01 04 OS Operations — Transcript

Full transcript

1. 0:08[Music]
2. 0:21operating system operations
3. 0:24so you've got a bootstrap program simple
4. 0:26code to initialize the system
5. 0:29and then load the kernel
6. 0:31okay
7. 0:32so basically when you boot up your
8. 0:34computer system
9. 0:36so it will start with a bootstrap
10. 0:38program
11. 0:39okay and then it will load the kernel
12. 0:43then afterwards
13. 0:44it will start system demons
14. 0:47system demons are services provided
15. 0:50outside of the kernel
16. 0:52okay
17. 0:53and then you also have the kernel
18. 0:54interrupt driven hardware and software
19. 0:57so hardware ended up
20. 0:58by one of the devices
21. 1:00software interrupt exception or trap
22. 1:03so something like software error so
23. 1:05division by zero is an error that's an
24. 1:07interrupt
25. 1:09request for operating system service or
26. 1:11system call that is also a form of
27. 1:14software interrupt
28. 1:16other processes problems includes
29. 1:18infinite loop
30. 1:20processes modifying other or each other
31. 1:23or the operating system all of those are
32. 1:25software interrupt
33. 1:27okay if the interrupt is caused by a
34. 1:30program we call it
35. 1:31software interrupt
36. 1:33if the interrupt is
37. 1:35caused by a hardware or an io we call it
38. 1:38hardware interrupt
39. 1:43multi-programming or bots system
40. 1:46okay so what are the os features needed
41. 1:49for multi-programming
42. 1:51so first there should be an io routine
43. 1:54supplied by the system
44. 1:56so there should also be memory
45. 1:58management
46. 1:59the system must allocate the memory to
47. 2:02several jobs
48. 2:03when you say job
49. 2:05this is also known as the process
50. 2:08okay or the program and execution
51. 2:12so next would be cpu scheduling or
52. 2:15also known as job scheduling
53. 2:17so the system must choose among several
54. 2:20jobs ready to run
55. 2:22then afterwards
56. 2:23allocation of devices
57. 2:26okay
58. 2:27so in multi-programming single users
59. 2:30cannot always keep cpu and io devices pc
60. 2:34so multi-programming organizes jobs
61. 2:38code and data so cpu always has
62. 2:41one to execute
63. 2:42so in cpu scheduling okay so we have to
64. 2:46keep the cpu as busy as possible
65. 2:49okay so a subset of the total jobs in
66. 2:52the system is kept in the memory
67. 2:55memory is one of the resource
68. 2:57and when you execute a program
69. 3:00we call it job and job needs a resource
70. 3:03like a memory
71. 3:05so one job selected and run via cpu
72. 3:08scheduling or
73. 3:10job scheduling also known as process
74. 3:12scheduling
75. 3:13so when the job has to wait
76. 3:16okay
77. 3:17for i o maybe for example i o switches
78. 3:20to another job
79. 3:22okay so depending on the algorithm being
80. 3:24used so we will be talking about
81. 3:26cpu scheduling on the next
82. 3:29modules
83. 3:33multitasking or the time sharing
84. 3:36so time sharing systems are interactive
85. 3:38computing
86. 3:39so the cpu is multiplexed among several
87. 3:43jobs that are kept in memory
88. 3:45and on disk the cpu is allocated to
89. 3:49a job only if the job is in the memory
90. 3:52okay so a job swapped in and out of the
91. 3:55memory to the desk
92. 3:57so online communication between the user
93. 4:00and the system is provided
94. 4:02so when the operating system finishes
95. 4:04the execution of the command
96. 4:06or of one command
97. 4:08it seeks the next control statement from
98. 4:11the user's
99. 4:13okay
100. 4:14and then online system
101. 4:16must be available for users to access
102. 4:19data encode
103. 4:21now multitasking is a logical extension
104. 4:25of batch systems
105. 4:26the cpu switches jobs so frequently that
106. 4:30the users can interact with each job
107. 4:32while it is running
108. 4:34creating an interactive computing
109. 4:37okay so response time should be less
110. 4:40than one second each user has at least
