1.2.1. Systems Software Flashcards
What is an operating system?
a collection of programs that work together, to provide an interface between the user and computer
What are the functions of an operating system?
- memory management<br></br>2. user interface<br></br>3. utility software<br></br>4. file management<br></br>5.interrupt service routine<br></br>6.I/O management<br></br>7.security
What is a similarity of paging and segmentation?
both are used when RAM space is insufficient, which can cause disk thrashing
What is a difference between paging and segmentation? (2 things)
- paging uses equal sized sections called pages<br></br><br></br>- segmentaiton uses variable sized, logical sections call segments
How is virtual memory used when there is not enough RAM? (3 things)
- a section of the hard drive is used to act as RAM<br></br>2. sections of programs not currently being used are temporarily moved into virtual memory through paging<br></br>3. freeing up memory for other programs in RAM
What is an interrupt?
a signal generated by software or hardware to indicate to the processor that a process needs attention
What is the process of the interrupt service routine? (6 steps)
- interrupt register is checked at the end of each fetch-decode-execute cycle<br></br><br></br>2. if there is an interrupt that exists with a higher priority compared to the current process, the current contents of the registers in the CPU are transferred into a stack<br></br><br></br>3. the relevent interrupt service routine is loaded into RAM<br></br><br></br>4. a flag is set to signal that the ISR has begun and is reset once the ISR has finished<br></br><br></br>5. the interrupt register is checked again, if there are interrupts of a higher priority, the process is repeated<br></br><br></br>6. if there are no interrupts with a high priority, the contents of the stack are popped and placed back into the special memory registers
Which of these scheduling algorithm are pre-emptive or non pre-emptive?<br></br>FCFS, SRT, SJF, MLFQ, RR
pre-emptive - RR, SRT, MLFQ<br></br>non-preemptive - FCFS, SJF
What is an advantage of using multilevel feedback queues for scheduling?
services most urgent interrupts first
What is a disadvantage of using multilevel feedback queues for scheduling?
hard to implement
What is the defenition of a real-time operating system?
real-time operating systems perform a task within a guaranteed time frame
Where are real-time operating systems used?
in systems where a response within a given time frame is critical
What are the 3 functions of the BIOS when running tests upon computer start up?
- POST which ensures all hardware is correctly connected and functional<br></br>2. checks the CPU clock, memory and processor<br></br>3. tests for external memory devices
What is the role of a device driver?
to enable the OS to interact with hardware devices
What are 3 examples where a virtual machine may be used?
- testing programs<br></br>2. protection from malware<br></br>3. running software, compatible with different versions and types of operating systems
What is an advantage of intermediate code?
platform independent
What is an disadvantage of intermediate code?
slower execution
What are 3 examples of where real-time operating systems are used?
- self driving cars<br></br>2. life support sytems<br></br>3. power systems
What does POST stand for?
power on self test
