When the PL/I perspective switches to the debug perspective, the source file opdemo.pli should automatically display with the OPDEMO: PROC(JCLPARM) OPTIONS(MAIN) REORDER; line highlighted as the current line of execution.
 or press F5 to step into the program. This takes you to line 77 that reads:
 or press F5 to step into the program. This takes you to line 77 that reads: 
                  		  on error begin;
 two more times to get to the line that reads:
 two more times to get to the line that reads: 
                  		  ON ENDFILE (SYSIN)
OPDEMO, SYSIN FILE RECORD INPUT ENVIRONMENT(FB RECSIZE(80)); Refs=4.
 two more times to get to the line that reads:
 two more times to get to the line that reads: 
                  		  SYSPRINT_BUFF = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' || /* 26 */
 and see how the value of 
                  		  SYSPRINT_BUFF changes to 
                  		  ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ12.
 and see how the value of 
                  		  SYSPRINT_BUFF changes to 
                  		  ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ12. 
                  		
                a few more times until you reach the line that reads:
 a few more times until you reach the line that reads: 
                  		  sysin_num_recs = '0';
This line initiates the SYSIN_NUM_RECS variable.
 and check the value of 
                  		  SYSIN_NUM_RECS in the Expressions pane. It has changed to 
                  		  0000.
 and check the value of 
                  		  SYSIN_NUM_RECS in the Expressions pane. It has changed to 
                  		  0000. 
                  		
                a few more times until you reach the line that reads:
 a few more times until you reach the line that reads: 
                  		  sysin_num_recs = sysin_num_recs + 1;
 (or 
                  		  CTRL+R) to run the program to that line.
 (or 
                  		  CTRL+R) to run the program to that line. 
                  		  
                  When the debugger reaches the END statement, you can see from the final value of SYSIN_NUM_RECS (0004) that the program has processed five records.
 .
.