02 01 Operating System Services P1 — Transcript

Full transcript

1. 0:08[Music]
2. 0:25hi there
3. 0:26this video lecture covers operating
4. 0:29system services
5. 0:33so this will be the outline of the
6. 0:34discussion
7. 0:35okay so we will be talking about the
8. 0:37operating system services
9. 0:39the user and operating system interface
10. 0:42system calls
11. 0:44system services linkers and loaders
12. 0:47why applications are operating systems
13. 0:50specific
14. 0:51design and implementation
15. 0:53operating system structure
16. 0:55building and booting an operating system
17. 0:58and operating system debugging
18. 1:01okay so this video covers a lot of
19. 1:04technical things and technical matters
20. 1:06so bear with me
21. 1:08all right
22. 1:09so for the objective of this video
23. 1:13so at the end of this video you should
24. 1:14be able to identify services provided by
25. 1:16an operating systems
26. 1:18illustrate how system calls are used to
27. 1:22provide operating system
28. 1:24services compare and contrast monolithic
29. 1:28layered microkernel
30. 1:30modular and hybrid strategies for
31. 1:32designing operating systems
32. 1:35illustrator process for booting and
33. 1:38operating system
34. 1:40apply tools for monitoring operating
35. 1:42system performance
36. 1:44and design and implement kernel modules
37. 1:46for interacting with a linux kernel
38. 1:50so let's start
39. 1:53so operating system services so this
40. 1:56pertains to the functionalities of
41. 1:58operating systems provided to the users
42. 2:02all right
43. 2:03so an operating system provides an
44. 2:05environment for execution
45. 2:07of programs and services
46. 2:09to programs and users
47. 2:12so
48. 2:13imagine your computer without an
49. 2:15operating system how can we run a
50. 2:17program how can we execute a program
51. 2:20or how can we interact with
52. 2:22the hardware okay so those are just some
53. 2:25of the operating system services
54. 2:27okay
55. 2:28so
56. 2:29one set of operating system services
57. 2:32provides a function that are helpful to
58. 2:34the user so this includes user interface
59. 2:36or ui
60. 2:38okay
61. 2:38now in terms of the user interface the
62. 2:41old computers are using this command
63. 2:44line all right or the cli the command
64. 2:47line
65. 2:48interface so i use the term ci or
66. 2:51command interface or command line
67. 2:54interface or cli interchangeably on the
68. 2:56discussion
69. 2:57so some operating systems are using gui
70. 3:00so we are well aware about it okay so
71. 3:03most of the operating systems are using
72. 3:05gui
73. 3:06for the mobile devices so they are using
74. 3:09gui and at the same time touch screen
75. 3:11okay you also have batch
76. 3:13all right
77. 3:14so aside from user interface another
78. 3:16service provided by the operating system
79. 3:19is of course
80. 3:21program execution the operating systems
81. 3:24allows us to execute programs
82. 3:27okay
83. 3:28next is io operations okay so a running
84. 3:32program may require an i o like what we
85. 3:34discussed in chapter one
86. 3:36which may involve a file or an i o
87. 3:39device
88. 3:41okay so mostly or most of the time
89. 3:44this peripherals connected to the
90. 3:46computer
91. 3:47are sending an io if needed okay
92. 3:51for the
93. 3:54uh temporary hold
94. 3:56okay or stop of these services or the
95. 3:59execution of the operating systems to
96. 4:01give way
97. 4:02to the request of the i o
98. 4:05okay
99. 4:06so next is file system manipulation
100. 4:10so the system file is of particular
101. 4:12interest so program needs to read and
102. 4:14write files and directories create and
103. 4:17delete them search them
104. 4:19list file information
105. 4:22and permission management so with file
106. 4:24system manipulations we users are
107. 4:26allowed by the operating systems to
108. 4:29create
109. 4:30to edit delete
110. 4:32okay organize folders
111. 4:34so those are one of the services
112. 4:36provided by the operating systems
113. 4:40okay
114. 4:42next so aside from those also the
115. 4:45operating systems allows us to
116. 4:47communicate okay communicate with the
117. 4:50hardware communicate with the other
118. 4:52computers on the network communicate
119. 4:54over the internet okay
120. 4:57so next is error detection
121. 4:59so os needs to be constantly aware of
122. 5:02the possible errors
123. 5:04so there are a lot of errors okay so in
124. 5:07the operations
125. 5:08okay and the operating system provides
126. 5:11services for such
127. 5:13so it may occur in the cpu and memory
128. 5:15hardware
129. 5:16in io devices
130. 5:18or in user program itself
131. 5:21all right
132. 5:22so for each type of error
133. 5:25os should take the appropriate action to
