Unit 2 Flashcards
is a program in execution and
must progress in a sequential fashion.
Process
to select the next task and get it
ready for processing
Dispatch
A program is an __________; only when
a processor “breathes life” into it, does it
become the “active” entity we call a process
inanimate entity
a group of digits, characters or
works that are held in one reaction of an I/O
medium and handled as an input.
Blocks
Input becomes available.
Wake up
TCB
Thread Control Block
if the process does not
voluntarily relinquish the CPU before the
time interval expires, the interrupt causing
the operation system to regain control.
Timerrunout
PCB
process control block
is the module that gives control of the
CPU to the process selected by the short-term
scheduler
Dispatcher
The processes that are residing in the main
memory and are ready and waiting to execute are
kept on a list called the
Ready queue.
its policy is to give all users equal service.
Single Queue Mechanism
its policy is to give high priority on a short processor.
Multiple Queue Mechanism
is also known as task control block. It serves as a dictionary for any information that may vary from process to process.
Process Control Block
is an OS that elects the next job to be
admitted to the system and the next process to run.
Scheduler
It determines when a particular program should be loaded into the memory for each execution.
Long Term (High Level / Job Scheduler)
It determine which I/O device will be used to
service a particular I/O request. It is executed somewhat more frequently than to make swapping decision.
Medium Term (I/O Scheduler)
Select from the process that are ready to execute and allocates the CPU to one of them. A process may execute for only a few milliseconds before waiting for an I/O request.
Short Term (CPU scheduler / Dispatcher)
is the state of indefinite waiting that processes may reach when competing for system resources or when attempting to communicate.
Deadlock
if each resource type has only one instance, only one process at a time can use the resource.
Mutual Exclusion
there must exist a process that is
holding at least one resource and is waiting to
acquire additional resources that are currently being
held by other process
Hold and Wait
a resource can be released only voluntarily by the process holding it after that process has completed its task.
No Preemption
there must exist a set of processes waiting for resources that is held by other processes and so on.
Circular Wait / Cycle
is a useful tool to represent the deadlock situation in a system.
resource allocation graph (RAG)
The state may be new, ready, running, waiting, halted and so on.
Process State
