Methods for generating deterministic fractals and image compression -- Optimum simulation of meshes by small hypercubes -- Seven hard problems in symbolic background knowledge acquisition -- Subsequential functions: Characterizations, minimization, examples -- Past proves more invariance properties but not pca's -- Complexity issues in discrete neurocomputing -- Two-way reading on words -- Proofs and reachability problem for ground rewrite systems -- Problems complete for ?L -- Constructive matching — Explanation based methodology for inductive theorem proving -- Characterizing complexity classes by higher type -- The distributed termination problem : Formal solution and correctness based on petri nets -- Greedy compression systems -- A DIV(N) depth Boolean circuit for smooth modular inverse -- Learning by conjugate gradients -- Monoids described by pushdown automata -- Optimal parallel 3-colouring algorithm for rooted trees and its application -- Hierarchies over the context-free languages -- A hierarchy of unary primitive recursive string-functions -- Minimizing picture words -- Remarks on the frequency-coded neural nets complexity -- Picture generation using matrix systems -- Representing heuristic-relevant information for an automated theorem prover -- A new method for proving lower bounds in the model of algebraic decision trees -- Area time squared and area complexity of VLSI computations is strongly unclosed under union and intersection -- Decision procedure for checking validity of PAL formulas.

This volume contains the texts of the tutorial lecture, five invited lectures and twenty short communications contributed for presentation at the Sixth International Meeting of Young Computer Scientists, IMYCS '90. The aim of these meetings is threefold: (1) to inform on newest trends, results, and problems in theoretical computer science and related fields through a tutorial and invited lectures delivered by internationally distinguished speakers, (2) to provide a possibility for beginners in scientific work to present and discuss their results, and (3) to create an adequate opportunity for establishing first professional relations among the participants.