Systems Software Flashcards
What is an operating system?
A collection of programs that work together to provide an interface between the user and the computer.
Give 3 functions of an operating system
- Memory management
- Resource management
- I/ O management
- Interrupt management
- Security
- User Interface
- Utility software
What are the similarities and differences between paging and segmentation?
Both: are used when RAM space is insufficient, can cause disk thrashing
P: uses equal-sized sections called pages
S: uses variable-sized, logical sections called segments
Describe how virtual memory is used when there is not enough RAM
A section of the hard drive is used to act as RAM
Sections of programs not currently being used are temporarily moved into virtual memory through paging
This frees up memory for other programs in RAM
What is an interrupt?
A signal generated by hardware or software to indicate to the processor that a process needs attention
Explain the stages of the Interrupt Service Routine
- Interrupt register checked at end of each FDE cycle
- If there’s an interrupt existing with a higher priority to a current priority, the current contents in CPU transferred into stack
- The relevant ISR is loaded into RAM and flag reset once ISR finished
- Interrupt register checked again. If interrupts are of a higher priority, process repeated
- If there are none, contents of stack are popped and place back into the special memory registers
- FDE cycles renews as before
Are these scheduling algorithms pre-emptive or non pre-emptive? FCSF, SRT, SJF, MLFQ, RR
Pre-emptive: RR, SRT, MLFQ
Non pre-emptive: FCSF, SJF
What are the advantages and disadvantages of using Multilevel Feedback Queues for scheduling?
A: services most interrupts first
D: hard to implement
Define a real-time operating system and when it may be used
Real- time OS perform a task within a guaranteed time frame. They are used in systems where a response within a given time frame is critical
Describe three functions of BIOS
- POST (power on self test) which ensures that all hardware is connected correctly and functional
- Checking the CPU clock, memory and processor
- Testing for external memory devices
What is the role of a device driver?
Enables OS to interact with hardware devices
Describe an instance in which virtual memory is used
- Testing programs
- Protection from malware
- Running software compatible with different versions and types of OS
Give one advantage and disadvantage of intermediate code
A: platform independent, portable
D: slower execution
