add exercises

Author: Kristian Rother

README.md

@@ -51,6 +51,10 @@ Below you find development tools and techniques that help you to write programs
 * [How to recognize good scientific software?](good_software.md)
 * [Citable Code](citable_code.md)
 
+### Extras
+
+* [Exercises](exercises.md)
+
 ----
 
 ## Contact

exercises.md

@@ -0,0 +1,49 @@
+
+# Exercises
+
+### Exercise 1: Track changes
+
+To track changes to their code over time, a programmer copies the entire source folder whenever they finish a piece of work.
+They rename the copy folder so that it contains the current date and copy it to their Google Drive.
+
+**Questions:**
+
+-  What are disadvantages of this approach?
+-  When would it definitely fail?
+-  What is a better alternative?
+
+----
+
+### Exercise 2: Debugging
+
+A programmer debugs a program by reading the code over and over whenever an error occurs.
+This takes a lot of time and sometimes they don't find the bug at all.
+
+**Enumerate as many alternative debugging strategies as possible**
+
+----
+
+### Exercise 3: Testing
+
+A programmer is using a small data file to test their code.
+After changing the code, they run the entire program with the test file and inspect the output carefully.
+They are generally happy with their approach, and it helps them to remove lots of issues.
+
+**Questions:**
+
+- What kind of bugs would you find by testing the program this way?
+- What limitations does the approach have?
+- What is a complementary strategy to make sure the program is working?
+
+----
+
+### Exercise 4: Versions
+
+Two programmers work together on the same program. Both of them use slightly different Python versions.
+After some time, they decide to install exactly the same Python version.
+
+**Questions:**
+
+- What do Python versions differ in? Find one example.
+- How could the programmers install exactly the same versions of Python libraries?
+- One of the programmers is working on another project that requires different library versions. Do they need to get another computer?