111. 4:44one program executing in the memory we
112. 4:46call it process so again process is
113. 4:49equivalent to job
114. 4:50okay or
115. 4:52a program in execution
116. 4:55so if several jobs are ready to run at
117. 4:57the same time
118. 4:58we have to impose cpu scheduling
119. 5:01and under cpu scheduling we have
120. 5:03different algorithms like
121. 5:05first come first serve
122. 5:07short job first preemptive and
123. 5:09unpreemptive
124. 5:10priority preemptive and non-preemptive
125. 5:13you also brown robin
126. 5:15you could have the combinations of
127. 5:18different algorithms
128. 5:19multi-level cueing and you also have the
129. 5:22multi-level feedback okay
130. 5:24now if processes don't fit in memory
131. 5:28then we are going to execute or impose
132. 5:30swapping
133. 5:32swapping moves them in and out to run
134. 5:37and virtual memory allows the execution
135. 5:40of processes
136. 5:41not completely in the memory
137. 5:46so we have here a memory layout for a
138. 5:49multi-programmed system
139. 5:51several jobs are kept in the main memory
140. 5:53at the same time
141. 5:54and cpu is multiplexed among them
142. 6:00dual mode operation
143. 6:02so sharing system resources requires
144. 6:05operating system
145. 6:07to ensure that an incorrect program
146. 6:09cannot cause other programs to execute
147. 6:11incorrectly
148. 6:13okay so provide hardware support
149. 6:16to differentiate between at least two
150. 6:19modes of operation
151. 6:21so you've got the user mode
152. 6:23okay
153. 6:24and you've got the monitor mode also
154. 6:27known as
155. 6:28the kernel mode
156. 6:29okay or system mode
157. 6:32now when you say user mode
158. 6:35execution done on behalf of the user
159. 6:39when you say kernel mode
160. 6:41execution is done on behalf of the
161. 6:43operating system
162. 6:45okay
163. 6:46so it has what you called mode bit
164. 6:48provided by hardware
165. 6:50so it provides ability to distinguish
166. 6:53when system is running user code or
167. 6:56kernel code
168. 6:57when a user is running
169. 6:59a mode bit is
170. 7:01user
171. 7:03when the kernel code is executing the
172. 7:04mode bit is kernel
173. 7:07okay
174. 7:08so how do we guarantee that user does
175. 7:10not explicitly set
176. 7:12the mode bit into kernel
177. 7:14so system call changes mode to kernel
178. 7:17return from call resets it to the user
179. 7:19mode
180. 7:20so some instructions designated as
181. 7:23privileged only executable in kernel
182. 7:26mode
183. 7:29now how about transition from user to
184. 7:32kernel mode
185. 7:33okay
186. 7:34so as mentioned earlier there are two
187. 7:36modes of operation in the operating
188. 7:38system to make sure it works correctly
189. 7:41so this are the user mode
190. 7:44okay
191. 7:46and the kernel mode
192. 7:49now
193. 7:50let's talk about user mode
194. 7:52or user processes
195. 7:53the system is in the user mode when the
196. 7:56operating system is running a user
197. 7:58application
198. 7:59such as handling a text editor
199. 8:03so the transition from user mode to
200. 8:05kernel mode occurs
201. 8:07when the application requests the help
202. 8:09of the operating system or an interrupt
203. 8:13or a system call occurs
204. 8:16like what we have here so system car
205. 8:18system call occurs
206. 8:20then that will shift to kernel mode
207. 8:24okay
208. 8:24so the mode bit is set to one in the
209. 8:28user mode
210. 8:29it is changed from one to zero when
211. 8:31switching from
212. 8:32user mode to the kernel mode
213. 8:37now let's talk about kernel mode
214. 8:40the system starts internal mode when it
215. 8:43boots
216. 8:44and after the operating system is loaded
217. 8:47it executes the application in user mode
218. 8:51there are some privileged instructions
219. 8:53that can only be executed internal mode
220. 8:57these are interrupt instructions
221. 9:00okay
222. 9:01input output management etc so if the
223. 9:04privileged instructions are executed in
