Loader

Loader is a system program that sets up an executable program in main memory ready for execution. It is responsible for loading the executable program into memory, resolving any unresolved symbols, and preparing the program for execution.

Process of Loading

The loading process involves several steps:

1. Loading the executable file: The loader reads the executable file from the storage device into main memory. The executable file contains the compiled code and data that make up the program.

2. Memory allocation: The loader allocates memory space for the program in main memory. It determines the size of the program and finds a suitable location in memory to store it.

3. Relocation: The loader performs the relocation process to adjust the program's memory addresses. This is necessary because the program may have been compiled to run at a different memory location than where it is being loaded.

4. Symbol resolution: If the program contains any unresolved symbols, the loader resolves them by linking them to the appropriate memory addresses. Symbols are references to memory locations or data that are defined elsewhere in the program or in external libraries.

5. Initialization: The loader initializes any necessary data structures and resources required for the program to run. This may include setting up the stack, initializing global variables, and performing any other necessary initialization tasks.

6. Control transfer: Once the loading process is complete, the loader transfers control to the starting point of the program. The program is now ready for execution.

Importance of Loader

The loader plays a crucial role in the execution of programs. It is responsible for properly setting up the program in memory, resolving any dependencies, and preparing the program for execution. Without a loader, the program would not be able to run as it would not be properly loaded into memory and its symbols would remain unresolved.

Conclusion

In summary, the loader is a system program that sets up an executable program in main memory ready for execution. It performs tasks such as loading the executable file, allocating memory, relocating addresses, resolving symbols, initializing resources, and transferring control to the program. It is an essential component of the execution process and ensures that the program can run successfully.