Notetaking for Operating Systems (Fall 2018) - Revision history

R.samanfar: /* Course Notes */

2018-09-12T17:58:03Z

Course Notes

← Older revision		Revision as of 17:58, 12 September 2018
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	If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.		If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.
	~~== Course Notes ==~~
	~~=== Lecture-1 ===~~
	~~====Introduction====~~
	~~'''why is an operating system important?'''~~
	*Only certain programs run on certain operating systems
	*Customization
	*Interface
	~~We program at different levels of abstraction~~
	*Abstraction - make system easy to use, divide program into smaller understandable
	~~pieces~~
	*most portable - the web
	**works on almost all operating systems
	*the web browser is an operating system (eg: chromebook)
	~~'''How do programs run at the same time?'''~~
	*Originally, one program used to control the whole system, now for example there are
	~~around 270 threads running at once on a laptop~~
	*A program executes instructions → '''the processor fetches an instruction from
	~~memory, decodes it and executes it'''~~
	*Similar to a political system: Authoritarian dictatorship
	*Virtualizing the CPU: illusion that a single CPU has a large number of smaller virtual
	~~CPUs.~~
	*Policy: to determine which program runs first
	~~'''Operating systems'''~~
	*body of software to determine which programs to run, allow programs to share memory,
	~~enabling programs to interact with devices~~
	*the OS takes a physical resource (such as the processor, or memory, or a disk) and
	~~transforms it into a more general, powerful, and easy-to-use virtual form of itself~~
	*AKA virtual machine
	*provides some interfaces (APIs) that you can call (system calls that are available to
	~~applications to run programs, access memory and devices, and other related actions,~~
	~~aka standard library)~~
	*Resource manager - give programs resources based on priorities
	~~'''Goals:'''~~
	**High performance
	**Minimize overhead
	**protection between applications
	**Isolating processes
	**Reliability(runs nonstop)
	**Energy efficient
	**Secure
	**Mobility
	~~Unix~~
	*Has variants - linux, minux
	*Programmed in C
	~~Windows~~
	*VMS
	*Microsoft bought a team to build an operating system
	~~====Hello World - Sample Program====~~
	~~C programs start with '''main function'''~~
	~~[[File:Lec1-1.png\|none\|800px]]~~

	~~Compile and Run:~~
	~~[[File:Lec1-2.png\|none\|800px]]~~
	~~Two different ways to compile:~~
	*One does more work and it is smaller
	*One does less work and it is larger
	~~[[File:lec1-3.png\|none\|800px]]~~

	~~'''How many lines of code are running in a system?'''~~
	* 100 million lines of code!
	~~'''Questions to ask:'''~~
	~~#Who calls main?~~
	~~#Where do the arguments come from?~~
	~~#Who's taking the return value?~~
	~~#Who defines headers? Where do they come from?~~

	~~'''Mental Model'''~~
	*Don’t need to know exactly what happens
	*Know the strategy to figure it out
	*Know when to ask the questions
	*Know when it matters
	*OS → the code that runs under the application
	~~'''Who is in charge?'''~~
	*the '''first program''' that runs on the system is in charge
	**may delegate its powers to others
	*make sure it only obeys your commands (self preservation)
	**eg: if you get a command from someone else, ask me first
	**add a level of abstraction: authorization
	**downside: labour intensive (time consuming to approve every command)
	*create rules to determine when authorization is needed
	**when does the OS need to get involved
	**this is costly, so leave instructions behind so that is can make decisions
	**'''take charge of dangerous operations'''
	~~'''Cpu modes:'''~~
	*'''Supervisor mode''': access to all hardware resources
	*'''User mode''': access to limited resources, as defined by code running in supervisor mode
	~~'''Definitions:'''~~
	*Kernel: code that runs in supervisor mode (If your code runs in supervisor mode, you are
	~~in the kernel.)~~
	*Process: “running program” (Processes run in user mode)
	*System call: process making a request of the kernel (costly)
	*portable: able to work on different operating systems, a program that can run in many
	~~different environments.~~
	~~'''APIs'''~~
	*an application programming interface (API) is a set of subroutine definitions,
	~~communication protocols, and tools for building software~~

