02 03 Operating System Services P3 — Transcript

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1. 0:08[Music]
2. 0:23okay
3. 0:24so next why applications are operating
4. 0:27systems specific
5. 0:28okay
6. 0:30now on this slide what is said here is
7. 0:32that once you have created a program in
8. 0:35windows it should be running only on
9. 0:37windows
10. 0:38all right so once you have created a
11. 0:41program in mac os okay it should be
12. 0:44running on mac os
13. 0:45okay so apps compiled on one system
14. 0:48usually
15. 0:50not executable on the other operating
16. 0:51systems
17. 0:53so each operating system provides its
18. 0:55own unique system calls
19. 0:57okay so
20. 0:58from the previous slides okay we have
21. 1:01shown some of the
22. 1:04or the difference the differences
23. 1:06between the windows and the unix system
24. 1:09calls
25. 1:10okay so when we created a code for
26. 1:13windows of course
27. 1:14you cannot run that for unix because the
28. 1:16system calls that you used in windows is
29. 1:19for windows only
30. 1:21okay so apps can be multi-operating
31. 1:24systems so written in interpreted
32. 1:26language like python ruby
33. 1:28all right and interpreter available on
34. 1:31multiple operating systems so that's the
35. 1:33time
36. 1:34we could have an application or an apps
37. 1:38that is running in different platforms
38. 1:40okay so i've written a language that
39. 1:42includes a vm containing the running app
40. 1:45like java okay
41. 1:47so java can run in any platform right
42. 1:50so use standard language like c
43. 1:52compile separately on the operating
44. 1:54system to run on it
45. 1:56okay
46. 1:57so we have what's called an application
47. 1:59binary interface or abi
48. 2:02this is an architecture equivalent of
49. 2:04api so defines how different components
50. 2:07of binary code
51. 2:09can interface for a given operating
52. 2:12systems
53. 2:13on a given architecture cpu et cetera
54. 2:17all right
55. 2:20okay next is design and implementation
56. 2:25okay
57. 2:26so design goals basically requirements
58. 2:30define properties
59. 2:32which the finance system must have
60. 2:34and are necessary first step in
61. 2:36designing any large complex systems
62. 2:39okay so there is what you call
63. 2:43a user requirement
64. 2:45okay
65. 2:46so user requirements are features that
66. 2:48users care
67. 2:50about and understand and are written in
68. 2:52commonly understood vernacular
69. 2:56so they generally do not include any
70. 2:58implementation details
71. 3:00and are written similar to the product
72. 3:02descriptions so one might find a sales
73. 3:06brochure or outside the shrink wrap box
74. 3:10okay that's user requirements okay
75. 3:13that's very important
76. 3:15next is system requirements or system
77. 3:17goals there okay
78. 3:19so system goals
79. 3:22these are written for developers
80. 3:25and include more details about
81. 3:27implementation specifics
82. 3:29performance requirements
83. 3:31compatibility constraints standard
84. 3:33compliance etc
85. 3:35so this requirements
86. 3:37serve as a contract between the customer
87. 3:40and the developer
88. 3:41okay and
89. 3:43between developers and subcontractors
90. 3:45maybe okay and it can get quite detailed
91. 3:50all right so you'll have designing
92. 3:52implementations
93. 3:53okay so user goals and system goals or
94. 3:57in some text book they use user
95. 3:59requirements
96. 4:01and system requirements
97. 4:03okay
98. 4:05so requirements for operating systems
99. 4:08can vary greatly depending on the
100. 4:10planned scope and usage of the system so
101. 4:12single user multi-user
102. 4:15specialized system general purpose
103. 4:18high or low security performance needs
104. 4:21operating systems environment etc
105. 4:24all right
106. 4:27next how about the mechanisms and
107. 4:29policies here
108. 4:31okay so policies or policy determine
109. 4:34what is to be done
110. 4:36well mechanism all right
111. 4:38mechanism determine how is it to be
112. 4:41implemented
113. 4:43okay
114. 4:44so if properly separated and implemented
115. 4:47policy changes can be easily adjusted
116. 4:50without rewriting the code
117. 4:53so by just adjusting parameters or
118. 4:56possibly loading new data on
119. 4:57configuration files
120. 4:59all right so for example
121. 5:01the relative priority of background
122. 5:04versus the foreground tasks
123. 5:06okay when you say background this are
124. 5:08the applications running
125. 5:10okay
126. 5:11without
127. 5:13without the users
128. 5:16getting or without the users noticing it
129. 5:20all right so these are the applications
130. 5:21running at the background
131. 5:23or this is usually associated with
132. 5:25operating systems
133. 5:26right
134. 5:29okay so next is implementation
135. 5:32so traditionally
136. 5:34all right
137. 5:35oss were written in assembly language
138. 5:39so this provides direct control
139. 5:42over hardware related issues but
140. 5:45an explicit or intricably
141. 5:48inextricably tied
142. 5:51a particular os to a particular hardware
143. 5:53platform
144. 5:55okay
145. 5:56so recent advances in compiler
146. 5:59efficiencies mean
147. 6:00that most modern oss are written in c
148. 6:05and more recently c plus plus
149. 6:08all right so c our c plus plus is not
150. 6:11obsolete yet okay
151. 6:13so in the industry these are mostly used
152. 6:16on the
153. 6:18background programming okay or back-end
154. 6:21programming
155. 6:22all right
156. 6:24so critical sections of code are still
157. 6:26written in assembly language
158. 6:28or in c compiled to assembly
159. 6:31and then fine-tuned and optimized
160. 6:34by
161. 6:35hand from there
162. 6:37okay
163. 6:37so operating systems may be developed
164. 6:39using emulators
165. 6:42of the target hardware particularly if
166. 6:44the real hardware isn't available
167. 6:46or not built yet right so we are using
168. 6:49this emulation software
169. 6:51okay
170. 6:52so or not suitable platforms for
171. 6:54development examples smartphones game
172. 6:56consoles and other similar devices
173. 7:00okay the emulation
174. 7:02or the emulator emulator as they call it
175. 7:04can allow an os to run on a non-native
176. 7:07hardware
177. 7:10all right
178. 7:20[Music]
179. 7:28you