This article provides study material and solved assignments on Operating System. It covers topics such as arm movement diagrams, deadlock conditions, file management, and more.
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Running head: OPERATING SYSTEM Operating System Name of the student: Name of the University: Author note:
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1 OPERATING SYSTEM Table of Contents B. Q1..........................................................................................................................................2 a) Arm movement diagrams...................................................................................................2 b) Head movement calculations.............................................................................................4 B.Q2...........................................................................................................................................5 a) Deadlock Conditions..........................................................................................................5 b) Deadlock Situation.............................................................................................................7 c) File Management................................................................................................................8 B. Q3..........................................................................................................................................9 a).............................................................................................................................................9
2 OPERATING SYSTEM B. Q1. a) Arm movement diagrams 1734126312196123 FCFS Arm movement diagram
3 OPERATING SYSTEM SSTF Arm movement diagram
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4 OPERATING SYSTEM LOOK Arm movement diagram b)Head movement calculations FCFS Total head movements: (40-17) + (17-34) + (34-1) + (1-26) + (26-3) + (3-12) + (12-19) + (19-61) + (61-23) = 23+17+33+25+23+9+7+42+38 =217 Average head movements:217/9 =24.111 SSTF
5 OPERATING SYSTEM Total head movements (40-34) + (34-26) + (26-23) + (23-19) + (19-17) + (17-12) + (12-3) + (3-1) + (1-61) = 6+8+3+4+2+5+9+2+60 =99 Average head movements:99/9 =11 LOOK Total head movements (40-61) + (61-34) + (34-26) + (26-23) + (23-19) + (19-17) + (17-12) + (12-3) + (3-1) = 21+27+8+3+4+2+5+9+2 =81 Average head movements:81/9 =9 B.Q2. a) Deadlock Conditions In operating systems and concurrent computing, deadlock is referred to a system where each of the members of a group of processes are waiting for resources to be allocated, which are already allocated to other processes [7]. These processes are in-turn waiting for other resources. In other words a when a process enters into an ever-lasting waiting state when their coveted resources are held by other process, deadlock occurs [4]. There are four prime reasons that lead to a deadlock in a multiprocessing system environment. They are as follows:
6 OPERATING SYSTEM 1.Mutual exclusion: When at least one of the resources are held by a process in a non- sharable mode. This prevents the resource to be utilized by other process while one process is already working on it. 2.Hold and wait or resource holding: When a process is holding on to one resource and is waiting for another resource to be allocated which in-turn is waiting for other resources to be released. 3.No pre-emption: Only the process that is holding onto a particular resource can voluntarily release it on completion [4]. 4.Circular wait: When each of the process within a particular working frame is waiting for another resource to be released.Generally, considering asetof waiting processes such asP= {P1,P2,…Pn}, whereP1is waiting for the resourceR1that is held byP2. P2is waiting for the resourceR2that is held byP3and so on. This continues untilPnis waiting for the resourceRnthat is primarily held byP1. This is a typical example of a deadlock situation due to Circular wait. In this above example, process P1 is holding R1 and waiting for resource R2 whereas P2 is holding R2 and waiting for P1 to release R1.
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7 OPERATING SYSTEM b) Deadlock Situation The above resource-allocation graph depicts a simple deadlock situation that has been bred up in a system with 4 processes (P-A, P-B, P-C and P-D) and 5 different resources or devices by the identifier (D1, D2, D3, D4 and D5). In this scenario, it is clear that a deadlock prominently exists. Here, process P-A is waiting for device D1 whereas D1 is assigned to process P-B. P- B is holding onto D1 and in-turn waiting for device D3 to be released by P-C that is holding onto D2. P-B and P-D needs to two separate devices to complete their tasks. P-B is therefore holding onto a device D5 that is being requested by P-D. P-D has one resource held and hence it is requesting two other resources and hopes to get one of them. D3 is being requested by P-C but it is currently assigned to P-D which is also waiting for D4 and D5 that are allocated and held up by P-A and P-B respectively. P-B will not release D5 unless it is allowed access to D2.
