Chapter 1 - Part 2 Flashcards
Why was Posix created, and by whom?
Multiple different Unix systems were competing at the time, and were starting to develop different standards. Posix was created by the Institute for Electrical and Electronics Engineers (IEEE) to help set forth a set of standards for compatibility reasons.
What was the name and company of the operating system Unix was derived from, in what year was it named ‘Unix’, and when was it first released?
Honeywell’s Multics OS, it was named by Brian Kernighan in 1970, and it was released in 1974.
What is the mechanism for interleaving instructions from multiple processes on a single processor called?
context switching
What is the OS abstraction for giving a program the illusion that it has exclusive access to the CPU, memory, and I/O devices?
processes
What is a context in terms of an OS process?
All state information that process needs to run.
What is a system call?
When a process passes control to the operating system.
What is the kernel in an OS?
The part of the OS that is always resident in memory.
Is the kernel of an OS a process?
No, it is a collection of code and data used to manage processes.
How is a thread different from an OS process?
Threads are an execution unit within a process, processes are controlled and managed by the OS. Threads share memory, processes do not.
Summarize Amdahl’s law.
When one portion of a system is sped up, its effect on the overall speed of the system depends on how significant it was and by how much it was sped up.
If a component is doing 40% of the work in a system, and it receives a speedup of 5 times, write the equation that represents this speedup using Amdahl’s law (using bc).
scale=10; 1 / ((1 - .4) + .4 / 5)
What formula describes the ratio of performance improvement?
t-old / t-new
Improving from a time of 10 hours to a time of 5 hours is 10/5, a 2 times speedup.
