What is the role of a linker loader?

A linker loader is responsible for linking and loading program modules into memory for execution.

In more detail, a linker loader plays a crucial role in the process of program execution. It is a system program that combines one or more separate object program modules into a single, executable program. The linker loader performs two main functions: linking and loading.

Linking is the process of combining various pieces of code and data together to form a single executable that can be loaded into memory. During the linking process, the linker loader resolves symbolic references between object modules, connects all the modules of a program together and also links any required library routines. This results in a complete program that can be executed by the system.

Loading, on the other hand, is the process of placing the executable into memory. The loader allocates memory for the program, relocates its code and data as necessary and starts the program's execution. This involves copying the blocks of code and data from the executable file into specific locations in memory. Once the program is loaded into memory, it can be started by the operating system.

The linker loader also handles the relocation of code, which involves adjusting absolute references between the different modules of a program. This is necessary because each module is compiled and assembled independently, and the exact location in memory where it will be loaded is not known at compile time. The linker loader adjusts these references so that they point to the correct locations in memory.

In summary, the linker loader is a vital component in the process of turning source code into a running program. It links together separate modules, resolves symbolic references, loads the program into memory, and adjusts references between modules. Without the linker loader, it would not be possible to run complex programs that are made up of multiple modules.