What is the role of a linker in programming languages?

A linker in programming languages combines various code and data sections into a single executable file.

In more detail, a linker, also known as a link editor, plays a crucial role in the process of creating executable programs. It is a program that takes one or more object files generated by a compiler and combines them into a single executable program. The main purpose of a linker is to resolve references between these object files into definite addresses.

When a program is divided into multiple source files, each file is compiled separately. This results in multiple object files, each containing a section of the program's code or data. However, these object files are not yet ready to be executed because they contain unresolved references, or 'links', to other parts of the program. For example, one object file might contain a function that is called by code in another object file. The linker's job is to resolve these links by replacing each reference with the correct address.

The linker also combines the separate code and data sections from each object file into a single, contiguous block of memory. This is necessary because the computer's processor needs to be able to access the entire program's code and data in a single, continuous block of memory in order to execute the program.

In addition to resolving references and combining sections, the linker also performs other tasks such as allocating memory for static variables, arranging for the initialisation of dynamic variables, and setting up the program's entry point (the location in the code where execution begins).

In summary, the linker is a vital part of the programming process, turning the separate pieces of code and data produced by the compiler into a single, executable program. Without the linker, the individual object files produced by the compiler would be unable to interact with each other, and the program would not be able to run.