Joined: 06 Jun 2008 Posts: 8165 Location: East Dubuque, Illinois, USA
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.