SDD error types and detection
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The document discusses different types of errors in software development - logic errors, syntax errors, and runtime errors. It provides examples of each type of error and describes methods for detecting and debugging errors, such as focusing on specific modules, using debugging output statements, stubs, flags, and programming tools like breakpoints. Overall, the document aims to help programmers understand error types and strategies for locating errors in code.
SDD error types and detection
- 1. SOFTWARE DESIGN & DEVELOPMENT ON LINE WITH MR CUSACK
- 2. LESSON TOPIC T3W2 – ERROR TYPES & DETECTION
- 3. WHAT TYPES OF ERROR ARE THERE? HINT: THERE ARE 3 TYPES!
- 4. ERROR TYPES AND DETECTION SCENARIO: AFTER USING A SOLUTION FOR SOME TIME USERS REPORT THAT SOME OUTPUTS ARE NOT AS EXPECTED.
- 5. ERROR TYPES AND DETECTION SCENARIO: AFTER USING A SOLUTION FOR SOME TIME USERS REPORT THAT SOME OUTPUTS ARE NOT AS EXPECTED. WHAT TYPE OF ERROR ?
- 6. ERROR TYPES AND DETECTION SCENARIO: AFTER USING A SOLUTION FOR SOME TIME USERS REPORT THAT SOME OUTPUTS ARE NOT AS EXPECTED. WHAT TYPE OF ERROR ?...... LOGIC ERROR
- 7. ERROR TYPES AND DETECTION SCENARIO: AFTER USING A SOLUTION FOR SOME TIME USERS REPORT THAT SOME OUTPUTS ARE NOT AS EXPECTED. WHAT TYPE OF ERROR ?...... LOGIC ERROR WHY NOT A SYNTAX ERROR ?
- 8. ERROR TYPES AND DETECTION SCENARIO: AFTER USING A SOLUTION FOR SOME TIME USERS REPORT THAT SOME OUTPUTS ARE NOT AS EXPECTED. WHAT TYPE OF ERROR ?...... LOGIC ERROR WHY NOT A SYNTAX ERROR ? WHY NOT A RUNTIME ERROR ?
- 9. ERROR TYPES AND DETECTION SCENARIO: A PROGRAMMER COMPLETES CODING. SHE ATTEMPTS TO CREATE AN EXECUTABLE SOLUTION. THIS FAILS. WHAT TYPE OF ERROR ?
- 10. ERROR TYPES AND DETECTION SCENARIO: A PROGRAMMER COMPLETES CODING. SHE ATTEMPTS TO CREATE AN EXECUTABLE SOLUTION. THIS FAILS. WHAT TYPE OF ERROR ? SYNTAX ERROR !
- 11. ERROR TYPES AND DETECTION SCENARIO: A PROGRAMMER COMPLETES CODING. SHE ATTEMPTS TO CREATE AN EXECUTABLE SOLUTION. THIS FAILS. WHAT TYPE OF ERROR ? SYNTAX ERROR ! DESCRIBE WHAT HAS CAUSED THIS ERROR
- 12. ERROR TYPES AND DETECTION SCENARIO: A PROGRAMMER COMPLETES CODING. SHE ATTEMPTS TO CREATE AN EXECUTABLE SOLUTION. THIS FAILS. WHAT TYPE OF ERROR ? SYNTAX ERROR ! DESCRIBE WHAT HAS CAUSED THIS ERROR AT SOME POINT IN THE CODING THE PROGRAMMER HAS ENTERED CODE THAT DOES NOT COMPLY WITH THE RULES THAT APPLY TO THIS LANGUAGE. I.E. NOT COMPLIED WITH THE SYNTAX RULES FOR THAT LANGUAGE.
- 13. ERROR TYPES AND DETECTION SCENARIO: A PROGRAMMER COMPLETES CODING. SHE ATTEMPTS TO CREATE AN EXECUTABLE SOLUTION. THIS FAILS. WHAT TYPE OF ERROR ? SYNTAX ERROR ! WHAT IS AVAILABLE TO THE PROGRAMMER TO HELP AVOID THIS ?
- 14. ERROR TYPES AND DETECTION SCENARIO: A PROGRAMMER COMPLETES CODING. SHE ATTEMPTS TO CREATE AN EXECUTABLE SOLUTION. THIS FAILS. WHAT TYPE OF ERROR ? SYNTAX ERROR ! WHAT IS AVAILABLE TO THE PROGRAMMER TO HELP AVOID THIS ? METALANGUAGES !
