From a conversion standpoint, the only language difference between VS COBOL II, Release 4 and Enterprise COBOL is the addition of new reserved words. A complete list of reserved words, including those reserved for object-oriented COBOL is included in COBOL reserved word comparison.
If upgrading from VS COBOL II, Release 3, there are also three minor language differences due to ANSI interpretation changes. Aside from these small differences, you can compile with Enterprise COBOL without change and receive the same results. For details, see Upgrading VS COBOL II source programs.
VS COBOL II Release 2 programs are coded to the COBOL 74 Standard as are VS COBOL II programs compiled with the CMPR2 compiler option. The CMPR2 compiler option is no longer supported by Enterprise COBOL, requiring source conversion for all VS COBOL II Release 1 or 2 programs as well as any VS COBOL II Release 3 or 4 programs that were compiled with CMPR2. Conversion tools can help you upgrade your source programs to the COBOL 85 Standard. Details of language differences between CMPR2 and NOCMPR2 are included in Migrating from CMPR2 to NOCMPR2.
For details on the conversion tools available to upgrade source programs, see Conversion tools for source programs.