Adding hw03
Adding test1.c
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Adding lecture11
Adding hw04
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
Adding hash.c
Merge branch 'master' of https://github.com/AllenDowney/SoftwareSystems
updating