134. 5:28ensure correct and consistent or
135. 5:30consistent computing
136. 5:32so debugging facilities can greatly
137. 5:34enhance the users and programmers
138. 5:36abilities to efficiently use the system
139. 5:42okay so aside from those services
140. 5:45okay
141. 5:46basically another set of os functions
142. 5:49exist for ensuring the efficient
143. 5:50operation of the system itself via
144. 5:53resource sharing
145. 5:54okay
146. 5:55so
147. 5:56this includes resource allocation
148. 5:59lagging protection and security
149. 6:02okay so for the resource allocation
150. 6:04basically one of the function of the
151. 6:06operating system is to allocate
152. 6:08resources
153. 6:09to every process requesting it
154. 6:11so every time we open a program
155. 6:13basically
156. 6:14that program
157. 6:16okay
158. 6:17once you run it it becomes a process and
159. 6:20a process for it to run and execute
160. 6:23needs resources like memory
161. 6:25as a cycle or a time of the cpu and
162. 6:28other resources needed
163. 6:30okay resource allocation
164. 6:32next is lagging
165. 6:34so to keep track of which users and how
166. 6:36much
167. 6:38and what kind of computer resources
168. 6:41are being
169. 6:42used
170. 6:43or being are currently being held better
171. 6:45users
172. 6:47so protection and security
173. 6:49so the owners of information stored in a
174. 6:51multi-user or network computer systems
175. 6:54may want to control the use of that
176. 6:56information
177. 6:57concurrent processes should not
178. 7:00interfere with each other so protection
179. 7:03it involves ensuring that all access to
180. 7:05the system
181. 7:06is controlled
182. 7:08okay whereas security
183. 7:11of the system from outsiders requires
184. 7:13user authentication so authentication
185. 7:17means we are asked to log in we are
186. 7:20asked to use our own username and
187. 7:22password to get inside the operating
188. 7:25system okay so that is security that is
189. 7:28one of the service provided by the
190. 7:30operating systems
191. 7:32all right
192. 7:35now
193. 7:36for
194. 7:38the resource allocation okay so let me
195. 7:40open my task manager here
196. 7:42okay so when you say resource allocation
197. 7:45basically we can monitor the resource
198. 7:47allocation of the operating systems on
199. 7:49our computer or on our device okay
200. 7:53so if you if you will observe in here
201. 7:56okay
202. 7:57my cpu utilization is 42
203. 8:01okay so and i am running 168 processors
204. 8:03here
205. 8:05all right
206. 8:06so
207. 8:07168 processors with 1900 plus threads
208. 8:12okay
209. 8:13so the memory being used is 61
210. 8:16and so on so basically
211. 8:19these resources
212. 8:21is shown here okay so i have here the
213. 8:24running applications or the programs
214. 8:26okay
215. 8:27and then we have here the resources
216. 8:29allocated by the operating systems
217. 8:32all right so basically the operating
218. 8:35systems is a resource allocator
219. 8:39okay
220. 8:42next
221. 8:43a view of an operating system services
222. 8:47okay
223. 8:48so
224. 8:50from the first chapter or chapter one we
225. 8:52have shown the interactivity
226. 8:55okay or the components of the computer
227. 8:58systems
228. 8:59which includes hardware
229. 9:01all right operating systems
230. 9:04okay the services
231. 9:06all right are the application programs
232. 9:10and the user
233. 9:11and other system programs
234. 9:14okay
235. 9:15so
236. 9:16we cannot directly communicate with the
237. 9:18hardware basically we are using the
238. 9:20application programs here
239. 9:22okay so to interact with operating
240. 9:24systems so that operating systems will
241. 9:26relay that to the hardware
242. 9:29all right
243. 9:30so on the application programs here it
244. 9:32could be in the form of a graphical user
245. 9:34interface all right or a touch screen or
246. 9:37a command line
247. 9:38so basically we can interact with the
248. 9:41operating systems either by tapping the
249. 9:43command on the cli okay
250. 9:45by touching an icon on the screen touch
251. 9:49screen or maybe
252. 9:51we are using this a mouse okay
253. 9:53interactive or interactivity with the
254. 9:56graphical user interface
255. 9:58okay
256. 9:59and all of this
257. 10:01we communicate with operating systems
258. 10:04via system calls
259. 10:06all right so it's just that we have to
260. 10:08call or we have to make a system call so
261. 10:11that we can interact with the services
262. 10:13and functionalities provided by the
263. 10:15operating systems and this services
264. 10:17includes program execution
265. 10:20io operations file systems
266. 10:22communications resource allocation
267. 10:25accounting
268. 10:26error detection and protection and
269. 10:28security
