Enums, Sockets, Threads

Question 1

Define what an Enumeration is, as well as it’s purpose…

Answer 1

A way of specifying a set of integer constants, each of which is represented by a variable name.

Question 2

What is the default start value of Enums? What happens if you assign a different integer to the first value?

Answer 2

0. If the first number is changed, the following numbers will be be incremented accordingly.

Question 3

In an enum of 10 members, if the first 5 constants are 0-5 integers, but then the 5th is changes to 88. What will the integer constants of 5 to 10 be?

Answer 3

88,89,90,91,92

Question 4

Write a small program to give an example of an Enumeration…

Answer 4

…

Question 5

What does the telnet command do? Give an example of telnet in use…

Answer 5

telnet connects the terminal to a remote server e.g. telnet computerscience.ac.uk 80

Question 6

Define the roles of sockets on a network…

Answer 6

Sockets enable nodes (hosts) on a network to communication with each other.

Question 7

In most systems that use sockets, what language is the fundamental low-level socket that peripheral sockets all filter down to developed in?

Answer 7

Most systems have a core C socket, which other sockets filter down to.

Question 8

What are the 2 sides of a Socket interaction across a network called?

Answer 8

Client Server.

Question 9

What are the 7 steps that a Server Side socket conducts to interact with a Client Socket?

Answer 9

Create socket; set socket options; Bind listener to port number; Listen; Accept client request; Exchange data; Close connection.

Question 10

What are the 3 steps that a Client Side socket conducts to interact with a Server socket?

Answer 10

Create socket; Request a connection; Exchange data.

Question 11

When a Server Socket is listening on a port, what type of process is doing the listening?

Answer 11

Http Daemon process listens for connection on the socket port.

Question 12

What is a daemon process in Linux?

Answer 12

A background process

Question 13

Which of the fundamental processes is used to enable data exchange between the 2 sockets?

Answer 13

Pipe

Question 14

Which command is used to create a pipe between a pair of sockets?

Answer 14

popen( ) -> Pipes between 2 sockets.

Question 15

With regards to exchanging data, what is the difference between using pipes as opposed to raw sockets?

Answer 15

Using popen( ) opens a buffered stream between sockets. Thus, it’s safer and quicker.

Question 16

Since C doesn’t have native threading, which API does it use or threading?

Answer 16

POSIX -> Portable OS Interface

Question 17

What is pthreads? Where is it utilised?

Answer 17

pthreads is a multi-threading model used by many modern languages, and exists independently of any language.

Question 18

Which statement would be used to declare 3 threads?

Answer 18

pthread_t -> e.g pthread_t my_threads(3);

Question 19

What is mutex? What problem does it solve? What issue can it cause?

Answer 19

Locks a resource so only 1 thread can execute on it at any given time. However, Causes idle time for waiting threads.

Question 20

What signalling mechanism do we use to signal that a resource is free for a thread to use?

Answer 20

Semaphore

Question 21

What value does semaphore return to indicate that the resource is free?

Answer 21

Non-zero. If the semaphore returns a non-zero value, the resource is free.