224. 9:06the user mode it is illegal and a trap
225. 9:10is
226. 9:11generated
227. 9:13all right
228. 9:14so the mode bit
229. 9:16is set to zero
230. 9:18in the kernel mode
231. 9:20okay
232. 9:21and then it is changed from zero to one
233. 9:24when switching from kernel mode to the
234. 9:27user mode
235. 9:31timer so your operating system also uses
236. 9:34timers
237. 9:35it's a timer to prevent infinite loop or
238. 9:38process
239. 9:39hugging resources
240. 9:41so timer is set to interrupt the
241. 9:43computer after some time period
242. 9:46so keep a counter that is decremented by
243. 9:49the physical clock
244. 9:51so operating system set the counter
245. 9:54in privileged instruction
246. 9:55when counter 0 generates an interrupt
247. 9:58set up before scheduling process to
248. 10:00regain control
249. 10:02or terminate program that exists the
250. 10:04allotted time
251. 10:09your operating system also is capable of
252. 10:11doing management okay so one of that is
253. 10:15process management
254. 10:17so the operating system is responsible
255. 10:19for the following activities in
256. 10:21connection with process management
257. 10:24okay
258. 10:25so
259. 10:27a process is a program in execution as
260. 10:30defined earlier this is similar to jobs
261. 10:33so
262. 10:34this video presentation or this video
263. 10:37lecture uses process
264. 10:40jobs interchangeably and all of this
265. 10:42pertains to a running program or a
266. 10:45program in execution
267. 10:47so it is a unit of work within the
268. 10:49system
269. 10:50program is passive entity
270. 10:53process is an active entity
271. 10:56okay so when the program is not running
272. 10:58that's a passive
273. 11:00when a program runs it becomes a process
274. 11:03or it creates a process and that is
275. 11:05known as the active entity
276. 11:07okay
277. 11:09so process needs resources to accomplish
278. 11:12its tasks
279. 11:13so whenever you run an application it
280. 11:15needs a cpu time
281. 11:17it needs memory it needs io it needs
282. 11:20files
283. 11:21and it requires initialization of data
284. 11:25so process termination requires reclaim
285. 11:28of any reusable resources
286. 11:31so basically
287. 11:32process management includes process
288. 11:34creation and deletion
289. 11:37okay
290. 11:38so process termination requires reclaim
291. 11:41of any reusable resources
292. 11:44so process suspension and resumption is
293. 11:46also part
294. 11:47okay so next would be a single threaded
295. 11:51process has one program counter
296. 11:53specifying location of the next
297. 11:55instruction to execute
298. 11:58so processes executes instructions
299. 12:01sequentially one at a time
300. 12:03until completion
301. 12:06so multi-threaded processes has one
302. 12:08program counter per thread
303. 12:10so typically system has many processes
304. 12:14some user some operating system running
305. 12:16concurrently
306. 12:18on one or more cpus
307. 12:20concurrency by multiplexing the cpus
308. 12:23among the processes threats
309. 12:27so in process management
310. 12:29there is what's called provision of
311. 12:31mechanisms for process synchronization
312. 12:34and process communication
313. 12:40now what are the activities on process
314. 12:42management
315. 12:44the operating system is responsible for
316. 12:46the following activities in connection
317. 12:48with process management
318. 12:49so creating and deleting both user and
319. 12:52system processes
320. 12:54suspending and resuming processes
321. 12:57providing mechanism for process
322. 12:59synchronization
323. 13:01providing mechanisms for process
324. 13:03communication
325. 13:05and providing mechanisms for deadlock
326. 13:08handling
327. 13:09okay so basically we can see the
328. 13:12processes or the number of processes
329. 13:14in our computer
330. 13:16when we
331. 13:18get into
332. 13:19the task manager
333. 13:21okay
