remove binaries and IDE files; rename files properly - #68

Fixed some code:
-correct returns for every function
-implicit declaration of parameters
-removed unused variables

to compile everything in one go with bash and gcc:
for d in program*; do echo "$d"; cd "$d"; gcc -Wall program.c -lm; cd ..;done

remove all a.out: files:
find . -type f -name 'a.out' -exec rm {} +

@dk5ee I would love to see you contributing more to the open-source community ❤️