In modular programming, a linker is essential for combining distinct program modules into a single executable program.

A linker is a system program that plays a vital role in the modular programming paradigm. It takes one or more object files generated by compilers and merges them into a unified executable program through a process known as linking. During this process, the linker resolves references to undefined symbols, assigns absolute addresses to relocatable symbols, and modifies the target code to reflect these addresses.

Modular programming is a software design technique that emphasizes the separation of a program’s functionality into independent, interchangeable modules. Each module acts as a standalone unit of software that can be developed and tested independently. This approach enhances code maintainability and reusability, as individual modules can be debugged separately or utilized across different programs.

The linker is activated when these separate modules must be integrated into a single executable program. It effectively stitches together the object code from each module while resolving any inter-module references. For example, if one module invokes a function defined in another module, the linker ensures that the call correctly reaches the intended function during program execution.

Additionally, the linker is responsible for assigning memory addresses to each module. During the compilation phase, each module is typically compiled in isolation, with the compiler starting the addressing at zero for each module. The linker then adjusts these relative addresses to absolute addresses in the final program memory space.

In summary, the linker is a crucial component of modular programming. It facilitates the advantages of modular programming by enabling the combination of separate modules into a single executable program, resolving references between modules, and assigning absolute memory addresses. Without the linker, the modular programming approach would be impractical, as it would not be possible to assemble the separate modules into a runnable program.