334. 13:23so let me open the task manager
335. 13:26here we go
336. 13:28okay
337. 13:29so
338. 13:30performance
339. 13:32basically i'm running 200 for processors
340. 13:35right now
341. 13:36okay there are
342. 13:382 161 threads
343. 13:41all right so cp utilization the speed is
344. 13:45there
345. 13:45the memory utilization
346. 13:48okay the disk utilization wi-fi
347. 13:52gpu and so on
348. 13:53so these are being provided by the
349. 13:55operating systems
350. 13:57okay
351. 13:58so my virtualization is enabled and i am
352. 14:01using or this computer is using three
353. 14:04caches so l1 l2 and l3 cache
354. 14:07all right
355. 14:08so all of these activities
356. 14:11okay can be monitored
357. 14:12via task manager
358. 14:15okay you can even see the applications
359. 14:17running
360. 14:18okay you've got the background and the
361. 14:20foreground processes here
362. 14:22okay
363. 14:23so all of this
364. 14:24are being performed by the operating
365. 14:26system
366. 14:30management
367. 14:32memory is a large array of words or
368. 14:35bytes
369. 14:36it's with its own address
370. 14:39so it is a repository of quickly
371. 14:41accessible data shared by the cpu and i
372. 14:45o devices
373. 14:47okay the main memory is volatile as we
374. 14:50described earlier on
375. 14:52okay so it is a volatile storage device
376. 14:55it loses its content in case of system
377. 14:59failure
378. 15:00so the operating system is responsible
379. 15:02for the following activities
380. 15:04in connection with the memory management
381. 15:08so first
382. 15:09keep track of which parts of the memory
383. 15:12are currently being used and by whom
384. 15:15okay so going back to our
385. 15:19task manager here okay so we can see
386. 15:22applications
387. 15:24consuming
388. 15:26the resources the memory the test or the
389. 15:29cpu and the network there
390. 15:32okay
391. 15:33next would be
392. 15:35deciding which process or parts thereof
393. 15:38and data to move into and out of the
394. 15:40memory
395. 15:42okay so which means decide which process
396. 15:45to load when the memory space becomes
397. 15:48available
398. 15:50and last would be allocating and the
399. 15:52allocating memory spaces
400. 15:54as needed
401. 15:59next would be file system management
402. 16:02so let's start with the definition of
403. 16:04file
404. 16:05okay
405. 16:06so file is a collection of related
406. 16:09information defined by each creator
407. 16:12so commonly
408. 16:14files represent programs
409. 16:17both source and object forms and data
410. 16:21the operating system is responsible for
411. 16:23the following activities
412. 16:25in connection with the file management
413. 16:28okay
414. 16:29so one would be
415. 16:31file creation and deletion
416. 16:33so creating and deleting files and
417. 16:36directories
418. 16:38you've got directory creation and
419. 16:40deletion also
420. 16:41bringing tips to manipulate files and
421. 16:43directories
422. 16:45support of primitives
423. 16:48for manipulating files and directories
424. 16:51okay so mapping files into secondary
425. 16:54storage
426. 16:56and
427. 16:58file backup unstable or non-volatile
428. 17:01storage
429. 17:02media okay now the operating system
430. 17:05provides a uniform logical view of
431. 17:08information storage
432. 17:11so abstract physical properties the
433. 17:13logical unit
434. 17:15that's a file
435. 17:17okay now each medium is controlled by a
436. 17:20device
437. 17:21desk drives state drives etc
438. 17:24so varying properties include speed
439. 17:27okay capacity
440. 17:30transfer rate and the access method
441. 17:33would it be sequential on some storage
442. 17:35devices like tape
443. 17:37or random access
444. 17:44random memory
445. 17:47okay or the mass storage management
446. 17:49so since the main memory
447. 17:52or the primary storage is volatile
448. 17:54and
449. 17:55too small to accommodate
450. 17:57all data and programs permanently so the
