Software cracking (known as "breaking" mostly in the 1980s) is the modification of software to remove or disable features which are considered undesirable by the person cracking the software (software cracker), especially copy protection features (including protection against the manipulation of software, serial number, hardware key, date checks and disc check) or software annoyances like nag screens and adware.
A crack refers to the means of achieving, for example a stolen serial number or a tool that performs that act of cracking. Some of these tools are called keygen, patch, loader, or no-disc crack. A keygen is a handmade product serial number generator that often offers the ability to generate working serial numbers in your own name. A patch is a small computer program that modifies the machine code of another program. This has the advantage for a cracker to not include a large executable in a release when only a few bytes are changed. A loader modifies the startup flow of a program and does not remove the protection but circumvents it. A well-known example of a loader is a trainer used to cheat in games. Fairlight pointed out in one of their .nfo files that these type of cracks are not allowed for warez scene game releases. A nukewar has shown that the protection may not kick in at any point for it to be a valid crack.
On the Commodore 64, several methods were used to protect software. For software distributed on ROM cartridges, subroutines were included which attempted to write over the program code. If the software was on ROM, nothing would happen, but if the software had been moved to RAM, the software would be disabled. Because of the operation of Commodore floppy drives, one write protection scheme would cause the floppy drive head to bang against the end of its rail, which could cause the drive head to become misaligned. In some cases, cracked versions of software were desirable to avoid this result. A misaligned drive head was rare usually fixing itself by smashing against the rail stops. Another brutal protection scheme was grinding from track 1 to 40 and back a few times. 2b1af7f3a8