What a linker is
A linker is a program that combines one or more pieces of compiled code, along with any needed libraries, into a single executable program. When source code is compiled, it may be turned into separate object files. The linker takes these pieces and joins them together, resolving the connections between them, to produce a complete program that can actually be run.
Separate compilation
Large programs are often built from multiple source files, each compiled separately into its own object file. This modular approach has benefits, but it means the program exists in pieces that are not yet a runnable whole. The linker's job is to bring these pieces together. By allowing separate compilation followed by linking, the toolchain supports building big programs in manageable parts.
Resolving references
Different pieces of a program often refer to things defined in other pieces, such as a function defined in one file and used in another. These references need to be connected for the program to work. The linker resolves them, matching each use to its definition across the pieces. This resolution is a central part of what the linker does, tying the separate parts into a coherent whole.
Including libraries
Programs frequently rely on libraries, which are collections of reusable code. The linker incorporates the needed parts of these libraries into the final program, so that the functionality they provide is available. This lets programs build on existing code without having to include all of it manually, with the linker handling the job of pulling in what is required.
The linker in the toolchain
The linker typically runs after compilation, as one of the final steps in producing an executable. The compiler turns source into object files, and the linker combines those into the finished program. Understanding the linker clarifies how the separate results of compilation become a single runnable application, completing the build process.
Why it matters
The linker is an important part of how programs are built. Understanding what a linker is - combining compiled pieces and libraries into one executable - clarifies a key step in turning source code into a runnable program. For anyone interested in how software is built, it is a valuable concept to understand.
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See also: What is code generation in compilers? Explained, What is a compiler vs interpreter?.
Sources
Published date reflects the original event date (2026-08-11). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
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