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A PC booter, or booter, is a type of software for home computer era (early 1980s to early 1990s) personal computers that was loaded and executed in the bootup of the computer, from a bootable floppy disk, rather than as a regular program; a booter thus bypassed any operating system that might be installed on the hard disk of the computer. Video games were the type of application most commonly distributed as booters.
Amiga games and those for other computers were often distributed as bootable floppies using a custom boot block which would consist of a custom loader. These disks contained no filesystem; instead, the custom loader would read the tracks directly. Many Amiga games were released as such in order to thwart piracy, and to utilize the RAM otherwise occupied by the AmigaOS. In early to mid-1990s, disks with a custom boot block became very popular for making so-called "trackmos" by demo groups.
An example computer system where this technique was not used is the Commodore 64, since it was not designed to read any boot block from external storage media prior to starting operating system routines and entering the BASIC interpreter. However, there were cartridges that mapped their program code directly into the Commodore 64's addressable memory (no loading required) and which would start immediately, though these are not considered booters due to no loading taking place.
While booters provided a safe form of copy protection, programs such as Locksmith and Copy II PC existed that provided a method for copying of these disks; these were known as bit nibblers.
Today, IBM PC compatible computers can still boot from floppies, CD-ROMs/DVDs, USB storage devices etc., if a corresponding drive is connected to the system. However, it may require to change boot device priority in the BIOS setup utility.
- Ease of use (the software would start automatically, without any further action required by the user).
- Insulation (few chances to manually alter program files). In a way, the booter acted as a sandbox, even though the concept didn't exist yet.[weasel words]
- Copy prevention (the booter floppies can be hard to read and copy with a regular operating system – mostly because they often used a nonstandard filesystem or formatting).
- Bypassing the normal operating system (to use some specialized replacement).
The last benefit was critical for games, as it allowed to use specialized replacements such as lightweight filesystems and memory access. This allowed performance boosts, especially for graphical applications.
- The application cannot co-exist with other installed applications (because of the insulation described in the previous section).
- Bypassing the normal operating system forced the developers to anticipate every hardware-related or driver-related issue. They would have to write drivers themselves. This could cause compatibility issues on unusual equipment.