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What are the two main stages of the instruction cycle?
Fetch and Execute
What does the Program Counter hold?
Address of the next instruction (increments after fetched)
What is the purpose of the Accumulator in instruction execution?
Temporary storage
Where does the Instruction Register store the instruction?
Processor
Can data be transferred interchangeably from processor to memory?
Yes
Can data be transferred interchangeably from processor to IO?
Yes
What type of operations can a data processing processor perform on data?
Arithmetic operations
How can control instructions alter the sequence of instructions?
By changing the sequence of instructions
What do interrupts cause the CPU to do?
Suspend current process to run the interrupt handler process
Where can interrupts come from?
Hardware (e.g. power failure) or software (e.g. segmentation fault)
How are multiple interrupts dealt with?
By either disabling interrupts or prioritizing high priority interrupts
What does the principle of locality refer to in terms of memory access?
Spatial refers to accessing memory locations that are close by, while Temporal refers to the likelihood of accessing a memory location again after it has been accessed
What is Direct Memory Access (DMA)?
When the CPU tells a device directly where to put data in memory without involving the CPU in the transfer process
What is an advantage of using DMA for slow devices?
It is more efficient as the device puts data in memory when done, allowing the CPU to focus on other tasks
Why is DMA considered more efficient for slow devices?
It eliminates the need for the CPU to repeatedly check the device for data transfer status
What is Direct Memory Access (DMA)?
DMA is when the CPU tells a device directly where to put data in memory once it is completed, without involving the CPU in the process.
What is the advantage of DMA?
DMA is significantly more efficient for slow devices as it allows the device to put data in memory when it is done, freeing the CPU for other tasks.
What are the responsibilities of OS in storage management?
1. Process Isolation 2. Automatic allocation and Management 3. Supporting Modular Programming 4. Protection and Access Control 5. Storage for long term
Monolithic vs Microkernel
Monolithic: Everything runs under one executable, runs in Kernel mode, less context switching, easier to develop, simpler system. Microkernel: Highly modular, high fault tolerance, more overhead due to interprocess communication, more context switching.
Context switching
Switching between user and kernel mode.
Fault Tolerance
Ability to proceed with system when failures occur.
Modular
Customizability.
SIGINT
Signal Interrupt. Terminate process and clean up resources. Eg. kill -INT PID or kill -2 PID. CTRL+C in Linux Terminal.
SIGKILL
Signal Kill. Force stop a process immediately with no clean up. Eg. You shut down your pc and Windows notifies that you have processes still running and you click Shut down anyways. kill -9 PID or kill -KILL PID.
SIGSTOP
Signal Stop. Pause a process. Eg. kill -STOP PID or kill -19 PID. CTRL+Z in Linux Terminal.
SIGCONT
Signal Continue. Continue a previously paused signal. Eg. kill -CONT PID or kill -18 PID.
kill -L
Gives a list of Signals. Eg. to find a specific one: kill -L | grep SIGSTOP
What does the Linux command 'kill -CONT PID' do?
Continue a previously paused signal for the specified process ID.
What signal number is used to continue a paused process in Linux?
18
How can you list all available signals in Linux using the 'kill' command?
kill -l
