Session 2 Flashcards
OS is a _______ _______ and a _______ _______
OS is a control program and a resource allocator
OS Controls execution of _______ to prevent errors and _______ use of the _______
Controls execution of programs to prevent errors and improper use of the computer.
OS Manages all _______
Decides between conflicting _______ for _______ and fair _______ use
OS Manages all resources
Decides between conflicting requests for efficient and fair resource use
Defining OS
A special piece of software that Abstracts and Arbitrates the use of a computer system.
OS Elements
__________
Process, File, Thread, Socket, Memory Page.
OS Elements
Abstraction
Process, File, Thread, Socket, Memory Page.
OS Elements
__________ –How to do it??
Create, schedule, open, write, allocate.
OS Elements
Mechanism –How to do it??
Create, schedule, open, write, allocate.
OS Elements
__________ –What will be done??
Least Recently User, Earliest Deadline First
OS Elements
Policies –What will be done??
Least Recently User, Earliest Deadline First
Operating System Structure
__________
Only one or two levels of code.
Operating System Structure
Simple
Only one or two levels of code.
Operating System Structure
__________
Independent Layers.
Operating System Structure
Layered
Independent Layers.
Operating System Structure
__________
OS built from many user level processes.
Operating System Structure
Microkernel
OS built from many user level processes.
Operating System Structure
__________
Core kernel with dynamically loadable modules.
Operating System Structure
Modular
Core kernel with dynamically loadable modules.
Operating-System Operations
_____ _____- Interrupt ,trap or System call
Question???
When you are at home dozing your chair, how do you know when someone wants to talk to you on the phone?
A)Periodically pick up the phone to see if someone called. - _____
B) Or do you wait till the phone rings to answer it? - _____
Operating-System Operations
Event driven - Interrupt ,trap or System call
Question???
When you are at home dozing your chair, how do you know when someone wants to talk to you on the phone?
A)Periodically pick up the phone to see if someone called. - polling
B) Or do you wait till the phone rings to answer it? - interrupt
Interrupt
_____ sends a special _____ to CPU when _____arrives.
Interrupt
Device sends a special signal to CPU when data arrives.
Interrupt
Responds to _____ _____signal by _____ current _____.
Interrupt
Responds to hardware interrupt signal by interrupting current process.
System Call
A system call is invoked in a variety of ways, depending on the _______ provided by the underlying _______. It is the method used by a _______to request _______by the operating system.
System Call
A system call is invoked in a variety of ways, depending on the functionality provided by the underlying processor. It is the method used by a process to request action by the operating system.
System Call
Instruction which causes the _______ to change _______ .
System Call
Instruction which causes the processor to change mode .
Timer Interrupt
How to prevent Infinite loop ???
Sets interrupts on specific periods (fixed timer) Uses Counters (variable timer)
Timer Interrupt
How to prevent Process Hogging???
Before turning over control to the user, the operating system ensures that the timer is set to interrupt.
Process Management
A process is a _______ in _______ . It is a unit of _______ within the system.
Process Management
A process is a program in execution. It is a unit of work within the system.
Process Management
Program is a _______ entity, process is an _______ entity.
Process Management
Program is a passive entity, process is an active entity.
Process Management
A process needs certain _______—
- including CPU time, memory, files, and I/O devices—to accomplish its _______.
Process Management
A process needs certain resources—
including CPU time, memory, files, and I/O devices—to accomplish its task.
Process Management
Multi-threaded Process – Each _______ has its own _______ Counter.
Process Management
Multi-threaded Process – Each thread has its own Program Counter.
Process Management
Single-threaded process – one _______ counter
Process Management
Single-threaded process – one Program counter
Process Management Activities
Scheduling _______ and _______ on the CPUs .
Creating and deleting both user and system _______.
_______ and resuming processes.
Providing mechanisms for process _______.
Providing _______ for process communication.
Process Management Activities
Scheduling processes and threads on the CPUs .
Creating and deleting both user and system processes.
Suspending and resuming processes.
Providing mechanisms for process synchronization.
Providing mechanisms for process communication.
