SLR4- Operating Systems and System Software Flashcards
What is multitasking?
When you have more then one program open and running at the same time.
How does the processor handle multitasking?
It allocates a small amount of time to each process and cycles between them. This happens so quickly it appears as if multiple programs are executing simultaneously.
How is data stored?
In files.
What does the extension of the filename do?
Tells the operating system which program to load into.
What does user management do?
- Allows multiple users to log into the same computer.
- The operating system will retain settings for each user, such as icons, desktop backgrounds etc.
- Each user may have different access rights to files and programs.
What does a scheduler manage?
- Which process to execute next.
- The length of time the next process can execute for.
What is first come first serve?
- Works like a supermarket queue.
- Processes are executed in the order that they arrive.
- If a process takes a long time, the others simply have to wait.
What is shortest job first?
- Picks the processes that take the shortest amount of time and runs them until they finish.
- Scheduler needs to know how long each process will take.
What does the operating system do?
Provides an interface between the user and the hardware.
How does the user interact with the hardware?
- Through application software.
- The operating system provides a platform for the operating system to run.
How does the user interact with the application software?
Through a user interface, which allows for a friendly and familiar interaction.
What is the purpose of utility programs?
Maintenance, examples include:
- Encryption software
- Compression software
- De-fragmentation software.
What are the main roles of the operating system?
- Application Software
- User interface
- Memory/resource management
- Hardware
- Utility programs
- Device drivers
- File management.
- Handing interrupts.
What is the purpose of device drivers?
Translate operating system instructions into instructions that can be understood by the hardware.
What is round robin?
- Each process is allocated a fixed amount of time, known as a time slice or quantum.
- If the process is not complete by the end of its time slice, it returns to the back of the ready queue.
What is shortest time remaining?
- Similar to shortest job first.
- A pre-emptive algorithm, meaning processes can be suspended if a higher priority process joins the queue.
How does Multi-level feedback queues (MLFQ) work?
- Different queues can have different priorities.
- Scheduler can move jobs between different queues as needed.
What are pages?
- Physical divisions in RAM
- Fixed size
- Made to fit sections of memory
- Programs are split up into a given number of pages
- Takes no account of how it splits the program, only that it splits it into fixed-sized pages.
What are segments?
- Logical divisions
- Different sizes
- Complete sections of programs
List 3 similarities between paging and segmentation.
- Both allow programs to run despite insufficient memory.
- Both pages and segments are stored on disk.
- Both pages and segments are transferred into memory when needed.
List 3 differences between paging and segmentation.
- Pages are fixed size, whereas segments are different sizes.
- Pages are made to fit sections of memory, segments are complete sections of programs.
- Pages are physical divisions, segments are logical divisions.
What is an interrupt?
A way for devices and applications to signal to the processor that they require attention.
What is the interrupt service routine?
- A program with a set of instructions that need to be fetched, decoded and executed to carry out the operations of the interrupt.
- This means that the program counter needs to be changed to the address for the first instruction of the interrupt.
When an interrupt is received, what happens to the values held in registers?
- Values are copied into the stack.
- Pushed onto the stack in a stack frame, effectively saving them for later retrieval.