451. 18:00computer system must provide a secondary
452. 18:03storage
453. 18:04okay that is the backup the main memory
454. 18:08most modern computer systems uses desks
455. 18:11as the principle of online storage
456. 18:14medium
457. 18:16for both programs and data
458. 18:19now the operating system is responsible
459. 18:21for the following activities in
460. 18:22connection with desk management
461. 18:25you've got the free space management in
462. 18:27mounting and unmounting
463. 18:30the storage allocation
464. 18:32disk scheduling or the cpu scheduling or
465. 18:34process scheduling
466. 18:36partitioning and protection
467. 18:39so usually
468. 18:40disks used to store data and does not
469. 18:43fit in domain memory
470. 18:45or data must be kept for a long period
471. 18:47of time on the master edge
472. 18:50so proper management
473. 18:52is
474. 18:53required okay
475. 18:55and
476. 18:56that is essential importance
477. 18:58so the utmost importance
478. 19:00would be imposed on the mass storage
479. 19:02management
480. 19:04so the entire speed of computer
481. 19:06orientation hinges on this subsystem
482. 19:09and its algorithms
483. 19:11caching
484. 19:13important principle performed at many
485. 19:16levels in computer
486. 19:18in hardware operating system and
487. 19:19software level
488. 19:21so information in use copied from slower
489. 19:24the faster storage temporarily
490. 19:27checking use of high-speed memory
491. 19:30to hold recently accessed data
492. 19:34so it requires a cash management policy
493. 19:38okay
494. 19:39so
495. 19:39faster storage or cash check first to
496. 19:42determine if information is there
497. 19:45if it is there information used directly
498. 19:48from the cash
499. 19:49if not
500. 19:50data copied to cache and use there
501. 19:53caching introduces another level in
502. 19:56storage hierarchy
503. 19:58this requires data that is
504. 20:00simultaneously stored
505. 20:02in more than one level to be consistent
506. 20:08so cash smaller than the storage being
507. 20:10cashed
508. 20:11cash management important design problem
509. 20:15and cash size and replacement
510. 20:18policy characteristics of various types
511. 20:21of
512. 20:23storage
513. 20:25so movement between levels of storage
514. 20:27hierarchy can be explicit or implicit
515. 20:30okay so from the diagram that we are
516. 20:32presented earlier starting at the bottom
517. 20:36okay so the capacity going upward going
518. 20:38to the register
519. 20:40is decreasing
520. 20:42but the speed
521. 20:44from the bottom
522. 20:45or from the magnetic tape going to the
523. 20:48register
524. 20:49you've got faster
525. 20:51okay faster access as we move upward
526. 20:54okay
527. 20:55now typical size
528. 20:57for register is less than 1 kb
529. 21:00okay and if you will observe for
530. 21:02magnetic disk it's less than 10
531. 21:04terabytes
532. 21:06the size increases or the capacity
533. 21:08increases
534. 21:09okay
535. 21:10now implementation technology
536. 21:13for registers custom memory with
537. 21:14multiple ports cmos
538. 21:17gas is on chip or off chip cmos usually
539. 21:21it is within
540. 21:22the cpu
541. 21:24main memory is in cmos sram
542. 21:28mounted on the motherboard biomodules
543. 21:31the solid state uses the flash memory
544. 21:34and the magnetic discard the hard disk
545. 21:35uses magnetic disk
546. 21:39okay
547. 21:40so you also have other factors like
548. 21:42access time bandwidth
549. 21:45managed by okay so registers are managed
550. 21:48by the compilers
551. 21:50cache hardware main memory is being
552. 21:52managed by the operating system
553. 21:56okay
554. 21:56so with the solid state device and the
555. 21:59magnetic
556. 22:00hard disk
557. 22:02okay so backed up
558. 22:06you've got cache main memory
559. 22:08desk
560. 22:09okay and then discord
561. 22:14how about migration of data
562. 22:17let's say data a from
563. 22:19disk to register