	~~'''Memory'''~~
	*read - address to access data stored there
	*write - address and data to be stored there
	*virtualizing memory - each process accesses its own private virtual address space
	**The OS maps this memory to the physical memory on the machine
	~~'''Concurrency'''~~
	*working on many things at once in the same program
	*multi-threaded programs
	**thread: a function running within the same memory space as other functions
	*race conditions
	~~'''Presistence'''~~
	*how do we not lose data
	*volatile - when the system crashes, the data in this memory is lost (DRAM)
	*hard drive - long term store
	*solid state drive - alternative for hard drive
	*file system - manages disk storage
	*handling system crashes
	**journaling or copy-on-write
	~~<center>'''END OF LECTURE 1'''</center>~~
	~~----~~

	~~=== Lecture-2===~~
	~~<center>'''Being revised!'''</center>~~

R.samanfar: /* Lecture-2 */

2018-09-12T08:01:04Z

Lecture-2

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	=== Lecture-2===		=== Lecture-2===
	<center>'''~~Comming Soon~~!'''</center>		<center>'''Being revised!'''</center>

R.samanfar: /* Lecture-2 */

2018-09-12T08:00:43Z

Lecture-2

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	=== Lecture-2===		=== Lecture-2===
			<center>'''Comming Soon!'''</center>

R.samanfar: /* Course Notes */

2018-09-12T08:00:10Z

Course Notes

← Older revision		Revision as of 08:00, 12 September 2018
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	If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.		If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.
	== Course Notes ==		== Course Notes ==
			=== Lecture-1 ===
	=== Lecture-1 ===

	====Introduction====		====Introduction====
	'''why is an operating system important?'''		'''why is an operating system important?'''

R.samanfar: /* Course Notes */

2018-09-12T07:58:43Z

Course Notes

← Older revision		Revision as of 07:58, 12 September 2018
Line 21:		Line 21:
	If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.		If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.
	== Course Notes ==		== Course Notes ==

	=== Lecture-1 ===		=== Lecture-1 ===

	====Introduction====		====Introduction====
	'''why is an operating system important?'''		'''why is an operating system important?'''

R.samanfar: /* Course Notes */

2018-09-12T07:57:36Z

Course Notes

← Older revision		Revision as of 07:57, 12 September 2018
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	If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.		If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.
	== Course Notes ==		== Course Notes ==
	~~<center>~~=== Lecture-1 ===~~</center>~~		=== Lecture-1 ===
	====Introduction====		====Introduction====
	'''why is an operating system important?'''		'''why is an operating system important?'''
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	*handling system crashes		*handling system crashes
	**journaling or copy-on-write		**journaling or copy-on-write
	<center>'''END OF LECTURE 1</center>		<center>'''END OF LECTURE 1'''</center>
	----		----

	=== Lecture-2===		=== Lecture-2===

R.samanfar: /* Course Notes */

2018-09-12T07:55:26Z

Course Notes

← Older revision		Revision as of 07:55, 12 September 2018
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	If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.		If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.
	== Course Notes ==		== Course Notes ==
	=== Lecture-1 ===		<center>=== Lecture-1 ===</center>
	====Introduction====		====Introduction====
	'''why is an operating system important?'''		'''why is an operating system important?'''

R.samanfar: /* Lecture-1 */

2018-09-12T07:54:56Z

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R.samanfar at 01:14, 12 September 2018

2018-09-12T01:14:53Z

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	=== Lecture-1 ===		=== Lecture-1 ===
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			=== Lecture-2===

R.samanfar at 01:14, 12 September 2018

2018-09-12T01:14:18Z

← Older revision		Revision as of 01:14, 12 September 2018
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	If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.		If you're not sure if something is appropriate to be added to the wiki, or you have a question about the bonus marks, ask Reza.
			== Course Notes ==
			=== Lecture-1 ===
			----