The Psychology-of-the-Programmer

Programming is making things happen in the future.  What you probably
thought of was "Computer Programmer", when you read the title of this
essay, but I could be wrong.  As Abelson so clearly stated in the
Foreward to Structure and Interpretation of Computer Programs (SICP),
"Educators, generals, dieticians, psychologists, and parents
program. Armies, students, and some societies are programmed."[1]

A Computer Program is something that is held and then executaed
sometime in the future.  The programs that the above stated by Abelson
execute create the worlds we live in.  You create the program you want
to happen, and then execute the program when you want it's results to
occure.  Thus, programming, Computer or otherwise, is making things
happen in the future.

The only constant is the change in Time. It is always progressing,
getting bigger.  The rate of Time is variable, at least according to
the observer.  This gives a rate of change of Time, the only constant
in our world.

(defconstant *dt* 1)

Time is a variable, that is seeded aty it's epoch by
get-universal-time, and thus given an integer value.

(defconstant *epoch* (get-universal-time))

(defvar *t* *epoch*)

(defvar *input*)

(defun get-input ()
       (fresh-line)
       (princ "$ ")
       (setf *input* (read-line)))

(defvar *world*
	(list :world))

(defun update-time ()
       (incf *t* *dt*))

(defun update-world ()
       (update-time)
       (push *world* (cons *t* *input*))
)

(defvar render-world ()
  (print *world*))

;; Let's make a game that never ends aka a simulation.
(loop
	(get-input)
	(update-world)
	(render-world))
==

[1] 
Title: Structure and Interpretation of Computer Programs
Author: Harold Abelson
Author: Gerald J. Sussman
Author: Julie Sussman
Year: 1985
Publisher: The MIT Press
Reference: https://mitpress.mit.edu/sites/default/files/sicp/full-text/book/book-Z-H-5.html#%_chap_Temp_2