Resident Systems in Main Memory in a Resident OS Computer

In a resident operating system (OS) computer, there are several system components that need to reside in the main memory at all times. Among these components, the loader is the system that must reside in the main memory under all situations.

The Role of the Loader

The loader is responsible for loading executable programs into the main memory so that they can be executed by the processor. It performs the following tasks:

1. Allocation of Memory: The loader allocates memory space in the main memory to load the executable program. It determines the appropriate memory locations for different parts of the program, such as the code segment, data segment, and stack.

2. Address Resolution: The loader resolves the symbolic addresses used in the program to their corresponding physical addresses in the main memory. It replaces symbolic references with actual memory addresses so that the program can be executed without any issues.

3. Relocation: The loader performs relocation of the program by adjusting the program's memory addresses to match the actual memory locations where the program is loaded. This is necessary because the program may have been compiled and linked at a different memory location.

4. Linking: The loader may also perform linking tasks by resolving external references and combining multiple object files into a single executable program. This ensures that all the required modules and libraries are properly linked together.

5. Loading: Finally, the loader loads the program into the allocated memory space in the main memory. It copies the instructions and data from the executable file into the appropriate memory locations.

The Significance of the Loader

The loader plays a crucial role in the execution of programs in a resident OS computer. Without the loader residing in the main memory, the operating system would not be able to properly allocate memory, resolve addresses, perform relocation, and load programs for execution. Therefore, the loader must always be present in the main memory to ensure the successful execution of programs in a resident OS computer.

Conclusion

In a resident OS computer, the loader is the system component that must reside in the main memory under all situations. It performs essential tasks such as memory allocation, address resolution, relocation, linking, and loading of executable programs. Without the loader, the operating system would not be able to properly load and execute programs, making it a critical component in the resident OS environment.