'const' is used to tell the compiler that the variable is initialized one time and never changed. Some computers have the ability to disable writing to a range of memory, and the compiler, linker, and the OS could work together so that 'const' variables end up in a range of memory with writes disabled.
One clever implementation of a loader was an old Monrobot mini-computer. It used a spool with nodes to toggle switchs, similar to a music box to toggle in the initial load program.
Another "clever" trick used on an old mini-computers operating system I worked on was to add the ability to read commands from a tape drive, one of which could load a program from the tape drive, so we could create a "batch" file that consisted of a combination of commands and programs on a tape. Later on another system, we monitored the sequence of programs loaded during OS boot up, and added the ability to boot from tape from the computers BIOS. This was back in the 1970's and 1980's long before boot from cd-rom became a standard for PC's.