {
          // code to perform some operation
          return 0;
      }
      wait(nullptr);
      return 0;

   
   
3. Polling vs Interrupts
   1. [6 points] Describe how a program can use polling to retrieve data.
   2. [6 points] What is an interrupt and how are interrupts involved in I/O?
   3. [6 points] Describe the advantages of interrupt driven code over polling code.
   
   
4. Timers
   1. [3 points] What is a hardware timer?
   2. [4 points] Name two uses for a hardware timer.