Section 8: Program Editing131
You have seen how SST can be used in normal or USER mode to execute a program one line at a time. Using SST in this manner can help you create programs and locate errors in them. Now let’s see how you can use SST , BST , and GTO · nnn in PRGM mode to help you modify a program.
Modifying a Program
Since you have just completed the execution of the AREA program, the calculator is set back to the beginning of the program. You can verify this by placing the calculator into PRGM mode (press PRGM ). Press SST once to see the program label.
Keystrokes Display    
  01 REG 40    
  01 LBLTAREA     
  The line number and instruction are displayed in PRGM mode.
Now let’s modify the AREA program so that the X-register contents will automatically be displayed at certain points in the program. We will accomplish this by placing PSE (pause) instructions in the program to halt the program and display the contents of the X-register for about one second, then resume execution. (More about PSE later.)
  01 LBLTAREA     
  02 STO 01    
  03 X 2    
  04 PI    
  05 *    
  06 2    
  We will insert a PSE after this line
  07 * 
  to display the area of the top and
  08 X<>Y    
  of the cylinder ...
  09 RCL 01    
  10 *    
  11 PI    
  12 *    
  13 2    
  ... and a PSE after this line to
  07 * 
  display the area of the cylinder with-
  15 +    
  out the top and bottom.
  16 END    
To begin modifying your program, reset the calculator to line 0 of AREA.
Keystrokes Display    
g GTO · · 
  00 REG 40