Ada is an advanced language that makes use of a with keyword (an equivalent to the import keyword in Java.) To implement the with keyword, the compiler searches for a file using the same name as the name specified in the with declaration. So for example, if you use
The compiler expects to find a file named aada_compiler_ucs4_character.ads (specification and declaration header file.)
This means the package definition or main procedure (i.e. program) must match the name of the file.1
So to fix this problem, edit your file and compare the name of the package or procedure (program) with the name of the file used to save your code and fix one or the other or both as you see fit.