270. 10:29so this summarizes
271. 10:31the services provided by the operating
272. 10:34systems to the users
273. 10:36all right
274. 10:39next so let's take the command line
275. 10:42interpreter or the ci or command
276. 10:45interpreter okay
277. 10:47so the ci or the command line
278. 10:49interpreter gets
279. 10:51and process the next user request and
280. 10:54launches the requested programs
281. 10:56so in some systems
282. 10:58the ci or the cli may be incorporated
283. 11:01directly into the kernel
284. 11:03okay
285. 11:04so more
286. 11:06commonly the ci is a separate program
287. 11:10that launches
288. 11:12once the user logs in or otherwise
289. 11:14accesses the system
290. 11:18okay
291. 11:19so in
292. 11:21linux or in unix
293. 11:23this cli
294. 11:24is implemented in many players and they
295. 11:27called it shells okay so in windows
296. 11:31they are using the
297. 11:32command prompt okay so let me open my
298. 11:35cmd here
299. 11:37okay command prompt this is a cli
300. 11:41okay this is how it looked like
301. 11:43this is a command prompt
302. 11:44and also a newer version of windows has
303. 11:48what you call shell
304. 11:49okay or powershell
305. 11:51so if in unix or in linux we have what's
306. 11:54called shell okay born shell corn shell
307. 11:58in windows we also have this power shell
308. 12:01okay
309. 12:02and basically this power cl uses aliases
310. 12:06all right
311. 12:07so for example there are some commands
312. 12:09that still works on
313. 12:12on powershell that was adapted from this
314. 12:15command prompt example so we want to
315. 12:17show the
316. 12:18the
317. 12:19content
318. 12:21of the drive c users id
319. 12:24so these are the contents or these are
320. 12:26the files within it
321. 12:28all right
322. 12:29so this command is also working on the
323. 12:32powershell
324. 12:34okay
325. 12:35so you'll have that
326. 12:36but we have a command adapted from linux
327. 12:40that works here
328. 12:41on powershell okay and this is the
329. 12:45command like list
330. 12:47ls
331. 12:48okay same thing but ls or list is not
332. 12:52working
333. 12:53in command prompt
334. 12:56all right so these are the two command
335. 12:58prompt or sorry command line interpreter
336. 13:01provided by windows so it's either we
337. 13:02use the command prompt or
338. 13:04the windows powershell all right
339. 13:09so this is how
340. 13:11a born shell command interpreter looked
341. 13:13like okay
342. 13:15so similar to that of a dos
343. 13:17but
344. 13:18it's actually a shell
345. 13:20okay
346. 13:21so
347. 13:22the windows power shell was patterned
348. 13:24after this because the old operating
349. 13:27systems from microsoft
350. 13:29doesn't have any shell so it started i
351. 13:31guess in windows 8.
352. 13:34all right
353. 13:35so next is the gui so basically the the
354. 13:39graphics that we saw
355. 13:41on our computer every time we
356. 13:43boot it up okay so that is
357. 13:47a gui
358. 13:48or a graphical user interface so we have
359. 13:50this user-friendly desktop metaphor
360. 13:53interface with an icons okay
361. 13:56and a mouse or
362. 13:59a keyboard
363. 14:01and the monitor
364. 14:02okay so basically this mouse
365. 14:06fyi
366. 14:07okay she did you know that mouse was
367. 14:09invented by xerox corporation
368. 14:12and xerox corporation is basically into
369. 14:15a photocopier business
370. 14:17all right so but then it has found an
371. 14:20application okay it's very useful in a
372. 14:24personal computer and even a laptop
373. 14:25nowadays
374. 14:28okay
375. 14:30next is touchscreen so most of the
376. 14:32smartphones nowadays are using this
377. 14:35touchscreen interfaces okay
378. 14:37so because mice and keyboards are
379. 14:39impractical for small mobile devices so
380. 14:42this normally use a touch screen
381. 14:44interface
382. 14:45just like this um an ios interface here
383. 14:49okay that responds to various patterns
384. 14:52of swipes
385. 14:53or gestures
386. 14:55so when this first came out
387. 14:57they often had a physical keyboard
388. 15:00and or a trackball of some kind
389. 15:02okay built in
390. 15:04but today a virtual keyboard is more
391. 15:06commonly implemented on the touchscreen
392. 15:09all right and it could also be a voice
393. 15:12activated
394. 15:14okay or voice commands
395. 15:16all right
396. 15:20next this is the gui interface of a mac
397. 15:23os all right
398. 15:28so mac has traditionally provided only
399. 15:31the google interface
400. 15:33so with the advent of os x
401. 15:36okay so based partially on unix a
402. 15:38command interface has also become
403. 15:40available so it's just like another form
404. 15:43of operating system just like windows
405. 15:54[Music]
406. 16:02you