GATE CS 1998 Q1.25 — Runtime Environments

In a resident operating system, the core components required to load and execute user programs must always remain in the main memory.

• Loader: The primary function of a loader is to load programs (executable files) from secondary storage into the main memory for execution. Since any program (including the assembler, linker, or compiler itself) must first be loaded into memory before it can run, the loader must reside in the main memory under all situations.
• Assembler, Linker, and Compiler: These are system software tools used during the program development phase (translation and linking). They are only loaded into memory when needed and can be released once their tasks are complete. They do not need to reside in the main memory permanently.

Therefore, the Loader must always reside in the main memory.