3.3.3.3 How Do I Place Variables in Program Memory?

The const qualifier implies that the qualified object is read only. An object qualified with const might also be placed in program memory, but its exact location will depend on the use of options such as -fdata-sections, and -mpure-code, any linker-script customizations, and whether the variable is initialized. To ensure that objects are placed in program memory, use the space(prog) attribute in addition to the const qualifer.