What does ADDI capture about a COBOL program's sequential file processing that is useful for modernization?

Think of it like working hands-on with IBM mainframe systems — the answer here is 'The file organization, access mode, and record format defined in each SELECT clause and FD entry'. ADDI captures SELECT clause and FD entry information to understand file organization, access mode, and record format, which informs how file I/O must be replaced by Java I/O or database calls during t. On real mainframe exams, this concept comes up repeatedly so make sure you have it locked in.