GATE CSE 2023: Question Number 27 1 Master Paper: Question 17 Figure 1: Question Description Screenshot from the master question paper GATE Answer Key: (A),(C),(D) My Opinion: Answer could be any of ( A, C, D ) or ( C, D ) and Students who marked ( A, C, D ) or ( C, D ) should be rewarded. My opinion aligns with the given answer except for one option, which is ( A ) FCFS. In my opinion, whether to include or exclude FCFS in the answer hinges on a single, specific assumption. 1 2 Default Assumption about jobs being submit- ted FCFS operates on the principle of First In First Out. If the first job submitted by a user runs an infinite loop (e.g., ”while(1);”), it will prevent other processes from executing and cause starvation. Despite the validity of the argument mentioned, There are multiple additional standard sources that claim FCFS does NOT undergo starvation. Kindly refer to Figure 2 , which is a screenshot taken from Page 432 of William Stalling’s book. Figure 2: Page 432 of William Stalling’s book “Operating Systems: Internals and Design Principles” Similarly there are lots of other sources saying that FCFS does not have star- 2 vation: ( 1 ) Carnegie Mellon University lecture notes: Reference URL: https://www.andrew.cmu.edu/course/15-440-sp10/applications/ln/lecture7.html Statement mentioned about FCFS: ”This algorithm is very easy to imple- ment, and it is also very fair and consequently starvation-free.” ( 2 ) Washington University lecture notes: Reference URL: https://courses.cs.washington.edu/courses/cse451/15wi/lectures/pdf/10- sched.pdf Statement mentioned about FCFS: ”jobs treated equally, no starvation...” ( 3 ) Lecture notes by IIT Kanpur: Reference URL: https://ict.iitk.ac.in/wp-content/uploads/CS330-Operating- Systems-lec03.pdf Statement mentioned about FCFS: ”This algorithm is very easy to imple- ment, and it is also very fair and consequently starvation-free.” ( 4 ) IIT Bombay Lecture Slides: Reference URL Page 10: https://www.cse.iitb.ac.in/ rkj/cs347/additional/lectures/scheduling.pdf Statement mentioned about FCFS: ”Starvation free.” In my view, the only foundation upon which all these sources support the idea that FCFS is not vulnerable to starvation is their supposition that jobs with infinite burst time are not submitted. Which means all of these sources assumed that burst time is finite. The assumption that only finite burst time jobs occur is so common that nu- merous authors consider it a default assumption. William stalling’s book and other sources has taken following assumption as default: Default Assumption: Users are nice and will submit only finite burst time jobs. 3 3 Same question in different universities Now, Please consider the question in Figure 3 taken from University of Cal- ifornia Irvine (UCI). Figure 3: Question taken from University of California Irvine (UCI) homework Reference of UCI homework question in Figure 3 can be found at: https : //www.ics.uci.edu/ ardalan/courses/os/homework/HW 2 s olutions.pdf The question they posed at UCI is identical to GATE CS 2023 Question 17, with the exception that they explicitly included the assumption of infinite pro- cess burst time. Please find one more identical question in Figure 4 This is taken from Univer- sity of Buffalo. 4 Figure 4: Question taken from University of Buffalo Midterm Reference of Figure 4 can be found at: https : //cse.buf f alo.edu/f aculty/tkosar/cse 421 − 521 f all 2012 /slides/ 12 − M idterm R eview.pdf It is worth noting that University of Buffalo has not explicitly stated an as- sumption about processes having infinite burst times, they have not taken FCFS scheduling into account for the possibility of starvation. In the answer to the first question, FCFS was included because the question explicitly stated that jobs with infinite burst times were permitted. In contrast, the second question did not provide any explicit mention of burst time and instead implicitly assumed that jobs have finite burst time, which is why FCFS was not mentioned in the answer. 4 Exact Same question in Galvin’s book Kindly review the identical question depicted in Figure 5 of Galvin’s 7th edition of Operating System Concepts. 5 Figure 5: Question taken from Galvin’s 7th edition of Operating System Con- cepts, Page No. 187. Galvin’s Solution manual also does not contain FCFS as the answer to the above question. Figure 6: Solution taken from Operating System Concepts 7th edition Solution Manual at Page No. 30. Reference of Figure 6 can be found at: https : //www.academia.edu/ 8396518 /Operating S ystem C oncepts 7 th e dtion S olution M anual 6 5 Final Remark In conclusion, I’d like to state that the assumption of jobs having finite burst times is so common that it is accepted as the default unless otherwise stated. A number of the candidates provided answers to the question based on the implicit assumption that processes are limited to having finite burst times, which led them to believe that there would be no starvation in FCFS (as per William’s book). Meanwhile, other candidates marked options A, C, and D, taking into account the possibility of infinite burst time. As the question does not explicitly mention infinite burst time, it is unclear whether to take the default assumption (of finite burst time) or not. Therefore, both answers are possible. Hence, I am kindly requesting you, to please change answer key and include both possibilities (A,C,D) (C,D) in answer. 7