Exercise 14: Writing and Using Functions

Contains extra credit of writing own functions and playing with
string.h library functions isalpha, isdigit, isupper and islower.

Lesson learnt: argv[i][j] gives you character code and not position
mark in a loop! In a nested loop, think i as hour
hand and j as minute hand, i can move only after j has finished its
iteration. So the marker that seeing most work is j. j ticks slowly
towards the end of each unit and hence you should compare the length
of a unit against value as seen by j.