564. 22:21okay so assuming that
565. 22:24our programmer is stored in hard disk
566. 22:27so first it will be migrated to the main
567. 22:29memory
568. 22:30afterward it will be moved
569. 22:33to the cpu memory or cache and then to
570. 22:36the hardware registers
571. 22:38so multitasking environment must be
572. 22:41careful to use most recent value
573. 22:44no matter where it is stored in the
574. 22:47storage hierarchy
575. 22:49so multi-processor environment must
576. 22:51provide cost coherency
577. 22:53in hardware such that all cpus have the
578. 22:56most recent value in their cache
579. 23:00so distributed environment situation
580. 23:03even more complex
581. 23:05several copies of data can exist
582. 23:09okay
583. 23:10and we will be covering
584. 23:13various or different solutions okay so
585. 23:16as we progresses with our
586. 23:18course
587. 23:20io subsystem
588. 23:22one purpose of the operating system is
589. 23:24to hide peculiarities of hardware
590. 23:26devices from the user
591. 23:29io subsystem is responsible for memory
592. 23:31management
593. 23:33okay general device driver interface and
594. 23:36drivers for specific hardware devices
595. 23:40so on the memory management of io
596. 23:43including buffering
597. 23:45storing data temporarily while it is
598. 23:47being transferred
599. 23:49that's buffering
600. 23:50caching
601. 23:51storing parts of data in faster storage
602. 23:55for performance
603. 23:56you also have spooling
604. 23:58the overlapping of output of one job
605. 24:02with input of the other jobs
606. 24:04okay
607. 24:05so memory management includes buffering
608. 24:08caching and spooling
609. 24:13protection and security
610. 24:15so protection refers to a mechanism
611. 24:18for controlling access by programs
612. 24:22processes
613. 24:23or users
614. 24:24to both system and user resources
615. 24:28okay
616. 24:29so the protection mechanism must
617. 24:32distinguish
618. 24:34between authorized and unauthorized
619. 24:36usage
620. 24:37okay
621. 24:39so there should be user identities user
622. 24:41ids or security ids
623. 24:44includes name and associated number one
624. 24:47per user
625. 24:48okay
626. 24:50so the id then associate with all files
627. 24:53processes of that user
628. 24:56to determine access control
629. 24:59so there is also group identifier or
630. 25:01group id
631. 25:02allow set of users to be defined and
632. 25:05controls
633. 25:06managed
634. 25:08then also associated with each process
635. 25:10file
636. 25:12privilege escalation allows users to
637. 25:14change the effective id
638. 25:16with more rights
639. 25:18okay so providing
640. 25:20means of enforcement
641. 25:23all right
642. 25:24so when you say security
643. 25:26defense of the system against internal
644. 25:28or external attacks
645. 25:30so huge range including the dial of
646. 25:32service worms viruses
647. 25:35identity theft depth of service
648. 25:38okay and this are part of the
649. 25:42computer security or network security
650. 25:47virtualization
651. 25:49so allows operating system to run
652. 25:51applications within other oss
653. 25:54fast growing okay industry
654. 25:58sometimes you are using emulation
655. 26:00software used when source cpu type
656. 26:03different from the target type
657. 26:05okay so generally slowest method
658. 26:08when computer language not compiled to
659. 26:10native code
660. 26:12we need an interpretation or interpreter
661. 26:15so virtualization os natively compiled
662. 26:18for cpu
663. 26:20running guest oss also natively compiled
664. 26:24so consider a vmware running windows xp
665. 26:26guests
666. 26:28each running application
667. 26:30all on the native windows xp host os
668. 26:34so also it requires a virtual machine
669. 26:37manager which provides virtualization
670. 26:39services
671. 26:41so usually we are creating virtual
672. 26:43machines
673. 26:44okay so the virtual machine takes the
674. 26:47layered approach to its logical
