Flashcards
OS Ch2 Flash Cards
Flashcards do conjunto (25)
- 1List 6 useful things operating systems do for the user, and 3 they do for the systemUser:
1. Providing a user interface
2. Execute Programs
3. Handle I/O operations
4. Manipulate File Systems
5. Communicate with other hosts
6. Error detection and protection
System:
1. Resource Allocation
2. Accounting
3. Protection and Security - 2Describe a Command Line InterpreterCLI is used for direct command entry. This is sometimes implemented in the kernel, and sometimes by systems programs.
There are a number of shells available as CLIs
Mainly just fetches a command from a user and executes it. Some commands are built in, just being the names of programs. - 3Describe a GUIA graphical user interface uses icons, and implements mouse actions.
Many systems contain both CLI and GUI interfaces. - 4What is a system call? How do they work? What is the benefit of APIs?A system call is a programming interface written to services provided by the OS, usually written in C/C++, which allow as to call commands like open(), write(), exit(), running processes, etc.
APIs usually allow us to call system commands in a high level way. That way the programmer doesn't need to know many details of the OS.
The system call *interface* invokes the system call in the OS kernel, returning the status of the system call and any return values: - 5How do we pass parameters in system calls? There are three ways.The simplest way to pass parameters into the OS is through the registers, but there may be more parameters than registers.
Parameters stored in a block or table in memory could also work. This is what linux and solaris does.
Paremters can be pushed onto and popped off the stack by the OS.
The latter two methods don't limit the length of parameters being passed. - 6What are the seven kinds of system programs?1. File Management and Modification
2. Status info (e.g. time, date, disk space, number of users, etc.)
3. Programming language support - compilers, assemblers, debuggers, etc.
4. Program loading and execution
5. Communication: web pages, messaging, file transfer, etc.
6. Background Services, for error logging, disk checking, process scheduling, etc.
7. Application programs (run by users, don't pertain to the system, don't know why it's included in this list!) - 7Tell us about how to design an operating system. Go!Well, there isn't a perfect way to design an OS, it really depends on the goals. Users want something fast, reliable, easy, and safe, where the system goals are about being easy to implement, maintain, error-free, etc..
- 8When designing an OS, what is the difference between a policy and a mechanism?Policy is WHAT we want done, a mechanism is HOW we will get it done.
- 9How is an OS usually implemented?Earlier OSs tended to be in Assembly language, but now done in higher level langauges like C and C++ (actually, usually a mix, with some assembly, a lot of C, and even some python and PERL).
Higher level languages are easier to port to other hardware. - 10What is the layered approach to understanding an OS?With the layered approach, the OS is divided into layers, with layer 0 (core) being the hardware, and N being the user interface.
Practically, it means that layers are selected such that each module uses functions (operations) and services of a lower level only. (okay?...) - 11What is the Microkernel system structure, and what are it's costs and benefits?This is when as much is moved from the kernel to the user space as possible. Communication takes place between user modules using message passing.
The cost is that there is a bit of performance lag because of all the message passing, however it is easier to extend a microkernel, easier to port the OS to new architectures, more reliable (as less code is running in the kernel), and more secure. - 12What is purpose of System Calls?To allow user level processes to request services of the operating system.
- 13What are the 5 major activities of an OS with regard to process management?a. Creating and deleting user and system processes
b. Suspending and resuming processes
c. Providing mechanisms for process synchronization...
d. ... process communication...
e. ... and deadlock handling - 14What are the three major activities of an OS with regard to memory management?a. Keep track of which parts of memory are currently being used and by whom
b. Decide which processes are to be loaded into memory when space becomes available
c. Allocate and deallocate space as needed - 15What are the three major activities of an OS with regard to memory management?- Free space management
- Storage allocation
- Disk scheduling - 16What system calls have to be executed by an CLI or shell in order to start a new processAssuming a Unix system, a fork() call followed by an exec() system call.
- 17What is the purpose of system programs?System programs can be thought of as bundles of useful system calls, providing system-level functionality to users without needed to write their own programs to solve common problems
- 18What are the main advantages and disadvantages of layered system design?As in all cases of modular design, easier to debug due to limitations of where a bug could occur. No disadvantages given by text, but maybe it can come at the cost of efficiency or communication overhead.
- 19Why is there usually a number associated with each system call?So that the system call interface can use a table indexed according to these numbers. Allows fast and easy access.
- 20What kind of systems calls would you consider commands like end, abort, load, execute, wait, malloc, etc.?Process Contol
- 21What kind of systems calls would you consider commands like create, delete, open, write, etc?File Management
- 22What kind of systems calls would you consider commands like request/release device, write/read device, logically attach/detatch devices?Device Management
- 23What kind of systems calls would you consider commands like get/set time, system data, process attributes?Information Maintenance
- 24What kind of systems calls would you consider commands like create/delete communication connection, send/receive, and transfer status info?Communications
- 25What's the difference between a core dump and a crash dump?A CORE DUMP: generated by application failures, dumping files containing memory of the process
A CRASH DUMP: generated by Operating System failure, dumping files containing kernel memory.
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- Operating Systems FlashCards sobre OS Ch2 Flash Cards, criado por Joel Pearson em 13-10-2018.
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- Joel Pearson
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