A86 (software)

A86 is a compact commercial assembler developed for the Intel x86 family of microprocessors by Eric Isaacson and initially sold as shareware in the 1980s. The assembler can directly produce an MS-DOS compatible .COM file, or an object file for use with a standard linker. A86 uses a slightly simpler syntax for source code and does not require the extensive use of directives as do contemporaries such as the Microsoft Macro Assembler. Isaacson claims that A86 can assemble 100,000 lines of source per second on a Pentium II or better. It comes with a debugger, D86.

A86/D86 target 16-bit x86 platforms. Isaacson added 32-bit support in the mid 1990s in the form of A386 and D386.

Isaacson never ported the A86 family of products to Windows, though it is possible to use the object files created by A386 with a Windows linker. The assembler cannot be used to create 64-bit code.

Code fingerprint

The assembler automatically embeds a "fingerprint" into the generated code through a particular choice of functionally equivalent instruction encodings. This makes it is possible to tell if code was assembled with A86, and also to distinguish between registered and unregistered versions of the assembler, although access to the source code is required.

Dutch Defence

The Dutch Defence is a chess opening characterised by the moves:

History

Elias Stein (1748–1812), an Alsatian who settled in The Hague, recommended the defence as the best reply to 1.d4 in his 1789 book Nouvel essai sur le jeu des échecs, avec des réflexions militaires relatives à ce jeu.

Siegbert Tarrasch rejected the opening as unsound in his 1931 work The Game of Chess, arguing that White should reply with the Staunton Gambit, with White being better after 2.e4 fxe4 3.Nc3 Nf6 4.Bg5 c6 5.f3! exf3.

Theory

Black's 1... f5 stakes a serious claim to the e4 square and looks towards an attack on White's kingside in the middlegame. However, it weakens Black's own kingside somewhat, and does nothing to contribute to Black's development. The Dutch is rare in top-level play. It has never been one of the main lines against 1.d4, though in the past a number of top players, including Alexander Alekhine, Bent Larsen, Paul Morphy and Miguel Najdorf, have used it with success. Perhaps its high-water mark occurred in 1951, when both world champion Mikhail Botvinnik and his challenger, David Bronstein, played it in their World Championship match in 1951. Among the world's current top 10 players, its only consistent practitioner is Hikaru Nakamura.