675. 26:49conclusion
676. 26:50it threats hardware
677. 26:52and the operating systems kernel as
678. 26:54though they were all hardware
679. 26:57okay so a virtual machine provides an
680. 27:00interface identical to underlying bare
681. 27:03hardware
682. 27:04the operating system creates the
683. 27:06illusion
684. 27:08of multiple processes
685. 27:10each executing on its own processor
686. 27:13with its own virtual or memory
687. 27:20okay so use cases involve laptops and
688. 27:23desktops running multiple oss for
689. 27:25exploration or compatibility
690. 27:29so apple laptop running mac os
691. 27:31host
692. 27:33windows as guest okay developing apps
693. 27:36for multiple oss without having multiple
694. 27:38systems
695. 27:39so quality assurance testing
696. 27:41applications without having multiple
697. 27:43systems
698. 27:44and executing and managing compute
699. 27:46environments within data centers
700. 27:49so these are just some of the advantages
701. 27:52of virtual machines
702. 27:55okay so vmm can run natively in each
703. 27:58case or in which case they are also the
704. 28:00host there is no general purpose host
705. 28:05okay so vmware esx and citrix send
706. 28:08server
707. 28:09okay
708. 28:10one of the disadvantage of
709. 28:12virtualization is that if you have
710. 28:15minimal resources
711. 28:17okay so that's the problem because all
712. 28:19the resources on your computer
713. 28:22are shared
714. 28:25computing environments and
715. 28:26virtualization
716. 28:28okay so in here
717. 28:30you have a single hardware kernel and
718. 28:32then processes
719. 28:33okay so this is a typical setup of a
720. 28:36computer system
721. 28:38now let us be here there are some
722. 28:41implementations of virtual machines okay
723. 28:44the hardware are shared among different
724. 28:47virtual mac virtual machines
725. 28:49each virtual machine
726. 28:51has their own kernel
727. 28:53and
728. 28:55its virtual machine is running different
729. 28:57processes
730. 28:58all of those
731. 29:00running on top of a single hardware
732. 29:03okay
733. 29:04so there is just a virtual machine
734. 29:07manager
735. 29:08which manages the hardware
736. 29:14distributed systems
737. 29:17so a distributed system is a collection
738. 29:20of
739. 29:21processors that do not share memory or a
740. 29:24clap
741. 29:25each processor has its own local memory
742. 29:28another term for distributed system is a
743. 29:31network or a lan
744. 29:33wide area network
745. 29:34metropolitan area network or the
746. 29:36personal area network so all of this
747. 29:39pertains to
748. 29:40distributed system
749. 29:42the processor in the system are
750. 29:44connected through a communication
751. 29:46network
752. 29:47okay so communication takes place using
753. 29:50a protocol
754. 29:52like tcp
755. 29:55a distributed system provides user
756. 29:57access to various system resources
757. 30:01access to shared resources
758. 30:04allows computation speed up
759. 30:06increased data availability
760. 30:09and enhanced reliability
761. 30:12distribute the computation among several
762. 30:14physical processors
763. 30:17you've got something like a loosely
764. 30:18coupled system where in each processor
765. 30:21has its own local memory
766. 30:23processor communicates with one another
767. 30:26through various communication lines such
768. 30:29as the high speed buses or telephone
769. 30:31lines
770. 30:32so there are advantages
771. 30:35and disadvantages of distributed systems
772. 30:38advantages includes
773. 30:40resource sharing
774. 30:42computation speed up
775. 30:44or load sharing reliability and
776. 30:46communication
777. 30:48this basically requires
778. 30:51a networking infrastructure
779. 30:53okay so something like local area
780. 30:55networks wide area networks
781. 30:57may either client server or peer-to-peer
782. 31:00systems
783. 31:02all right
784. 31:11[Music]
785. 31:19you