„In computability theory, the halting problem can be stated as follows: Given a description of an arbitrary computer program, decide whether the program finishes running or continues to run forever. This is equivalent to the problem of deciding, given a program and an input, whether the program will eventually halt when run with that input, or will run forever.
Alan Turing proved in 1936 that a general algorithm to solve the halting problem for all possible program-input pairs cannot exist. A key part of the proof was a mathematical definition of a computer and program, what became known as a Turing machine; the halting problem is undecidable over Turing machines. It is one of the first examples of a decision problem.“
A BNF specification is a set of derivation rules, written as
<symbol> ::= __expression__where <symbol> is a nonterminal, and the __expression__ consists of one or more sequences of symbols; more sequences are separated by the vertical bar, '|', indicating a choice, the whole being a possible substitution for the symbol on the left. Symbols that never appear on a left side are terminals. On the other hand, symbols that appear on a left side are non-terminals and are always enclosed between the pair <>.
The ‚::=‘ means that the symbol on the left must be replaced with the expression on the right“
For those who’re to young for an original apple bought in the shop, here is the ultimative chance to get their own one
“ The replica 1 is a functional clone of the apple 1 computer created by Steve Wozniak in 1976. This was the computer that Steve Jobs and Woz used to start Apple Computers in 1976. The latest version of the replica 1 is labeled SE for Second Edition. The replica 1 functions exactly like the apple 1 with many of the same components like a 6502 CPU and 6821 PIA. It comes with 32K RAM and 8K EEPROM. Addtional features like a ps/2 port, serial, USB port, ATX and DC wall power supply connectors makes the replica 1 a fully functional computer system for todays collector or hobby builder. Available as a kit or assembled, the replica 1 is sure to give you hours of fun and excitement as you relive the glory days of computing. As a new feature, a full blown assembler called Krusader written by Ken Wessen was added to the EPROM space giving the user the ability to assembler 6502 programs right on the replica 1 without a PC. Write 6502 machine code programs using mnemonics instead of just programming hex code into the memory. This added programming tool makes the repica 1 not only a nostalgic computer but a great learning tool and introduction to microprocessors.“