Transcript class16_hw_os

HW & Systems:
Operating Systems
COMP101
Computational Thinking and Design
Tuesday, October 21, 2014
Carolyn Seaman
Susan Martin
University of Maryland, Baltimore County
Wherefore OS?
 A “naked machine” has no tools or programs to help
the user
 Write instructions in binary
 Write data in binary
 Load instructions into memory one cell at a time
 Initiate program run
 Too difficult for humans to do
 We must build an interface to hide the details and make
the computer easier to build
 The OS is an abstraction of the machine that keeps
users and programmers from having to think about the
low-level hardware details
Virtual Machine (abstraction!)
Naked machine:
Virtual machine (OS):
1. Write program in binary
1. Write program using text
2. Load instructions oneby-one into memory
3. Insert start into memory
address 0 and push “go”
button
4. Read results from
memory one-by-one, in
binary
editor in high-level
language
2. Save program to folder
3. Use translator to convert
to binary
4. Use scheduler to load
and run
5. Use I/O system to print
results
Operating Systems
 Schedule processes and pieces of processes
 Manage resources (data, I/O devices)
 Give users and programmers easier ways to make the
computer work
Deadlock
 Safe use of resources: ensure that computer doesn’t get
stuck in deadlock
 Multiple programs requesting access to resources
 Deadlock occurs when all programs have some resources,
and are waiting for resources held by others
 Deadlock prevention: if you can’t get all resources, release
all you have and try again later
 Deadlock recovery: if no acknowledgement, send message
again
It’s time for…
OS
Jeopardy!!!!!
Rules
 All questions and answers come from the assigned reading
or the first part of this lecture
 I’ll show you an answer, you have to come up with the
question
 If your team knows the question, one person needs to stand
up
 If I call on your team, someone DIFFERENT from the person
who stood up has to give the question
 If I call on your team, you must answer within 5 seconds
 No team can respond twice in a row
Answer: Operating system.
Question: What does OS stand for?
Answer: A core component of the
operating system that coordinates all
other programs
Question: What is the kernel?
Answer: One is static and written down,
the other is dynamic and running.
Question: What is the difference between
a process and a program?
Answer: One has its own address space
and the other shares an address space
with other entities of the same type.
Question: What is the different between a
process and a thread?
Answer: It lets processes act as if there
is more memory available than there
actually is.
Question: What is virtual memory?
Answer: When the kernel switches back
and forth between programs, giving each
its turn with the CPU.
Question: What is multitasking?
Answer: Because it keeps users and
programmers from having to think
about the low-level hardware details of
the computer they’re working with.
Question: How is an OS an abstraction?
Answer: Process management, memory
management, file system management,
network and device management
Question: What are the main functions of
the kernel?
Answer: This occurs when all running
processes have some resources (e.g.
I/O devices), and are waiting for
resources held by others.
Question: What is deadlock?
Answer: If a process can’t get all the
resources it needs, it must release all
the resources it has and try again later.
Question: How can you prevent
deadlocks?
Answer: What the kernel does when a
process’s time slice expires.
Question: What is interrupt?
Answer: When a process is stuck waiting
either for data or for a device to be
available.
Question: What is I/O bound?
Answer: When the kernel swaps out the
context of one process for the context of
another.
Question: What is context switching?
Answer: round-robin, FIFO, priority-based,
shortest-time-remaining
Question: What are some scheduling
policies that could be implemented by a
kernel?
Answer: CPU utilization, average
latency, throughput, fairness
Question: What are some ways to
measure the efficiency of the CPU?
Answer: A computer without an
operating system.
Question: What is a naked machine?