I have to say, for me 10 years is an extremely long time: back when this site launched, had you asked me what tells a computer what to do, my answer would have been along the lines of "fairies and pixie dust", because I was six years old back then and I didn't have an account on Scratch until November.

Let it never be said that that is the wrong answer.

Pixiedust, a new esolang (esoteric programming language) by me

This language uses the characters *+.. Any other non-whitespace characters will result in a syntax error. This is an assembly language with instructions separated by newlines.

Instructions

• * O R X Y is a mathematical operation:
  • O specifies the operation to use: . for copy, ++ for addition, +. for subtraction, ** for multiplication, *. for division, *+ for modulo. +* is reserved for future use.
  • R specifies the register to store the result to. Registers hold single 32-bit integers. Each register is two characters, with a few special registers: ** is the memory pointer, *. is the value at the pointer, *+ reads a byte from STDIN or writes to STDERR, .. is the test register, and .* is the numeric literal portal.
  • X and Y are expressions. More on these below. For a copy operation, Y should be omitted.
• . C X Y performs the comparison specified by C and stores it with 0/1 in the .. register. =<> are indicated by *+., respectively. X and Y are expressions.
• ++ X prints the Unicode character represented by expression X to STDOUT.
• +. L defines a program label; L can be any number of characters.
• +* T L jumps to label L based on the condition T. T can be * to jump if .. is not 0, . to jump if ..is 0, or + to jump regardless of the value in ...

Expressions can be either a normal register, or the reserved .* register followed by a number literal. A number literal is up to 32 + or . characters terminated with a *. With + meaning 1 and . meaning 0, they should form the binary representation of the number exactly how it would be stored as an int in a Java stack frame. Leading . characters can be omitted, and the terminating * can be left out if it's at the end of a line.

A golfed Hello World program would look like this:

++.*+..+...++.*++..+.+++.*++.++..++.*++.++..++.*++.++++++.*+.++..++.*+.....++.*+.+.+++++.*++.++++++.*+++..+.++.*++.++..++.*++..+..++.*+....+

But that's boring, and it doesn't even look too much like pixie dust! So I wrote some code to rewrite it to the following, equivalent program:

++               .   *+       ..  +.        ..            .                  .              .          .++   .*    ++.    .    +           .+                         *++.        *   ++  .  ++     .  .    *                         .              .      .   .       .*++.     *  ++ .++ .   .*                         .                 .   .    . ..++      .  *     ++.    ++++  *                 .      .   ..          .              .*++   .* + .   ++.              .  .                  .           .   .   .                .++  .*+           .   .. .     .*                                 .  .  . ..         . .   .*++.  *      +. +      .        +++*++. *++       .  ++++             ..                                 .     ..++.        * +++ ..   +  .*                         .++        . *            ++        . ++       ..*            .                          ..++  .  *  ++.                  .+.. .          .    .                    . ...        ..++   .  *+                ..    . .    +*.         .      .       .         .       .*