Memory Management
All _______ in _______ before and after processing
All _______ in _______ in order to execute
Memory management determines what is in _______ when Optimizing CPU utilization and computer response to _______
Memory management activities: Keeping track of which parts of _______ are _______ being used and by _______
Deciding which _______ (or a part of) and _______ to move into and out of _______
_______ and _______ memory space as needed
Memory Management
All data in memory before and after processing
All instructions in memory in order to execute
Memory management determines what is in memory when
Optimizing CPU utilization and computer response to users
Memory management activities
Keeping track of which parts of memory are currently being used and by whom
Deciding which processes (or a part of) and data to move into and out of memory
Allocating and deallocating memory space as needed
Storage Management
OS provides uniform, logical view of information storage
_______ physical properties to logical storage unit - file
Each medium is controlled by device (i.e., disk drive, tape drive)
Varying properties include access speed, capacity, data-transfer rate, access method (sequential or random)
Storage Management
OS provides uniform, logical view of information storage
Abstracts physical properties to logical storage unit - file
Each medium is controlled by device (i.e., disk drive, tape drive)
Varying properties include access speed, capacity, data-transfer rate, access method (sequential or random)
Storage Management
File-System _______
Files usually organized into directories
Access _______ on most systems to determine who can access what
OS activities include
Creating and deleting files and directories
Primitives to manipulate files and dirs
Mapping files onto secondary storage
Backup files onto stable (non-volatile) storage media
Storage Management
File-System management
Files usually organized into directories
Access control on most systems to determine who can access what
OS activities include
Creating and deleting files and directories
Primitives to manipulate files and dirs
Mapping files onto secondary storage
Backup files onto stable (non-volatile) storage media
Mass-Storage Management
Usually disks used to store data that does not fit in _______ _______ or _______ that must be kept for a “long” period of time.
Proper _______ is of central importance
Entire speed of computer operation hinges on disk _______ and its _______
OS activities
Free-space management
Storage allocation
Disk scheduling
Some storage need not be fast
Tertiary storage includes optical storage, magnetic tape
Varies between WORM (write-once, read-many-times) and RW (read-write)
Mass-Storage Management
Usually disks used to store data that does not fit in main memory or data that must be kept for a “long” period of time.
Proper management is of central importance
Entire speed of computer operation hinges on disk subsystem and its algorithms
OS activities
Free-space management
Storage allocation
Disk scheduling
Some storage need not be fast
Tertiary storage includes optical storage, magnetic tape
Varies between WORM (write-once, read-many-times) and RW (read-write)
I/O Subsystem
One purpose of OS is to hide peculiarities of _______ devices from the _______
I/O subsystem responsible for
- _______ _______ of I/O including _______(storing data temporarily while it is being transferred), _______(storing parts of data in faster storage for performance), _______ (the overlapping of output of one job with input of other jobs)
- General device-driver interface
- Drivers for specific hardware devices
I/O Subsystem
One purpose of OS is to hide peculiarities of hardware devices from the user
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)
General device-driver interface
Drivers for specific hardware devices
Protection – any _______ for controlling _______of _______ or users to _______ defined by the OS
Protection – any mechanism for controlling access of processes or users to resources defined by the OS
Protection –
any mechanism for controlling access of processes or users to resources defined by the OS
Security – _______ of the system against internal and external attacks
Huge range, including denial-of-service, viruses, identity theft, theft of service.
Security – defense of the system against internal and external attacks
Huge range, including denial-of-service, viruses, identity theft, theft of service.
Security –
Security – defense of the system against internal and external attacks
Huge range, including denial-of-service, viruses, identity theft, theft of service.
Systems generally first distinguish among users, to determine who can do what
User identities (_______ , security IDs) include name and associated number, one per user
User ID then associated with all files, processes of that user to determine access control
Group identifier (_______ ) allows set of users to be defined and controls managed, then also associated with each process, file
_______ _______ allows user to change to effective ID with more rights
Systems generally first distinguish among users, to determine who can do what
User identities (user IDs, security IDs) include name and associated number, one per user
User ID then associated with all files, processes of that user to determine access control
Group identifier (group ID) allows set of users to be defined and controls managed, then also associated with each process, file
Privilege escalation allows user to change to effective ID with more rights
