Page 74 - DCAP403_Operating System

Unit 4: Process Management

Processes are often called tasks in embedded operating systems. Process is the entity to Notes
which processors are assigned. The rapid switching back and forth of CPU among processes
is called multi-programming.
A thread is a single sequence stream within in a process. A process can have five states like

created, ready, running, blocked and terminated.
A process control block or PCB is a data structure (a table) that holds information about a
process.
Time-Run-Out occurs when the scheduler decides that the running process has run long
enough and it is time to let another process have CPU time.
Dispatch occurs when all other processes have had their share and it is time for the fi rst
process to run again. Wakeup occurs when the external event for which a process was
waiting (such as arrival of input) happens. Admitted occurs when the process is created.
Exit occurs when the process has fi nished execution.

4.15 Keywords

Admitted: It is a process state transition which occurs when the process is created.
Blocking: It is a process state transition which occurs when process discovers that it cannot
continue.
Dispatch: It is a process state transition which occurs when all other processes have had their
share and it is time for the first process to run again.

Exit: It is a process state transition which occurs when the process has fi nished execution.
Multiprogramming: The rapid switching back and forth of CPU among processes is called
multiprogramming.

Process control block (PCB): It is a data structure (a table) that holds information about a
process.
Process management: It is an operating system’s way of dealing with running multiple processes
at once.
Process: It is the entity to which processors are assigned.
Thread: A thread is a single sequence stream within in a process.
Time-Run-Out: It is a process state transition which occurs when the scheduler decides that the
running process has run long enough and it is time to let another process have CPU time.
Wakeup: It is a process state transition which occurs when the external event for which a process
was waiting (such as arrival of input) happens.

4.16 Self Assessment

Fill in the blanks:
1. Interrupt driven processes will normally run at a very ........................ priority.
2. Processes are often called ........................ in embedded operating systems.

3. The term “process” was first used by the designers of the ........................ in ........................ .
4. In new state, the process awaits admission to the ........................ state.
5. The operating system groups all information that it needs about a particular process into a
data structure called a process descriptor or ........................ .

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