As the Homebrew Computer Club met and MITS frantically shipped Altairs, researchers at Xerox PARC were seemingly a decade or more ahead. They already knew what would make personal computers useful, and researchers were working on an ecosystem to support a typical office task. Writing and printing documents. Gary Starkweather had tested his SLOT laser printer using analog signals, flying-spot scanners, and raw binary test patterns to prove it was capable of high-quality printing. The next hurdle.