Topic 2 - Operating System
What are the 3 components of a process?
- An executable program - Associated data needed by the program - Execution context of the program • All information the operating system needs to manage the process
What is one of the key characteristics (modern operating system)
- Assigns only a few essential functions to the kernel • Address spaces • Interprocess communication (IPC) • Basic scheduling
Explain the accounting service in an OS
- Collect usage statistics - Monitor performance - Used to anticipate future enhancements - Used for billing purposes
What is the Executive
- Contains base operating system services • Memory management • Process and thread management • Security • I/O • Interprocess communication
Describe a thread
- Dispatchable unit of work - executes sequentially and is interruptable
What does Distributed operating systems do?
- Provides the illusion of a single main memory space and single secondary memory space
Describe Symmetric Multiprocessing
- There are multiple processors - These processors share same main memory and I/O facilities - All processors can perform the same functions
What is Multiprogramming
When one job needs to wait for I/O, the processor can switch to the other job
Monitor executes in...?
system mode - Kernel mode - Privileged instructions are executed - Protected areas of memory may be accessed
User program executes in...?
user mode - Certain instructions may not be executed
Define a process
• A program in execution • An instance of a program running on a computer • The entity that can be assigned to and executed on a processor • A unit of activity characterized by a single sequential thread of execution, a current state, and an associated set of system resources
What are some definitions of an operating system
• A program that controls the execution of application programs • An interface between applications and hardware • Exploits the hardware resources of one or more processors • Provides a set of services to system users • Manages secondary memory and I/O devices
What is the purpose of paging
• Allows process to be comprised of a number of fixed-size blocks, called pages • Virtual address is a page number and an offset within the page • Each page may be located anywhere in main memory • Real address or physical address in main memory
Whats the purpose of virtual memory
• Allows programmers to address memory from a logical point of view • No hiatus between the execution of successive processes while one process was written out to secondary store and the successor process was read in
What are the 4 principles of information protection and security?
• Availability - Concerned with protecting the system against interruption • Confidentiality - Assuring that users cannot read data for which access is unauthorized • Data integrity - Protection of data from unauthorized modification • Authenticity - Concerned with the proper verification of the identity of users and the validity of messages or data
What are the 3 main objective of an operating system?
• Convenience - Makes the computer more convenient to use • Efficiency - Allows computer system resources to be used in an efficient manner • Ability to evolve - Permit effective development, testing, and introduction of new system functions without interfering with service
What are the Kernel-Mode Components?
• Executive • Kernel • Hardware abstraction layer (HAL) • Device drivers • Windowing and graphics systems
What are the 3 principles of scheduling and resource management?
• Fairness - Give equal and fair access to resources • Differential responsiveness - Discriminate among different classes of jobs • Efficiency - Maximize throughput, minimize response time, and accommodate as many uses as possible
How would you define UNIX?
• Hardware is surrounded by the operating system software • Operating system is called the system kernel • Comes with a number of user services and interfaces - Shell - Components of the C compiler
What is the purpose of file systems
• Implements long-term store • Information stored in named objects called files
What are some difficulties with designing system software?
• Improper synchronization - Ensure a process waiting for an I/O device receives the signal • Failed mutual exclusion • Nondeterminate program operation - Program should only depend on input to it, not on the activities of other programs • Deadlocks
What are some of the features of hardware which contribute to the running of a computer?
• Memory protection - Do not allow the memory area containing the monitor to be altered • Timer - Prevents a job from monopolizing the system • Privileged instructions - Certain machine level instructions can only be executed by the monitor • Interrupts - Early computer models did not have this capability
Describe the characteristics of a Modern operating system
• Microkernel architecture • Multithreading • Symmetric multiprocessing (SMP) • Distributed operating systems • Object-oriented design
Describe the Windows Architecture
• Modular structure for flexibility • Executes on a variety of hardware platforms • Supports application written for other operating system
What is the kernel?
• Portion of operating system that is in main memory • Contains most frequently used functions • Also called the nucleus
What are some principles of memory management
• Process isolation • Automatic allocation and management • Support of modular programming • Protection and access control • Long-term storage
What are the rolls of system management?
• Process isolation • Automatic allocation and management • Support of modular programming • Protection and access control • Long-term storage
What is UniProgramming
• Processor must wait for I/O instruction to complete before preceding
What are some services provided by the operating system?
• Program development - Editors and debuggers • Program execution • Access to I/O devices • Controlled access to files • System access • Error detection and response • Accounting
what is the operating system responsible for?
• Responsible for managing resources • Functions same way as ordinary computer software - It is program that is executed • Operating system frequently relinquishes control of the processor and must rely on the processor to allow it to regain control of the processor
what are some points how time sharing works
• Using multiprogramming to handle multiple interactive jobs • Processor's time is shared among multiple users • Multiple users simultaneously access the system through terminals
Describe the characteristics of system structure
• View the system as a series of levels • Each level performs a related subset of functions • Each level relies on the next lower level to perform more primitive functions • This decomposes a problem into a number of more manageable subproblems
What does the Device drivers do?
- Translate user I/O function calls into specific hardware device I/O requests
Why use Object-oriented design?
- Used for adding modular extensions to a small kernel - Enables programmers to customize an operating system without disrupting system integrity
Explain the points of Error detection and response
- Internal and external hardware errors • Memory error • Device failure - Software errors • Arithmetic overflow • Access forbidden memory locations - Operating system cannot grant request of application
Describe Hardware abstraction layer (HAL)
- Isolates the operating system from platformspecific hardware differences
So what are some of the characteristics of Simple Batch Systems
- Monitors • Software that controls the sequence of events • Batch jobs together • Program branches back to monitor when finished
So what are some of the characteristics of Serial Processing (older way how computers work)
- No operating system - Machines run from a console with display lights, toggle switches, input device, and printer - Schedule time - Setup included loading the compiler, source program, saving compiled program, and loading and linking
What is a Modified microkernel architecture
- Not a pure microkernel - Many system functions outside of the microkernel run in kernel mode
What are the characteristics of Multithreading (modern operating system)
- Process is divided into threads that can run concurrently • Thread • Process is a collection of one or more threads
