On the local machine, create a folder to hold a1:
=================================================
ilir@ilir-MacBookPro:~$ cd csc207repos
ilir@ilir-MacBookPro:~/csc207repos$ mkdir a1
ilir@ilir-MacBookPro:~/csc207repos$ cd a1
ilir@ilir-MacBookPro:~/csc207repos/a1$

Check out your repo in Markus:
===============================
ilir@ilir-MacBookPro:~/csc207repos/a1$ svn --username dema co https://markus.cdf.toronto.edu/svn/csc165-2016-01/c5dema
A    c5dema/Test
A    c5dema/Test/file.txt
Checked out revision 2.
ilir@ilir-MacBookPro:~/csc207repos/a1$ 

Go to the root of the repo:
===========================
ilir@ilir-MacBookPro:~/csc207repos/a1$ cd c5dema/Test
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ ls
file.txt
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ 

Modify the existing file file.txt and add a new file file.txt:
==============================================================
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ vi file.txt
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ vi file1.txt
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ 

Check out the status, commit changes, and check the status again:
=================================================================
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ svn status
M       file.txt
?       file1.txt
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ svn add file1.txt
A         file1.txt
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ svn commit

Log message unchanged or not specified
(a)bort, (c)ontinue, (e)dit:
a
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ svn commit -m "Latest changes"
Sending        file.txt
Adding         file1.txt
Transmitting file data ..done
Committing transaction...
Committed revision 3.
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ 

Check out the repo as a different user:
=======================================
ilir@ilir-MacBookPro:~$ su - root
Password: 
root@ilir-MacBookPro:~# cd /tmp
root@ilir-MacBookPro:/tmp# mk dir a1
mk: command not found
root@ilir-MacBookPro:/tmp# mk dir a1
mk: command not found
root@ilir-MacBookPro:/tmp# mkdir a1
root@ilir-MacBookPro:/tmp# cd a1
root@ilir-MacBookPro:/tmp/a1# svn --username dema co https://markus.cdf.toronto.edu/svn/csc165-2016-01/c5dema
Authentication realm: <https://markus.cdf.toronto.edu:443> MarkUs Subversion Repository
Password for 'dema': **********


-----------------------------------------------------------------------
ATTENTION!  Your password for authentication realm:

   <https://markus.cdf.toronto.edu:443> MarkUs Subversion Repository

can only be stored to disk unencrypted!  You are advised to configure
your system so that Subversion can store passwords encrypted, if
possible.  See the documentation for details.

You can avoid future appearances of this warning by setting the value
of the 'store-plaintext-passwords' option to either 'yes' or 'no' in
'/root/.subversion/servers'.
-----------------------------------------------------------------------
Store password unencrypted (yes/no)? yes
A    c5dema/Test
A    c5dema/Test/file.txt
A    c5dema/Test/file1.txt
Checked out revision 3.
root@ilir-MacBookPro:/tmp/a1# 

Using the original session, modify something:
=============================================
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ vi file1.txt
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ cat file1.txt
Mickey Mouse
Bugs Bunny
Pikachu
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ svn commit -m "Added Pikachu"Sending        file1.txt
Transmitting file data .done
Committing transaction...
Committed revision 4.
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ svn status
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ cat file.txt
apple
pear
banana

However on the new sessions we are still at the previous version:
=================================================================
root@ilir-MacBookPro:/tmp/a1/c5dema/Test# cat file1.txt
Mickey Mouse
Bugs Bunny

root@ilir-MacBookPro:/tmp/a1/c5dema/Test# 

On the new session, do a svn update:
====================================
root@ilir-MacBookPro:/tmp/a1/c5dema/Test# svn update
Updating '.':
U    file1.txt
Updated to revision 4.
root@ilir-MacBookPro:/tmp/a1/c5dema/Test# cat file1.txt
Mickey Mouse
Bugs Bunny
Pikachu
root@ilir-MacBookPro:/tmp/a1/c5dema/Test# 

Conflicts
=========
Say both sessions do two different modifications.

Old session:
============
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ cat file1.txt
Mickey Mouse
Bugs Bunny
Pikachu
Superman
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ 

New session:
============
root@ilir-MacBookPro:/tmp/a1/c5dema/Test# vi file1.txt
root@ilir-MacBookPro:/tmp/a1/c5dema/Test# cat file1.txt
Mickey Mouse
Bugs Bunny
Pikachu
Spiderman
root@ilir-MacBookPro:/tmp/a1/c5dema/Test# 
root@ilir-MacBookPro:/tmp/a1/c5dema/Test# svn commit -m "Added Spiderman"
Sending        file1.txt
Transmitting file data .done
Committing transaction...
Committed revision 5.
root@ilir-MacBookPro:/tmp/a1/c5dema/Test# 

The commit on the old session fails:
====================================
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$ svn commit -m "Added Superman"
Sending        file1.txt
Transmitting file data .svn: E155011: Commit failed (details follow):
svn: E155011: File '/home/ilir/csc207repos/a1/c5dema/Test/file1.txt' is out of date
svn: E170004: Item '/Test/file1.txt' is out of date
ilir@ilir-MacBookPro:~/csc207repos/a1/c5dema/Test$