Page 99 - DCAP403_Operating System

Operating System

Notes When two or more concurrent processes are reading or writing some shared data and the
final result depends on who runs precisely when, are called race conditions.

Critical Section is a part of the program where the shared memory is accessed. Mutual
Exclusion is a way of making sure that if one process is using a shared modifi able data,
the other processes will be excluded from doing the same thing. Semaphore is a protected
variable whose value can be accessed and altered only by the operations P and V and
initialization operation called ‘Semaphoiinitislize’.
Message passing is a form of inter process communication used in concurrent computing,
where the communication is made by the sending of messages to recipients.

5.9 Keywords

CPU scheduling: It is the basic of multiprogramming where the task of selecting a waiting process
from the ready queue and allocating the CPU to it.
CPU utilization: It is an important criterion in real-time system and multi-programmed systems
where the CPU must be as busy as possible in performing different tasks.
Response Time: The amount of time between a request is Submitted and the first response is

produced is called response time.

Throughput: The number of processes executed in a specified time period is called throughput.
Turnaround Time: The amount of time that is needed to execute a process is called turnaround
time. It is the actual job time plus the waiting time.

Waiting Time: The amount of time the process has waited is called waiting time. It is the
turnaround time minus actual job time.

5.10 Self Assessment

Fill in the blanks:

1. A ......................... header will contain pointers to the first and last PCBs in the list.
2. ......................... scheduling is the basics of multiprogramming.
3. A major task of an operating system is to manage a collection of ......................... .
4. The CPU is ......................... to the selected process by the dispatcher.
5. ......................... is a method of CPU scheduling that is a preemptive version of shortest job
next scheduling.
6. A ......................... scheduling algorithm will simply put the new process at the head of the
ready queue.
7. ......................... scheduling is essentially concerned with memory management.
8. The most common goal of scheduling is to ......................... of a task set.
9. ......................... scheduling involves assigning a task to a particular processor within the
system.
10. ......................... scheduling is really the easiest way of scheduling.

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