- 15. ERROR TYPES AND DETECTION SCENARIO: A PROGRAMMER COMPLETES CODING. SHE ATTEMPTS TO CREATE AN EXECUTABLE SOLUTION. THIS FAILS. WHAT TYPE OF ERROR ? SYNTAX ERROR ! WHAT IS AVAILABLE TO THE PROGRAMMER TO HELP AVOID THIS ? SYNTAX DEFINITIONS AND HELP IN THE FORM OF METALANGUAGES SUCH AS EBNF AND RAILROAD DIAGRAMS MESSAGES WITHIN THE PROGRAMMING ENVIRONMENT THAT REPORT SYNTAX ERRORS AND SUGGEST CORRECTIONS
- 16. ERROR TYPES AND DETECTION SCENARIO: A PROGRAM HAS BEEN SUCCESSFULLY RUNNING FOR SOME TIME. A USER REPORTS THAT THE PROGRAM HAS “CRASHED”. WHAT TYPE OF ERROR ?
- 17. ERROR TYPES AND DETECTION SCENARIO: A PROGRAM HAS BEEN SUCCESSFULLY RUNNING FOR SOME TIME. A USER REPORTS THAT THE PROGRAM HAS “CRASHED”. WHAT TYPE OF ERROR ? RUNTIME ERROR
- 18. ERROR TYPES AND DETECTION SCENARIO: A PROGRAM HAS BEEN SUCCESSFULLY RUNNING FOR SOME TIME. A USER REPORTS THAT THE PROGRAM HAS “CRASHED”. WHAT TYPE OF ERROR ? RUNTIME ERROR HOW IS THIS DIFFERENT TO A LOGIC ERROR ?
- 19. ERROR TYPES AND DETECTION SCENARIO: A PROGRAM HAS BEEN SUCCESSFULLY RUNNING FOR SOME TIME. A USER REPORTS THAT THE PROGRAM HAS “CRASHED”. WHAT TYPE OF ERROR ? RUNTIME ERROR HOW IS THIS DIFFERENT TO A LOGIC ERROR ? LOGIC ERRORS USUALLY ALLOW THE PROGRAM TO CONTINUE TO RUN…BUT GIVE UNEXPECTED RESULTS. RUNTIME ERRORS CRASH (OR REQUIRE RECOVERY)
- 20. ERROR TYPES AND DETECTION SCENARIO: A PROGRAM HAS BEEN SUCCESSFULLY RUNNING FOR SOME TIME. A USER REPORTS THAT THE PROGRAM HAS “CRASHED”. WHAT TYPE OF ERROR ? RUNTIME ERROR WHAT DID THE USER DO THAT MADE THIS HAPPEN ?
- 21. ERROR TYPES AND DETECTION SCENARIO: A PROGRAM HAS BEEN SUCCESSFULLY RUNNING FOR SOME TIME. A USER REPORTS THAT THE PROGRAM HAS “CRASHED”. WHAT TYPE OF ERROR ? RUNTIME ERROR WHAT DID THE USER DO THAT MADE THIS HAPPEN ? PROBABLY ENTERED UNEXPECTED OR INAPPROPRIATE DATA ..OR CREATED EVENTS THAT ARE NOT NORMAL.. ..OR WERE NOT ANTICIPATED BY THE PROGRAMMER.
- 22. ERROR TYPES AND DETECTION SCENARIO: A PROGRAM HAS BEEN SUCCESSFULLY RUNNING FOR SOME TIME. A USER REPORTS THAT THE PROGRAM HAS “CRASHED”. WHAT TYPE OF ERROR ? RUNTIME ERROR WAS THIS THE USERS FAULT ?
