CS 3750 Study Guide for Exams
COMPUTER SCIENCE 3750 -- Operating Systems I

1. What actions does an operating system perform?
   
   
2. What services does an operating system provide?
   
   
3. What forces have driven the development of operating systems?
   
   
4. List several major milestones in the development of operating systems.
   
   
5. Discuss the operation of an old-fashioned batch system.
   
   
6. Explain control cards.
   
   
7. Define "multi-processing" and "multi-programming", being careful to explain the difference between them.
   
   
8. Explain distributed systems.
   
   

1. Discuss the basic architectural components of a modern computing system, such as cache, registers, ALU, CPU, system bus, primary memory, device controllers, and hard disks. How are these elements typically structured and organized? How do they interoperate?
   
   
2. Explain interrupts and how the functioning of a modern computing system depends on interrupts.
   
   
3. Explain DMA.
   
   
4. Explain privileged mode and privileged instructions.
   
   
5. Discuss the way that the existence of two operating modes facilitates the maintenance of correct operation in a multiprogramming operating system. Be sure to include a specific example to illustrate each important point you make.
   
   
6. Discuss some important operating systems capabilities and the hardware support required to implement them.
   
   
7. Explain how system calls are implemented.
   
   

1. An operating system can be thought of as a supplier of many services to user processes, and a manager of many resources that are available to user processes. Name some of these services and resources. (Variety in your answer will count more than quantity.)
   
   
2. What is a system call? Who (what type of process) would make a system call? Who (what process) would be the callee?
   
   
3. Explain what a process is.
   
   
4. What are the services that an operating system provides in relation to:
   • Process Management
   • Main-Memory Management
   • Secondary Storage Management
   • I/O System Management
   • File Management
   • Protection
   • Networking
     
     
5. Discuss several approaches to designing an operating system.
   
   

1. Define "program" and "process", being careful to explain the difference between them.
   
   
2. What is the "state" of a process? (in the widest sense -- not the kind of state that is either "new", "active", "waiting", or "halted.") List as many components of process state as you can think of.
   
   
3. Explain processes and threads.
   
   
4. Explain process control blocks.
   
   
5. Explain ready queue and I/O queue.
   
   
6. Explain the roles of short-term and long-term schedulers.
   
   
7. Explain swapping and context switching.
   
   
8. Discuss some important Unix system calls.
   
   
9. Explain user-level versus kernel-level threads.
   
   
10. Explain the producer-consumer problem.
    
    
11. Discuss several styles of interprocess communication.
    
    

1. Explain preemptive and non-preemptive scheduling.
   
   
2. Explain shortest-job-first (SJF) scheduling. What does it achieve? When is it easy to implement, and when is it hard to implement?
   
   
3. Explain "aging." Also, what is the need for aging?
   
   
4. Explain round robin.
   
   
5. Explain symmetric multiprocessing.
   
   
6. Explain throughput, turnaround time, waiting time and response time.
   
   

1. Define "critical section" and "critical section problem". Be sure to adequately describe the context in which these concepts are important.
   
   
2. Explain the meaning of each of the following three requirements for a solution to a critical section problem:
   • a) mutual exclusion
   • b) progress
   • c) bounded waiting.
   
   
3. What is a "software solution" to a critical section problem? When we studied software solutions, what underlying assumptions did we rely upon concerning the instruction set of the machine on which our programs would execute?
   
   
4. Complete the following working definition of an atomic operation: If two processes attempt to execute an ATOMIC OPERATION concurrently, the result will be ... "
   
   
5. Explain how the "hardware" of a computer can be used to insure the atomicity of an operation such as the "wait" of a semaphore, or a "test-and-set".
   
   
6. Give a complete description of one of the following "classic problems" in process coordination:
   • a) The producer/consumer problem (bounded buffer version)
   • b) The readers/writers problem (either the first or second version)
   • c) The dining philosophers problem.
     
   (Note: I'm asking that you state one of these problems, not give a solution.)
   
   
7. Define busy waiting. How can busy waiting be avoided in the synchronization protocols of a uni-processor computer?
   
   
8. Describe the data structure "counting semaphore" (also called a "queueing semaphore"). Be sure to describe
   • the data object itself, its structure and organization from a logical standpoint,
   • the operations that are available on such a semaphore and their important characteristics, such as what they input, what they output, pre-conditions, and post-conditions. Don't forget that there are "atomicity" conditions that must be met by these operations.
   
   

1. What are the four necessary conditions for deadlock? Discuss some of the (operating system) techniques that prevent deadlock by making sure that one or more of the conditions never holds. What are some of the details and requirements of the implementation of these techniques?
   
