One Minute Evaluations for 23-25 September

CS 438 - Operating Systems Concepts

• Question: Do all of these techniques and methodologies apply to all types of OSs such as those for embedded systems?

  One minute response: The basic ideas apply, but the particular forms those ideas can take may differ significantly from one OS to the next. In particular, an embedded system operates in an environment that is considerably more restricted and controlled than the environment for a general-purpose OS. Embedded systems have more information about, and perhaps control over, their execution environment than do general purpose OSs, which lets embedded systems execute with more precision and accuracy. But an embedded system's objectives are also more well defined, and perhaps more restrictive, than are the objectives of a general-purpose operating system, making them harder to achieve.

• Topic: We talked about process management; simulation architecture and programs.

  Question: How do you maximize utilization while not creating starvation?

  One minute response: Admit processes by resource requirements and make sure one resource doesn't get overloaded by too many requesters.

• Topic: Schedules, processes + programs.

  Question: Nope.

• Topic: Learned about interrupts, single user systems, multiuser...

  Question: Hi.

  One minute response: Hi.

• Topic: We talked about how OS run user processed while still running itself.

• Question: The moving of data when interrupt occurs to where?

  One minute response: There's lots of data you could be asking about. The data that caused the interrupt has to be moved from the device to whichever process asked for it. The process-state data has to be moved to the processes table entry to clear space in the CPU for the interrupt code.

• Topic: CPU, memory, [?], single processes (def of processes), multiprocesses. Interrupts and [?].

• Topic: Programs, processes and how they OS handles them.

• Topic: We talked about single and multi-processes. The difference between programs and processes.

  Question: Why priority queues?

  One minute response: Because they make it easy to find the next process to run based on priority: it's at the head of the queue.

• Topic: We discussed the OS that we will be using for our projects. We will not be building our own. Single-user OS, multi-user.

  Question: How did Windows go from single user to multi?

  One minute response: Painfully. Roughly, Windows ME and earlier were single-user OSs with a creaky and egregious array of hacks to make it behave sorta like a multi-user OS, if your standards and expectations weren't to high. The NT (new technologies) project started in the late 80s to write a true multi-process OS. They hired the architect of Digital's VMS (virtual memory system) OS to lead the project (which is why Bill Gates is a genius: he saw, as no one else saw, that what the world was really crying out for was a re-write of VMS).

• Topic: The project; architecture of "system".

  Question: Were we actually assigned any programming work to do on the project yet?

  One minute response: No, not yet.

• Topic: We learned about processes and how the processor can handle who gets what when.

  Question: Why would stack entry (lifo) be of any use or fair?

  One minute response: It wouldn't be fair in the usual sense. It would be useful in systems where there are a few long running processes and many short lived (or burst-executing) processes. The short-lived process on the top of the stack are expected to quickly clear the stack, exposing the longer-lived processes underneath. The stack makes sure the short-lived processes are not too far from the CPU.

• Topic: CPUs, processes, priorities, memory, registers, interrupts, OS. vs. User mode.

  Question: Can there be more than one OS and user at the same time?

  One minute response: Yes, for both. We'll talk about multi-user systems next week. Using the idea of a virtual machine, you can also run several OSs at the same time on the same hardware. IBM, for example, has a flashy demo where they have one of their mainframes run 41,000 copies of Linux.

• Topic: We talked about resource management and single vs. multitasking OS.

This page last modified on 16 July 2003.