A pragma is a suggestion to the compiler and can be ignored by any implementation according to the definition of Ada. Refer to appendix B of the LRM for the definition of the predefined pragmas LIST and PAGE . Since these may not be available with any particular compiler, their use should be discouraged in order to attain a high degree of program portability. There should not be anything too difficult for you to understand in these definitions. There is no standard on floating point input.
Some compilers require a decimal point with at least one digit before and after the decimal point.
Experiment and determine the characteristics of your compiler.