Well done. I agree with the credits to DJ Delorie (and to Stallman, for the original GCC!). The code of the O.P. is actually not so bad for a teenager; however

Well done. I agree with the credits to DJ Delorie (and to Stallman, for the original GCC!). The code of the O.P. is actually not so bad for a teenager; however, the variables in Spanish do not help: "[isq]" and "[der]" probably stood for "isqierda" and "derecha", so the index of the left and right subtree of an expression. Speaking of Transputers, Dr. Tim King, founder of Perihelion, was another big name of the Transputer times; he sadly passed away last month (he also wrote Tripos, which turned into AmigaDOS).