Lecture 5 Flashcards
What does a multiprogrammed OS signify?
That the OS can accommodate multiple programs being loaded into Main Memory
What is throughput?
The number of jobs that can be completed in a unit of time
What is mean response time?
The average time after which a process gives an output
What are context switches?
The time taken to check, change or move to another process
What is a Gantt Chart used for?
To visually represent the order in which processes are executed by the CPU
WHat is turn around time (TAT)
Total amount of time spent by a process inside the computer Finish time – Arrival time = TAT
Is the OS a process?
Yes
What are the two main elements of a process
Program code and context data.
What is a process control block (PCB)?
A data structure to store information about processes
What are the 8 main attributes of the PCB?
Process ID, State, Priority, PC, Context Data, Memory Pointers, I/O status info, Accounting info,
What does the Process ID PCB attribute hold?
A unique identifier for the process
What does the State PCB attribute hold?
What the process is doing (Running on CPU or not)
What does the Priority PCB attribute hold?
An assigned priority for the process
What does the Program Counter (PC) PCB attribute hold?
The address of the next instruction of this process
What does the Context Data PCB attribute hold?
Data Previously calculated or data the process is working on.
What does the memory pointers PCB attribute hold?
References to memory locations used by the process
What does the I/O status Information PCB attribute hold?
What I/O the process uses and what the I/O does/is doing
What does the Accounting information PCB attribute hold?
General information about the process. BUS time, arrival time, size
What are some of the reasons for process creation?
-opening an application
-system level services (created by kernel)
-system log in =init= forks background processes
-parent creates child process “forks”
What are some of the reasons for terminating a process?
- Closing an application
- System log out
- Errors
- Normal completion
- Starvation
- Parent kills child
- Main memory unavailable
- I/O failure
- Time overrun
