ENVS 1800 Lecture 11: ENVS 1800 Lecture 11 Notes
14 May 2018
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ENVS 1800 Lecture 11 Notes – More Quota
Introduction
• In the latter case, most well designed programs will suspend themselves, unless the
interruption is expected to be extremely brief.
• This state transition is known as blocking, and the process remains in a blocked state
until its I/O requirement is complete.
• When the I/O operation is complete, the operating system moves the process from the
blocked state back to the ready state.
• This state transition is frequently called wake-up.
• Blocking can also occur when a process is waiting for some event other than I/O to occur
• For example, a completion signal or a data result from another process.
• No preemptive systems will allow a running process to continue running until it is
completed or blocked.
• Preemptive systems will limit the time that the program remains in the running state to
a fixed length of time corresponding to one or more quanta.
• If the process remains in the running state when its time limit has occurred, the
operating system will return the process to the ready state to wait further time for
processing.
• The transition from the running state to the ready state is known as time-out.
• When the process completes execution, control returns to the operating system, and
the process is destroyed or killed or terminated.
• Some operating systems provide one or more additional states, which are used to
improve the efficiency of the computer system.
• Some processes make heavy demands on particular resources, say, a disk drive or a
printer
• Even the CPU, in such a way that other processes are unable to complete their work in
an efficient manner
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