How to create my own mode?

[Jeckob]

Hi, i have written some functions in elisp to get some strings
formated. Now i want to have that only active when i open *.ci
files....how can i do this in elisp?  Here is my code:

(defun pre-process-words (words)
  (loop
     with result = '()
     while words
     do (if (string= ":" (first words))
            (progn
              (push (format "%s %s" (first words) (second words))
result)
              (setf words (cddr words)))
            (progn
              (push (first words) result)
              (setf words (cdr words))))
     finally (return (nreverse result))))

(defun format/align-and-newline ()
  (interactive)
  (let* ((anker (point))
         (start (progn (beginning-of-line) (point)))
         (end   (progn (end-of-line) (point)))
         (line  (buffer-substring start end))
         (words (pre-process-words (split-string line))))
    (setq testpoint (first words))
    (setq doppeltab 57)
    (setq tabFlag 0)
    (setq merker1 0)
    (setq kreuzFlag 0)
    (setq doppelFlag 0)
    (when (position ?+ (first words))
      (progn
        (setq kreuzFlag 1)
        (previous-line 1)
        (beginning-of-line)
        (setq start (point))
        (end-of-line)
        (setq end (point))
        (setq line (buffer-substring start end))
        (next-line 1)
        (beginning-of-line)
        (when (or (position ?: line) (position ?+ line) )
          (progn
            (setq doppelFlag 1)
            (setq start (point))
            (end-of-line)
            (setq end (point))
            (setq line (buffer-substring start end))
            (setq words (split-string line))
            (beginning-of-line)
            (forward-char 1)
            (setq start (point))
            (delete-region start end)
            (move-to-column 59 t)
            (insert (format "%-17s" (second words)))
            (insert "\n")
            ))
        (when (= doppelFlag 0)
          (progn
            (end-of-line)
            (insert "\n")
            ))))
    (when (= kreuzFlag 0)
      (progn
        (if (setq posDoppel (position ?: line) )
            (if (position ?. testpoint)
                (insert "\n")
              (delete-region start end)
              (insert (format "%-10s" (first words)))
              (setq wortLaenge (length (first words)))
              (when (> wortLaenge 9)
                (progn
                  (insert " ")
                  ))
              (dolist (word (cdr words))
                (if (position ?: word)
                    (progn
                      (if (= tabFlag 0)
                          (progn
                            (when (> merker1 doppeltab)
                              (progn
                                (setq doppeltab merker1)
                                ))
                            (move-to-column doppeltab t)
                            (insert (format "%-17s" word))
                            (setq wortLaenge (length word))
                            (when (> wortLaenge 16)
                              (progn
                                (insert " ")
                                ))
                            (setq tabFlag 1)
                            )
                        (progn
                          (insert (format "%-17s" word))
                          (setq wortLaenge (length word))
                          (when (> wortLaenge 16)
                            (progn
                              (insert " ")
                              ))
                          )))
                  (progn
                    (insert (format "%-10s" word))
                    (setq wortLaenge (length word))
                    (when (> wortLaenge 9)
                      (progn
                        (insert " ")
                        ))
                    (setq merker1 (current-column))
                    )))
              (if (beginning-of-line)
                  (insert "\n")
                (setq anker (point)))
              ))
        (goto-char anker)
        (when (= tabFlag 1)
          (progn 
            (end-of-line)
            ))
        (insert "\n")
        )))) 

Thanks