3.3.3.5 How Do I Place Variables In Program Memory?

The const qualifier implies that the qualified variable is read-only. Since these objects cannot be written, they are typically placed in program memory, thus freeing valuable data RAM. The exceptions to this are const-qualified parameters and some const-qualified auto objects. See 5.1.2.4 Const Auto Objects and 5.4.3 Objects in Program Space for more information. Variables that are qualified const can also be made absolute, so they can be positioned at an address you nominate (see 5.4.4.2 Absolute Objects In Program Memory).