Added isbn.
Added first programme, invokes the exit system call with a status code.
Added object files and Vim swap files to the gitignore.
Added maximum programme. It returns the largest number in a list.
Added minimum. MOdified maximum that returns the smallest number in a list.
Added maximum variation that uses 255 as the list terminator.
Modified maximum to to use a memory address to mark the end of the list.
Modified maximum to use the length of the list instead of a terminating value.