Operating Systems (Final)

Question 1

File System

Answer 1

A way to organize and manage files on a storage device.

Question 2

File System Components

Answer 2

Files, FCB’s, directories, and hardware/software used to implement the secondary storage.

Question 3

Speed of Secondary Storage

Answer 3

Secondary storage is much slower than CPU and main memory, but still faster than disk drives and tape drives (I/O stuff)

Question 4

Random Access of Sec Storage

Answer 4

CD writers, Hard Drives

Question 5

Sequential Access of Sec Storage

Answer 5

Tape Drives

Question 6

Seq. vs Random Access

Answer 6

Sequential is faster! Its cheaper too! However, what is best depends on the situation. It is more effective to use random access when dealing with a large database, because otherwise the entire database would have to be loaded in sequential.

Question 7

Indexed Files

Answer 7

A file with an index that allows easy random access, if the computer is given the index.

Question 8

FCB

Answer 8

File Control Block. Holds file metadata. Can include: name, owner, date, path, type, and more properties.

Question 9

Seek()

Answer 9

Place file pointer at a location in bytes. Used to navigate a file. Can be used by index files to retrieve the location to specific records even faster.

Question 10

Tell()

Answer 10

Return current byte location. Used to navigate a file. Can be used by index files to retrieve the location to specific records even faster.

Question 11

chmod 666 a.out error

Answer 11

Running a.out with those permissions set is impossible. 666 means read and write permissions is given to everyone, but not execution permissions. Give execution permissions to fix it (done with +x).

Question 12

Disk

Answer 12

A drive with a spinning disk where data is written and read by a disk head.

Question 13

Track

Answer 13

A ring on the disk.

Question 14

Sector

Answer 14

A piece (like a slice) on the disk.

Question 15

Block

Answer 15

A logical unit of storage on the disk, located by a specific track/sector.

Question 16

Contiguous versus linked allocation

Answer 16

Files must be allocated in a contiguous manner, while in linked allocation, files can be anywhere, as blocks point to other blocks until the last block in the file reads EOF.

Question 17

Linked allocation benefits

Answer 17

There is much less fragmentation, Dynamic allocation, and easier file expansion.

Question 18

FAT benefits

Answer 18

It is better than linked allocation because all linking information is held in a separate table, instead of it being tied to the blocks. The table is also stored in cache memory.

Question 19

How is block size determined?

Answer 19

By factors such as the size of the disk, the size of the files to be stored, and system performance requirements all play a factor.

Question 20

Logical to physical mapping of blocks

Answer 20

Contiguous, linked, and multi-indexed allocation. Any of these schemes can be used to translate blocks, but it depends on the storage system requirements.

Question 21

FCSF Disk Head Algorithm

Answer 21

Serves read/write requests in the order they are received.

Question 22

Shortest Seek Time First

Answer 22

Serves requests by shortest seek time.

Question 23

Scan

Answer 23

Services requests in a single direction, it reverses and serves the requests in the other direction.

Question 24

Cyclic Scan

Answer 24

Similar to scan, but instead of reversing direction, it starts back at the beginning of the disk before continuing.

Question 25

Security

Answer 25

A system is secure if its resources are used as intended under all circumstances.

Question 26

Physical Threats

Answer 26

Put systems in well-protected places! Flood, fire, lightning, etc are all dangerous.

Question 27

Human Threats

Answer 27

Certain people should have access and must be screened beforehand. Levels of security.

Question 28

Password Threats

Answer 28

Passwords can be compromised by multiple ways.

Question 29

Password Guess

Answer 29

Know something about the person, or past passwords.

Question 30

Accidental Exposure

Answer 30

Looks over shoulder.

Question 31

Illegal Transfer

Answer 31

Spying

Question 32

Legal Transfer

Answer 32

Here's my password! Here's my friends password! ....

Question 33

Password Encryption

Answer 33

Done by 2 stage hashing, stored in password file.

Question 34

More Software/Security Vulnerabilities

Question 35

Shared Memory Multiprocessor

Answer 35

Large memory with multiple cpus.

Question 36

Memory passing multi-computer

Answer 36

A connection allows for multiple cpus to be connected with their own memory.

Question 37

Wide Area Distributed

Answer 37

Internet shares multiple computers

Question 38

High bus load

Answer 38

Multiple cpus all sharing memory on a bus.

Question 39

No private memory

Answer 39

Multiple cpus each have their own cache sharing memory on a bus

Question 40

Private memory with lower bus load

Answer 40

Multiple cpus on a bus with cache memory and private memory using a shared memory.

Question 41

Problem with CPUs with its own OSs

Answer 41

Have to share a copy of the same OS. Private data has to be stored on the individual memory.

Question 42

Problem with each OS scheduling processes.

Answer 42

A user can use a CPU and stay there w/o sharing any memory or resources. Solved by using a master CPU.

Question 43

Symmetric Multiprocessing

Answer 43

Run a shared OS Process with multiple cpus. The shared memory has a set of semaphores with the shared OS process.