CSC 213, Fall 2006 : Schedule : Discussion Questions for 8/28

Discussion Questions for 8/28

Concurrent and parallel execution

The book states that concurrency occurs when it "appears" that 2 or more programs are running at the same time, or when they are "really" running at the same time (parallel execution). But later on the author writes "Concurrent and parallel execution are related to the notion of resource sharing..." I thought parallel execution is a kind of concurrent execution. Is there a subtle difference between parallel and concurrent execution? (Monica)
Nutt explains that "a system supports concurrent execution when either it appears that two or more programs are being executed simultaneously, or they really are executing at the same time" (p. 11). The first part of the author's statement is clear, but the latter part appears almost identical to his definition of parallel execution--he explains that parallel execution exists between "true simultaneous operations" (p. 11). It seems to me that if two programs are really executing at the same time, then they are true simultaneous operations. In that regard, could you please clarify the distinction he is drawing between the two kinds of execution? (Angeline)

How does the operating system create an abstract machine? Are there a fixed number of abstract machines in every computer? (Monica) [We'll discuss this more in Chapter 6.]
On page 14, Nutt uses the car wash analogy to demonstrate how multiprocessing may improve overall system performance. Is his claim about improved performance founded on the assumption that the order of instructions ensures minimal or no stalling within the pipeline? Can't multiprocessing hurt performance if the ordering of processes is such that certain processes depend on the results of yet-to-be-completed preceding ones? (Angeline)
Could you clarify the distinction between viewing a process as a "job" and a "program in execution," and what the difference means for OS programmers? (Lorelei)
In batch processing systems, could the behavior of one job depend on the output of previous jobs? (Cable)

Are transparent resource sharing and explicit resource sharing meant to be implemented in tandem? (Mike)
What is the role of explicit resource sharing in a timesharing OS? (Mike)
Can multiprogramming be used efficiently in situations where one short task must wait on a longer one, both requiring the same resource? How does thread priority work? (Nick)
Section 1.1 (p.17) says that contemporary OS are constructed as "trusted software". Are there certain criteria that an OS system has to fulfill to be given that term or does it merely describe an understanding between a vendor and a customer that the OS should be trusted as it is "required to perform exactly as intended" for the system to behave correctly? (Saugar)

In my experience, UNIX based operating systems (e.g. every Linux flavor) are used in the same capacity as any Windows OS. In the reading, however, the author differentiates the two by using UNIX as a Timesharing strategy and Windows as a PC/Workstation strategy. What makes UNIX more of a Timesharing example and Windows less so? (Luis)
Along the same lines. What is the difference between a workstation being used by many different users (e.g. one through ssh and two alternating signing on and off) and a strict Timesharing strategy? Are they handled exactly the same by the two strategies of Operating Systems? (Luis)

If OS is closest to hardware, what thing can compile OS? or I am asking how OS is written? (Sheng)
On page 27, Nutt mentions the persisting of BIOS in today's computer. How did BIOS software influence the design of OSs and did recent OS designs affect BIOS designs? Does BIOS programming consider a part of OS programming? (Chayapan)
Our book mentioned that IBM's BIOS system is an early operating system. Now, DOS and Windows 3.1 for sure used the BIOS to access hardware, while later versions of Windows (specifically the NT family) use their own drivers. How does BIOS relate to both systems (DOS and Windows NT)? Does DOS run on top of BIOS or beside it? Does Windows NT run on top of BIOS or does BIOS end when Windows begins? (Chris) [We'll come back to this in section 4.6.]
In all of the book's diagrams, the OS is separate from the window manager and other systems software. This is valid for most *nix systems in the separation of the kernel, desktop environment, and (in some cases) window manager, but it does not account well for Windows NTs and Mac OS X, which integrate most (if not all) system software with the OS. What are the benefits/pitfalls of this integration, and how does it fit in to our overall view of operating systems? (Chris) [Can a web browser be part of an operating system?]

[May discuss if time] How has the Internet influenced the way OSs are designed? (Nick)
[For next time] What is threading, and how is it different from a process? (Heather)
Did batch processing systems support flow control, e.g. "run job X Y times", as current scripting languages do? (Cable)
When reading about space and time-multiplexed sharing I could not help but question whether the new processors that use Intel Core Duo technology implements time-multiplexed sharing among more processes at a given time than the single core technology or is there some space-multiplexed sharing involved? This new technology claims to be more energy efficient that keeps the computers cooler and quieter. Does either the space or time-multiplexed sharing have to do anything with power consumption? (Saugar)

Created August 27, 2006
Last revised August 27, 2006