What are the main tasks of a linker in code execution?

The main tasks of a linker in code execution are resolving symbol references and combining separate code files into a single executable.

A linker, also known as a link editor, plays a crucial role in the process of program compilation and execution. It is a computer program that takes one or more object files generated by a compiler and combines them into a single executable program. The primary tasks of a linker are to resolve symbol references and to combine separate code files.

Resolving symbol references is one of the key tasks of a linker. In programming, symbols are essentially names given to variables, functions, and other identifiers. During the compilation process, the compiler replaces these symbols with memory addresses. However, not all symbols can be resolved during compilation, especially when they are defined in different source files or libraries. This is where the linker comes in. It scans the object files to find unresolved symbols and replaces them with correct addresses. This process is known as symbol resolution.

The second main task of a linker is to combine separate code files. When a program is split into multiple source files, each file is compiled into a separate object file. The linker takes these object files and combines them into a single executable file. This process is known as file linking. The linker also ensures that the code in one file can correctly access the code in another file. This is particularly important in large projects where code is often split across multiple files for better organisation and maintainability.

In addition to these tasks, the linker also performs other functions such as memory allocation and relocation. It determines the memory locations for the static data and code of the program. It also adjusts the code and data in the program to reflect these memory locations. This process is known as relocation.

In summary, the linker plays a vital role in the process of program execution. It resolves symbol references, combines separate code files, and performs memory allocation and relocation. Without the linker, the separate pieces of code generated by the compiler would not be able to work together as a single, executable program.