- 23. ERROR TYPES AND DETECTION SCENARIO: A PROGRAM HAS BEEN SUCCESSFULLY RUNNING FOR SOME TIME. A USER REPORTS THAT THE PROGRAM HAS “CRASHED”. WHAT TYPE OF ERROR ? RUNTIME ERROR. WHAT DID THE USER DO THAT MADE THIS HAPPEN ? WAS THIS THE USERS FAULT ? NO ! THE DEVELOPER SHOULD HAVE ALLOWED FOR THIS POSSIBILITY AND INCLUDED ADEQUATE TRAPS OR CODE SO THAT THE USER CANNOT CAUSE THIS TO HAPPEN
- 24. ERROR TYPES SUMMARY LOGIC ERRORS SYNTAX ERRORS RUNTIME ERRORS
- 25. ERROR TYPES SUMMARY LOGIC ERRORS SYNTAX ERRORS RUNTIME ERRORS HOW CAN THESE BE DETECTED BEFORE THE SOLUTION GOES TO THE CLIENTS ?
- 26. LOGIC ERRORS HOW CAN THESE BE DETECTED BEFORE THE SOLUTION GOES TO THE CLIENTS ?
- 27. LOGIC ERRORS HOW CAN THESE BE DETECTED BEFORE THE SOLUTION GOES TO THE CLIENTS ? THOROUGH CREATION OF TEST DATA AND DESK CHECKING AT PLANNING STAGE REPEATING OF THIS TESTING AFTER IMPLEMENTATION
- 28. SYNTAX ERRORS HOW CAN THESE BE DETECTED BEFORE THE SOLUTION GOES TO THE CLIENTS ?
- 29. SYNTAX ERRORS HOW CAN THESE BE DETECTED BEFORE THE SOLUTION GOES TO THE CLIENTS ? IN MOST PROGRAMMING ENVIRONMENTS THE PROGRAMMING TOOL REPORTS SUCH ERRORS EITHER AS CODE IS CREATED OR WHEN AN ATTEMPT IS MADE TO TRANSLATE THE CODE. THESE ARE DETECTED BECAUSE THE PROGRAM WON’T RUN !
- 30. RUNTIME ERRORS HOW CAN THESE BE DETECTED BEFORE THE SOLUTION GOES TO THE CLIENTS ? (PROBABLY THE MOST DIFFICULT TO DETECT)
- 31. RUNTIME ERRORS HOW CAN THESE BE DETECTED BEFORE THE SOLUTION GOES TO THE CLIENTS ? (PROBABLY THE MOST DIFFICULT TO DETECT) AT BOTH THE PLANNING AND DURING IMPLEMENTATION AND TESTING THE DEVELOPER HAS TO PREDICT WHAT USERS CAN DO AND CREATE TEST DATA SETS TO ENSURE THAT ALL OF THESE POSSIBILITIES ARE COVERED.
- 32. RUNTIME ERRORS HOW CAN THESE BE DETECTED BEFORE THE SOLUTION GOES TO THE CLIENTS ? (PROBABLY THE MOST DIFFICULT TO DETECT) AT BOTH THE PLANNING AND DURING IMPLEMENTATION AND TESTING THE DEVELOPER HAS TO PREDICT WHAT USERS CAN DO AND CREATE TEST DATA SETS TO ENSURE THAT ALL OF THESE POSSIBILITIES ARE COVERED. IN THE CASE OF LARGER SOLUTION RUNTIME ERROR DETECTION IS OFTEN ACHIEVED BY EXTENSIVE BETA TESTING. IN THIS CASE MANY USERS ARE ASKED TO RUN THE SOLUTION AND REPORT BACK PROBLEMS. THIS IS ANOTHER WAY TO HOPEFULLY TEST THE UNEXPECTED.