8 OPERATING SYSTEM Therefore, as it can be seen from the above scenario, none of the process will agree on leaving the devices or resources that they are holding onto unless they are assigned their wanted device. This will create a deadlock in the system. c) File Management I) The fmt command is used in LINUX as a formatter for the process of simplifying or optimizing the texts in a file. Files can be formatted in terms of their width or length. The fixed length technique is to implement the commandfmtitself. This will format the text in the file such that all one characters are out in the same line. The width option is used when the number of characters to be put per line is needed to be mentioned [6]. Syntax: fmt –w VALUE FILE_NAME This will format the file such that the texts are broken to form new lines with VALUE number of characters per line. II)Complete or absolute file naming is the process of providing the entire details of the path that leads to the file. Therefore, the naming starts at the root directory and travels into the sub-directories unless it reaches the file to be identified. The directories are traversed in the naming convention with the help of / symbols. Relative file or path names are those that do not require the assistance of the complete path value to spot a directory or file. A relative path is generally characterized by naming convention that does not start with a /. This signifies that the file naming has been initiated from the current directory [1]. Example:
9 OPERATING SYSTEM In this above path structure, considering that Home is the current working directory. The naming conventions for the file Work will be as follows. Complete File name:/home/jono/work Relative File name:jono/work B. Q3. a) chmod command This UNIX command is used to change the system permissions on certain file system objects within a certain directory [2]. It may also be used in order to alter certain mod flags. It is an abbreviation used for the purpose that it server, “Change mode”. Syntax:
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10 OPERATING SYSTEM chmod [Options]... Mode [,Mode]... file... chmod [Options]... Numeric_Mode file... 4 = r (Read) 2 = w (Write) 1 = x (eXecute) chmod [Options]... --reference=RFile file... Eg 1: chmod 751 myFile.txt This means User will have Read, Write and Executable permissions. Group will have Read and Execute permissions. Others will only have Executable permissions. Eg 2: chmod u=rwx, g=rx, o=x tech This option helps to sets the modes manually where r=read, w=write, x=exc Screenshot: grep command The grep command in UNIX is used to search for a particular pattern of text within the text of a specified file.
11 OPERATING SYSTEM Syntax:grep [options] patternText [file or files] Some major Options: -c : This prints only a count of the lines that match a pattern -w :Match whole word -i : Ignores, case for matching Eg1: grep -i "BoY" myFile.txt This will search for the String “boy” inside the file having ignored the alphabetical case. Eg2: grep -w "Boy" myFile.txt This will search for the String “Boy” inside the file and it must be present as an entire word. Screenshots: ls command This command helps to list out all the files and directories that exists within the particular working directory with required details.
12 OPERATING SYSTEM Syntax: ls [option] [file] Eg1: ls –l This command will print out all the necessary information of the directory or files specified. Eg2: ls This command will display only the files and directories [5]. Screenshots: mkdir command The mkdir command allows to create a new directory within the current working directory [8]. Syntax: mkdir directoryName Screenshot:
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14 OPERATING SYSTEM References [1] Yerima, Suleiman Y., Sakir Sezer, and Igor Muttik. "High accuracy android malware detection using ensemble learning."IET Information Security9, no. 6 (2015): 313-320. [2] Chirigati, Fernando, Rémi Rampin, Dennis Shasha, and Juliana Freire. "Reprozip: Computationalreproducibilitywithease."InProceedingsofthe2016International Conference on Management of Data, pp. 2085-2088. ACM, 2016. [3] Kim, Sangman, Michael Z. Lee, Alan M. Dunn, Owen S. Hofmann, Xuan Wang, Emmett Witchel, and Donald E. Porter. "Improving server applications with system transactions." InProceedings of the 7th ACM european conference on Computer Systems, pp. 15-28. ACM, 2012. [4]Li,ZhiWu,NaiQiWu,andMengChuZhou."Deadlockcontrolofautomated manufacturing systems based on Petri nets—A literature review."IEEE Transactions on Systems, Man, and[5]Cybernetics, Part C (Applications and Reviews)42, no. 4 (2012): 437- 462. Abradi,Sam,IanNaval,andFredricSilberberg."AugmentedUnixUserland."Major Qualifying(2015). [6] Shotts Jr, William E.The Linux command line: a complete introduction. No Starch Press, 2012. [7] Silberschatz, Abraham, Peter Baer Galvin, and Greg Gagne.Operating system concepts essentials. John Wiley & Sons, Inc., 2014. [8] Gamma, Erich, Richard Helm, and John Vlissides. "Design patterns applied."