You can use #define number 123 or #define string @"abc" inside the .h and any file that imports it should be able to use the preprocessor name you chose. k is a common prefix for these types of macros as they're in fact constant values.
NOTE: The comments show that there is a difference between using preprocessors you define and actual global variables (with extern declared) though both can be used in separate files by importing the .h file where you declared/defined them.
