OS

Question 1

sharing resources across users/programs by taking turns(time share)

Answer 1

Multiplexing

Question 2

sharing resources by dividing them up (space share)

Answer 2

Space multiplexing

Question 3

_____ connects the CPU/memory/I/o devices

Answer 3

System bus

Question 4

software that runs in kernel mode (mostly). It manages all the hardware and provides programmers an interface to manage hardware. They have a user mode and kernel mode

• Processes
• Memory management
• I/o device management

Answer 4

Operating system (OS)

Question 5

Processors (CPU) fetches instructions from memory and runs it. They have registers. Can execute more than one command at a time using a pipeline.

What are the 3 main steps that repeat?

Answer 5

-fetch
-decode
-execute

Question 6

____ fetches instructions from memory and runs it

Answer 6

Processors

Question 7

they store data locally to speed up processing

Answer 7

Registers

Question 8

A type of register. memory address of next instruction to fetch

Answer 8

Program counter

Question 9

(register) - points to the current stack in memory. Holds input parameters, local variables, and temp variables that are not kept in general registers.

Answer 9

Stack pointer

Question 10

User programs run in ______ (which can only use a subset of the available instructions)

Answer 10

user mode

Question 11

a user program makes a _______ ____ to invoke the OS

Answer 11

system call

Question 12

____ allows the CPU to hold the state of different threads and switch back and forth at a nanosecond time scale

Answer 12

Hyperthreading

Question 13

Memory Types
These are in order of fastest to slowest:

Answer 13

1. Registers (no delay in access)
2. Cache (L1/L2)
3. Main memory
4. SSD/hard drive

Question 14

____ _____ have a penalty of tens to hundreds of cycles when being accessed.

Answer 14

Cache misses

Question 15

Which cache is faster? L1 or L2?

Answer 15

L1
is faster, but also much smaller in size (8 KB to 64 KB)
Located on the processor chip

Question 16

______ a container holding all the info needed to run a program.

What are things are contained in it?

Answer 16

Process

Holds:

• Address space (memory location where it can read/write)
• Executable program, data, and its stack
• Registers, program counter, stack pointer
• Open files
• Related processes
• Outstanding alarms

Question 17

An array that holds info about each process

Answer 17

Process Table

Question 18

used to request that data is retransmitted over the network when a process doesn’t get a response

Answer 18

Alarm Signal

Question 19

___ are the software version of hardware interrupts

Answer 19

Signals

Question 20

Alarm Signal

Answer 20

used to request that data is retransmitted over the network when a process doesn’t get a response

Question 21

Memory that holds executing programs

Answer 21

Address Space

Question 22

___ is done when one program is moved out of the address space so another program can be moved there (to the main memory).

Answer 22

Swapping

Question 23

___ can connect two processes. Note that processes in the ___ expression may all be started at once, but they’ll be set to blocked until their input is ready

Answer 23

pipe

Question 24

_______ ___ are the file read write and execute numbers. Ex: 640

Answer 24

Protection bits

Question 25

Sh, csh, ksh, bash, zsh. These are each _____

Answer 25

shells

Question 26

Which call can use the kernel? Procedure call or system call?

Answer 26

System calls

Question 27

A built-in bash command that is used to execute a command when the shell receives any signal is called a ___. It can respond to signals

Answer 27

trap

Question 28

List the name of some common signals

Answer 28

SIGINT - means a process was interrupted SIGKILL/SIGTERM - a process was explicitly killed by the kill program SIGCONT - If a process has been paused by sending it SIGSTOP then sending SIGCONT to the process wakes it up again SIGXCPU- happens if a process exceedes it's CPU limit

Question 29

Where is the L2 cache located? How big is it?

Answer 29

On the mother board Size: 256 KB to 16 MB

Question 30

The operating system has a _____ to run commands. Then it has a __ __ _____to return control to the program that needed the OS to do work. Note that these live in the kernal space.

Answer 30

dispatcher sys call handler

Question 31

Portable Operating System Interface has 100 procedure calls

Answer 31

POSIX

Question 32

______ - Only way to creat a new process in posix - Creates an exact duplicate of a process, including all files, descriptors, registers, etc. - After that, changes to each process are independent - Returns the PID (process id)

Answer 32

Fork

Question 33

____ __ _____ Two processes share a space in memory until a change is made, then a copy is created.

Answer 33

copy on write

Question 34

The ______ _____ contains these three segments: - Text segment (code) - Data segment (variables) (grows up) - Stack (grows down)

Answer 34

processes memory

Question 35

What does L2 cache store?

Answer 35

It stores data and instructions that are not currently being accessed by the processor, but that may be needed in the near future

Question 36

Where is L1 cache located?

Answer 36

On the processor (CPU)