Code Notes – F-15 Strike Eagle

It was during the 1984 to 1985 period that the author so desperately fixates on that what’s known as the demo scene began to form, starting within the cracking scene but soon becoming an at least partially seperated entity. To begin with, the crackers would alter games to insert their pseudonyms somewhere within the text but it didn’t take long for the first crack screens and intros[1] to appear which announced who had broken the game’s protection, greeted their friends and ragged on enemies or promoted affiliated bulletin boards. Lone crackers also began to band together into groups with names like Crackman Crew, Piracy Zone Software or the Terrestrial Breakin’ Company. Which brings us quite neatly to…

 

F-15 Strike Eagle by Black Bag

An Apple II crack intro released in 1985
(No on-screen credits for the intro available)

The bitmapped picture, shown below appears to have been ripped from Microprose’s game F-15 Strike Eagle – a cracked version of which this intro originally preceded – but the author has previously whined about “borrowed” assets so we’ll move on quickly; pressing a key continues to the part we’re actually concerned with as regards the Code Notes series.

F-15 Strike Eagle (Apple II)

The intro is targeted at standard Apple II systems which offer six possible colours on screen (with some caveats on actual use) but no colour registers, so the routine for the moving bars essentially selects a colour value and writes it to a row of the display RAM[2]. Similarly, the “Black Bag Presents” logo needs to be constantly cleared and rewritten to the screen in order to make it bounce vertically between the two colour bars, which is harder than it might sound considering the non-contiguous nature of the bitmap in memory! There isn’t any music being played whilst this is going on, so instead the Apple II’s speaker is being made to click at a regular rate to generate a noise which your correspondent would describe as similar to an idling engine.

F-15 Strike Eagle (Apple II)

From a C64CD perspective, the overall look of Apple II and C64 crack intros from 1984 are quite similar – usually either static text or a bitmap, occasionally sporting a simple colour effect – but by 1985 when F-15 Strike Eagle was released the bar had been raised some distance by the more elaborate production numbers on the C64 from people like 1001 Crew and Crackman or indeed early demos from the Norwegian Crackware Company, International Cracking Group and others which have music, effects and scrolling messages. That doesn’t make F-15 Strike Eagle a bad intro of course, but it does highlight how much harder the Apple II is to learn compared to the C64, despite the author’s previous claims to the contrary.

Finally, as an aside your correspondent heartily recommends watching Jason Scott’s excellent Defcon talk from 2010 about his love for crack screens (the precursors to crack intros) because it covers that early part of the Apple II cracking scene and the inter-group wars with great relish; the “anti-greeting” your correspondent has been including to the author in C64CD releases is a more polite version of that!

[1] The portmanteau “cracktro” was coined long after the first crack intros appeared and your correspondent prefers to use the original, more descriptive term.

[2] This description oversimplifies things somewhat; the Apple II only uses seven of the eight available bits in a byte for actual bitmap data (with the most significant bit of each byte selecting the colour set) so it isn’t merely doing one LDA and a series of STA commands; there will be two values in play, one written to the odd bytes across a line and the other to the even.

 

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