   
2. Discuss deadlock avoidance. What is involved in the Banker's algorithm? How does an operating system use the Banker's algorithm to avoid deadlock? What is a safe sequence? If a system is not in deadlock, is it always in a safe state?
   
   
3. Describe a method by which an operating system can detect deadlock. How should this be done in a system in which there is just one instance of each resource type? What about a system in which there are multiple instances of some resource types?
   
   

1. Discuss various approaches to the management of main memory. Include fixed partitions, variable partitions, segments, and paging.
   
   
2. What are external and internal fragmentation?
   
   

1. Discuss virtual memory, and various approaches to the implementation of virtual memory.
   
   
2. Discuss implementations of page replacement.
   
   
3. Discuss the issues involved in per-process frame allocation.
   
   
4. Discuss ways of detecting and dealing with thrashing processes.
   
   
5. Discuss the issues involved in choosing a page size.
   
   

1. Describe several approaches to organizing a file system. Explain advantages and disadvantages of the various methods.
   
   
2. Discuss some of the problems inherent in maintaining a directory structure in which arbitrary multiple links to files are allowed to exist.
   
   

1. Discuss the design goals important in the choice of a data structure for representing the free space list for a magnetic disk.
   
   
2. Define contiguous, linked, and indexed file allocation methods. What kinds of file accesses are supported efficiently by each? What are some advantages and disadvantages of each? Which method suffers from the effects of external fragmentation?
   
   
3. In order to support create, open, read, write, reset (seek), and delete operations on files, what information about each file must be stored by the operating system?
   
   

1. Discuss the ways that typical device controllers interact with the CPU and other components of a modern computing system.
   
   
2. Discuss polling, interrupt driven I/O, and DMA.
   
   
3. Discuss interrupt levels.
   
   
4. Discuss block-oriented and character-oriented I/O.
   
   

1. Explain various disk scheduling policies.
   
   
2. What is involved in disk formatting?
   
   
3. Discuss swap space implementations.
   
   
4. Discuss disk striping and RAID's.
   
   

1. No questions yet.
   
   

1. Discuss various approaches to managing and coordinating multiprocessor systems. Be sure to include loosely coupled vs. tightly coupled, and master/slave organization.
   
   
2. Describe various network topologies.
   
   
3. Define the term: Distributed System.
   
   
4. What are the advantages of a distributed system?
   
   
5. Describe several popular connection topologies of distributed systems.
   
   
6. Discuss the following routing strategies: fixed routing, virtual circuits, and dynamic routing.
   
   
7. Discuss the following connection strategies: circuit switching, message switching, and packet switching.
   
   
8. Discuss CSMA/CD, token passing, and message slots as they relate to resolving contention.
   
   
9. Discuss the ISO layers.
   
   

1. Discuss computation and process migration.
   
   
2. Discuss fault-tolerance.
   
   
3. Discuss scalability.
   
   

1. Discuss processor and storage device transparency.
   
   
2. Discuss the relative merits of several distributed filesystems.
   
   

1. Why do we require a process to advance its logical clock when it receives a message whose time-stamp is greater than the current value of its logical clock?
   
   
2. Discuss ways that distribute processes can achieve mutual exclusion.
   
   
3. Discuss ways that distributed processes can achieve atomic distributed transactions.
   
   
4. Discuss ways that distributed processes can prevent deadlock.
   
   
5. Discuss distributed deadlock detection.
   
   
6. Discuss election algorithms.
   
   

1. Discuss domains, capabilities, access lists, and access matrices.
   
   

1. Discuss authentication procedures.
   
   
2. Discuss threats such as trojan horse, trap door, worm, virus.
   
   
3. Discuss threat monitoring.
   
   

1. Discuss Unix design principles and innovations.
   
   
2. Discuss fork, execve, wait, and vfork.
   
   
3. Discuss CPU scheduling under Unix.
   
   
4. Discuss the 4.2BSD file-system.
   
   
5. Discuss the advantages and disadvantages of writing the majority of an operating system in a high-level language.
   
   

1. No questions yet.
   
   

1. No questions yet.
   
   

1. Describe automatic job sequencing. What important advantage(s) did it bring to computing systems design?
   
   
2. Describe off-line processing. What important advantage(s) did it bring to computing systems design?
   
   
3. Describe spooling. How does it differ from off-line processing?
   
   
4. For each of the following operating systems, name one important innovation it contributed: Atlas, XDS-940, THE, RC 4000, CTSS, MULTICS, OS 360, and Mach.