Home   LARC   News

My First Programs

Image

This page describes my first experience with programming in 1975-1976 while in the 11th and 12th grades at Beenleigh State High School in Queensland, Australia.

The CompuCorp 325

image

My first exposure to programming came in 11th grade in 1975, when I was 15 or 16 years old. Beenleigh High had purchased a CompuCorp 325, a programmable calculator that was programmed in assembly language via the keyboard. Output was in the form of an 18-character red LED and a tiny 18-character drum printer that printed in black and red. It wasn't intended for use by students, but I managed to get permission to teach myself how to program it.

image

image

My first programs were, of course, games.

Projectile

image

One of my first programs was a projectile game in which the player is given a random target distance $s$ and has to enter the barrel angle $\theta$ for a cannon with fixed muzzle speed $v$ (see the diagram above), and must hit the target with three shots. Since the player is not told the muzzle speed, which changes randomly with each target, they must experiment and estimate the correct angle based on the distance that they missed by.

image image

Coding up this game requires simple quadratic equations that even an 11th grader should know. Let $v_y = v \sin \theta$ be the magnitude of the vertical component of the muzzle velocity (see the diagram at left). If the projectile is fired upwards with muzzle velocity $v_y$, it reaches its highest point (see the diagram at right) when $v_y - gt = 0$ where $g = 9.8 \mbox{m/sec/sec}$, that is, when $t = v_y/g = v \sin \theta/g$. Therefore, the projectile's time in flight is $2t = 2 v \sin \theta/g$ seconds.

The projectile travels a horizontal distance of $h = 2v_x t = 2 v^2 \cos \theta \sin \theta/9.8$ meters. If $h$ is close enough to $s$, then it's a hit. Otherwise, tell the player that they've missed by $h - s$ meters.

Nim

Another of my first programs was a variant of the game of Nim. There are many variants of this game (see, for example, Wikipedia), but I can't remember exactly which one it was. I remember learning the winning strategy from a book that was in the Beenleigh public library in 1975, but again I can't remember exactly which book that was either.

FORTRAN IV

At the end of 11th grade I attended a summer programming camp at the University of Queensland. This was some time between December 1975 and February 1976 (southern hemisphere, remember). There I learned to program in FORTRAN IV using flowcharts. I didn't actually come anywhere near a computer. Instead, we programmed on coding forms that looked something like these:

image

Our program forms were typed up on punch cards overnight by "professional" data entry personnel whose primary purpose seemed to be the adding of random compile time errors to each card deck. The card decks were submitted to the university's DEC PDP KA-10 overnight and the output was delivered to us the next morning. This didn't work very well because it meant that we could only compile once per day, and the data entry staff were apparently a group of chimpanzees wearing boxing gloves.

The hardest thing we had to program was computing binomial coefficients. FORTRAN IV doesn't have recursion, so it wasn't a trivial problem for a 16 year old. I didn't know about Pascal's triangle at the time, either. Remember, the internet didn't exist then, so we couldn't just look things up. I remember that my solution was hopelessly Byzantine but I never got to see whether it worked or not because of the chimpanzees in boxing gloves thing. I'm pretty safe in guessing that it failed miserably.

Created August 3, 2015. Written in HTML 4.01 and CSS 3 using Notepad++. Last updated August 20, 2015.

Valid HTML 4.01 Strict Valid CSS!