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38 Cards in this Set

  • Front
  • Back
Three things Operatings Systems do
1.) Execute user programs and make solving userproblems easier2.) Make the computer system convenient to use3.) Use the computer hardware in an efficient manner
Four Components of a computer system
1.) Hardware2.) Operating system3.) Application Programs4.) Users
What is an Interrupt signal
A signal from a device causing the computer system to stop and figure out what to do next
What is a Cache
A temporary storage area storing data that is most likely to be reused
Key Features of an Operating system
1.) multiprogramming 2.) timesharing (multitasking)3.) interrupt driven4.) dual mode
Define multi programming
organizes jobs so that the CPU always has a jobto execute
Define Timesharing (Multitasking
Logical Extension of Multiprogramming where CPU will switch so frequently that users are able to interract with each task while they are running
Define Interrupt driven
starts executung list of computer instruction s in one program and keeps running the instructions until either (A) they can't go any further or (B) an interrupt signal is sensed. After the interrupt signal is sensed, the computer either resumes running the program it was running or begins running another program.
Describe the dual mode
Allows the OS to PROTECT itself along with other components FROM basic mis-uses from users
Within Dual Mode there are 2 modes called?
The User mode and Kernel mode (supervision mode/privilege mode)
Whats the difference between Kernel and User mode

Kernel mode can directly access hardware whereas user mode cannot

What is Mode bit
Provides ability to distinguish if a system is running user code or kernel code. Privileged instructions are only executed in kernel mode and provide protection to the system.
What does a system calll do
It changes the mode to kernel mode
What does returning from a call do
Resets mode to User mode
What are the process life cycle stages
Define Process
is a program in execution/uni of work within the system
Difference between a program and a process
Program = passive entityProcess = active entity
What are the process management activities that the operating system is responsible for
Creating and deleting both user and system processesSuspending and resuming processes Providing mechanisms for process synchronization Providing mechanisms for process communication Providing mechanisms for deadlock handling
What are the 6 OS Functions
- Process Management- Memory Management- Storage Management- I/O Management- Protection- Security
What is Memory Management
Memory management determines what is in memory and when
What are the 3 Memory Management activities
- Keeping track of which parts of memory are currently being used and by whom - Deciding which processes (or parts thereof) and data to move into and out of memory - Allocating and deallocating memory space as needed
What has Paging and Segmentation goto to do with Memory Management
Paging is a logical concept technique for faster access to data WHEREAS Segmentation is one of the most common ways of achieving memory protection
What are the Operation system activities with Mass-Storage Management
Free space managementStorage AllocationDisk Scheduling
Define Protection in terms of OS
any mechanism for controlling access of processes or users to resources defined by the OS
Define Security
defense of the system against internal and external attacks
What is an I/O Subsystem
Abstraction level between the user and the operationsof the hardware with the Operating system
What is an I/O subsystem responsible for
Memory management of I/O including buffering (storing data temporarily while it is being transferred), caching (storing parts of data in faster storage for performance), spooling (the overlapping of output of one job with input of other jobs)
Name 2 I/O methods
Synchronous and Asynchronous
Whats the difference between Synchronousand Asynchronous
Synchronous: 1 at a timeAsynchronous: multiple at a time
What is Synchronous Execution
Wait for process to finish before moving on to another task
What is Asynchronous Execution
Can move on to another task while process is executing
What is Buffering
Storing data temporarily while it is being transferred
What is Spooling
The overlapping of output of one job with input of other jobs
Access control is determined by
User idGroup idPrivilege escalation
Define Privilege escalation
allows user to change to effective ID with more rights
What is User id used for in terms of security

User id is to identify ownership and privileges to access and modification to files and folders

Define Kernel mode

In Kernel mode, the executing code has complete and unrestricted access to the underlying hardware. It can execute any CPU instruction and reference any memory address. Kernel mode is generally reserved for the lowest-level, most trusted functions of the operating system. Crashes in kernel mode are catastrophic; they will halt the entire PC.

Define User mode

In User mode, the executing code has no ability to directly access hardware or reference memory. Code running in user mode must delegate to system APIs to access hardware or memory. Due to the protection afforded by this sort of isolation, crashes in user mode are always recoverable. Most of the code running on your computer will execute in user mode.