H6: Add table of contents

exercises/h6.md

@@ -6,6 +6,21 @@ Linux servers - Exercice 6
 
 This exercise is a part of [Linux servers (ICT4TN021, spring 2018) // Linux-palvelimet (ICT4TN021, kevät 2018)](http://www.haaga-helia.fi/fi/opinto-opas/opintojaksokuvaukset/ICT4TN021) school course organized as a part of Information Technology studies in Haaga-Helia university of Applied Sciences, Helsinki, Finland. Course lecturer [Tero Karvinen](http://terokarvinen.com/) has defined the original assignment descriptions in Finnish presented in this document in English. Answers and translations have been written by Pekka Helenius (me, ~ Fincer).
 
+*Table of contents:*
+--------------
+
+[a) Write and execute "Hello world" in three code languages of your choice. Set up a necessary development environments.](https://github.com/Fincer/linux_server_setup/blob/master/exercises/h6.md#a-write-and-execute-hello-world-in-three-code-languages-of-your-choice-set-up-a-necessary-development-environments)
+
+    - [Perl (hello.pl)](https://github.com/Fincer/linux_server_setup/blob/master/exercises/h6.md#perl-hellopl)
+
+    - [Python 3 (hello.py)](https://github.com/Fincer/linux_server_setup/blob/master/exercises/h6.md#python-3-hellopy)
+
+    - [C (hello.c)](https://github.com/Fincer/linux_server_setup/blob/master/exercises/h6.md#c-helloc)
+
+- [b) (optional) Write a simple program for some practical purpose with each language. Ideas: utilize the key benefits of your language of choice. Take an input value from a user, generate a calculation and print the output (input-processing-layout).](https://github.com/Fincer/linux_server_setup/blob/master/exercises/h6.md#b-optional-write-a-simple-program-for-some-practical-purpose-with-each-language-ideas-utilize-the-key-benefits-of-your-language-of-choice-take-an-input-value-from-a-user-generate-a-calculation-and-print-the-output-input-processing-layout)
+
+--------------
+
 **a)** Write and execute "Hello world" in three code languages of your choice. Set up a necessary development environments.
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