DJL Software (for "Dave J and John LookerSoftware") was is mainly known as the co-author of the [[Speedlock|Speedlock]] protection system, used on many cassette games released in the UK. Speedlock was a modified version of the [[Spectrum]]'s cassette routines with protection added.
As the A fast loader and protection system continued to evolveused on many cassette games, programs such as [[Soft-Lok]] and the [[Bonzo]] suite were upgraded to break the as a protectionon disc games.
A separate disc protection system, DJL was also the author of several Amstrad games including [[8k Speedlock3d Stunt Rider]], relied on the fact that the CPCand [[Nigel Mansell's hardware could reliably read but not write 8k sectors. To get around thisGrand Prix]], the in addition to self-published titles such as [[Executionerhttps://www.retrogames.co.uk/041976/Sinclair/Frogger-by-DJL-Software Frogger]]'s utility . [[XexorCategory:CPC scene members]] included a 'brain file' solution to crack individual games before copying them.