Loader (computing) in the context of ZX81

A dynamic linker is an operating system feature that loads and links dynamic libraries for an executable at runtime; before or while it is running. Although the details vary by operating system, typically, a dynamic linker copies the content of each library from persistent storage to RAM, fills jump tables and relocates pointers.

Linking is often referred to as a process that is performed when the executable is compiled, while a dynamic linker is a special part of an operating system that loads external shared libraries into a running process and then binds those shared libraries dynamically to the running process. This approach is also called dynamic linking or late linking.

Software cracking (known as "breaking" mostly in the 1980s) is an act of removing copy protection from a software. Copy protection can be removed by applying a specific crack. A crack can mean any tool that enables breaking software protection, a stolen product key, or guessed password. Cracking software generally involves circumventing licensing and usage restrictions on commercial software by illegal methods. These methods can include modifying code directly through disassembling and bit editing, sharing stolen product keys, or developing software to generate activation keys. Examples of cracks are: applying a patch or by creating reverse-engineered serial number generators known as keygens, thus bypassing software registration and payments or converting a trial/demo version of the software into fully-functioning software without paying for it. Software cracking contributes to the rise of online piracy where pirated software is distributed to end-users through filesharing sites like BitTorrent, One click hosting (OCH), or via Usenet downloads, or by downloading bundles of the original software with cracks or keygens.

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 types 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.

A linker or link editor is a computer program that combines intermediate software build files such as object and library files into a single executable file such as a program or library. A linker is often part of a toolchain that includes a compiler and/or assembler that generates intermediate files that the linker processes. The linker may be integrated with other toolchain tools such that the user does not interact with the linker directly.

A simpler version that writes its output directly to memory is called the loader, though loading is typically considered a separate process.

The ZX81 is a home computer developed by Sinclair Research and manufactured in Dundee, Scotland, by Timex Corporation. It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and designed to be a low-cost introduction to home computing for the general public. It was hugely successful; more than 1.5 million units were sold. In the United States it was initially sold as the ZX-81 under licence by Timex. Timex later produced its own versions of the ZX81: the Timex Sinclair 1000 and Timex Sinclair 1500. Unauthorized ZX81 clones were produced in several countries.

The ZX81 was designed to be small, simple, and above all, inexpensive. Video output is for a television set rather than a dedicated monitor. It contains only four silicon chips and 1 KB of RAM. It has no power switch or moving parts, excepting a VHF TV channel selector switch in some models. It has a pressure-sensitive membrane keyboard. Programs and data are loaded and saved onto compact audio cassettes. The ZX81's limitations prompted a market in third-party peripherals to improve its capabilities. Its distinctive case and keyboard brought designer Rick Dickinson a Design Council award.