Where games and application writers were concerned with the stability and functionality of their software, the demo writer was typically interested in how many CPU cycles a routine would consume and, more generally, how best to squeeze great activity onto the screen.Writers went so far as to exploit known hardware errors to produce effects that the manufacturer of the computer had not intended.
Prior to the popularity of IBM PC compatibles, most home computers of a given line had relatively little variance in their basic hardware, which made their capabilities practically identical.
Therefore, the variations among demos created for one computer line were attributed to programming alone, rather than one computer having better hardware.
This created a competitive environment in which demoscene groups would try to outperform each other in creating outstanding effects, and often to demonstrate why they felt one machine was better than another (for example Commodore 64 or Amiga versus Atari 800 or ST).
Demo writers went to great lengths to get every last bit of performance out of their target machine.
The demoscene is an international computer art subculture that specializes in producing demos: small, self-contained computer programs that produce audio-visual presentations.
The main goal of a demo is to show off programming, artistic, and musical skills.
The demoscene's roots are in the home computer revolution of the late 1970s, and the subsequent advent of software cracking.
Crackers illegally distributed video games, adding introductions of their own making ("cracktros"), and soon started competing for the best presentation.
With many of the past's challenges removed, the focus in making demos has moved from squeezing as much out of the computer as possible to making stylish, beautiful, well-designed real time artwork – a directional shift that many "old school demosceners" seem to disapprove of.
This can be explained by the break introduced by the PC world, where the platform varies and most of the programming work that used to be hand-programmed is now done by the graphics card.
This gives demo-groups a lot more artistic freedom, but can frustrate some of the old-schoolers for lack of a programming challenge. Demo parties have competitions with varying limitations in program size or platform (different series are called compos).