Have you reviewed the COBOL Language Reference (manuals link at the top of the page) on the PERFORM statement?
PERFORM paragraph performs only that paragraph. So case 1 would execute the PERFORM, then A8-Para, then D-para, then at the end of A8-Para would return to A0-section and continue. If there's no program exit, control would fall through A0-Exit and start executing A8-Para and so forth.
The main difference in case 2 in that execution would go through the end paragraph, but otherwise there's no difference in execution sequence.
Joined: 22 Apr 2006 Posts: 6258 Location: Mumbai, India
There is no difference in both the approaches from execution per se as Robert has said; though at some shops coding "..thru AB-para-end" in "Perform AB-para thru AB-para-end" comes under coding standards. Every PARA should end with an EXIT though period (.) in place of EXIT would also do the same.