- 33. AN EXAMPLE A PROGRAM TO FIND THE AVERAGE OF 5 ELEMENTS IN AN ARRAY
- 34. AN EXAMPLE A PROGRAM TO FIND THE AVERAGE OF 5 ELEMENTS IN AN ARRAY BEGIN SET TOTAL TO 0 SET COUNTER TO 1 WHILE COUNTER <5 TOTAL = TOTAL + ARRAY(COUNTER) INCREMENT COUNTER ENDWHILE AVERAGE = TOTAL /COUNTER END
- 35. AN EXAMPLE A PROGRAM TO FIND THE AVERAGE OF 5 ELEMENTS IN AN ARRAY BEGIN SET TOTAL TO 0 SET COUNTER TO 1 WHILE COUNTER <5 TOTAL = TOTAL + ARRAY(COUNTER) INCREMENT COUNTER ENDWHILE AVERAGE = TOTAL /COUNTER END LOGIC ERROR
- 36. AN EXAMPLE A PROGRAM TO FIND THE AVERAGE OF 5 ELEMENTS IN AN ARRAY VB CODE WHILE COUNTER < 5 MAKE THE TOTAL = TOTAL + ARRAY (COUNTER) ENDDO
- 37. AN EXAMPLE A PROGRAM TO FIND THE AVERAGE OF 5 ELEMENTS IN AN ARRAY VB CODE…. BEHIND THE AVERAGE BUTTON. WHILE COUNTER < 5 MAKE THE TOTAL = TOTAL + ARRAY (COUNTER) ENDDO SYNTAX ERROR
- 38. AN EXAMPLE A PROGRAM TO FIND THE AVERAGE OF NUMBERS THAT THE USER ENTERS LETS ASSUME THAT THE ALGORITHM DESKCHECKED OK LETS ASSUME THAT THE EXE WAS CREATED OK
- 39. AN EXAMPLE A PROGRAM TO FIND THE AVERAGE OF NUMBERS THAT THE USER ENTERS LETS ASSUME THAT THE ALGORITHM DESKCHECKED OK LETS ASSUME THAT THE EXE WAS CREATED OK NOW THE USER RUNS THE PROGRAM…SEVERAL TIMES AND IT GIVES CORRECT RESULTS EVERY TIME
- 40. AN EXAMPLE A PROGRAM TO FIND THE AVERAGE OF NUMBERS THAT THE USER ENTERS LETS ASSUME THAT THE ALGORITHM DESKCHECKED OK LETS ASSUME THAT THE EXE WAS CREATED OK NOW THE USER RUNS THE PROGRAM…SEVERAL TIMES AND IT GIVES CORRECT RESULTS EVERY TIME THEN THE USER RUNS THE PROGRAM AGAIN. ENTERS NO NUMBERS AND CLICKS THE AVERAGE BUTTON
- 41. AN EXAMPLE A PROGRAM TO FIND THE AVERAGE OF NUMBERS THAT THE USER ENTERS LETS ASSUME THAT THE ALGORITHM DESKCHECKED OK LETS ASSUME THAT THE EXE WAS CREATED OK NOW THE USER RUNS THE PROGRAM…SEVERAL TIMES AND IT GIVES CORRECT RESULTS EVERY TIME THEN THE USER RUNS THE PROGRAM AGAIN. ENTERS NO NUMBERS AND CLICKS THE AVERAGE BUTTON RUNTIME ERROR….DIVISION BY ZERO
- 42. FIXING BUGS SCENARIO: YOU HAVE COMPLETED CODING AND ATTEMPT TO RUN YOUR (LARGE MODULAR) PROGRAM. EITHER A RUNTIME OR A LOGIC ERROR IS APPARENT. HOW CAN YOU FIND AND FIX THE ERROR ?
- 43. ERROR DETECTION TOOLS 1. FOCUS ON MODULES.
- 44. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS
- 45. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS 3. STUBS
- 46. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS 3. STUBS 4. FLAGS
- 47. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS 3. STUBS 4. FLAGS 5. PROGRAMMING TOOLS….BREAKPOINTS, STEPPING, WATCH EXPRESSIONS
- 48. AN EXAM QUESTION A LARGE AND COMPLEX PROGRAM CONTAINS MANY MODULES THAT MANIPULATE DATA. THE PROGRAM PRODUCES INCORRECT OUTPUT, POSSIBLY AS A RESULT OF CALCULATION ERRORS IN ONE OR MORE MODULES. DESK CHECKING THE SOURCE CODE AND PEER CHECKING ARE TWO TECHNIQUES THAT COULD BE USED TO DEBUG THIS PROGRAM. DESCRIBE HOW OTHER TECHNIQUES COULD BE USED TO HELP LOCATE THE ERRORS IN THIS PROGRAM. HSC 2012
- 49. AN EXAM QUESTION A LARGE AND COMPLEX PROGRAM CONTAINS MANY MODULES THAT MANIPULATE DATA. THE PROGRAM PRODUCES INCORRECT OUTPUT, POSSIBLY AS A RESULT OF CALCULATION ERRORS IN ONE OR MORE MODULES. DESK CHECKING THE SOURCE CODE AND PEER CHECKING ARE TWO TECHNIQUES THAT COULD BE USED TO DEBUG THIS PROGRAM. DESCRIBE HOW OTHER TECHNIQUES COULD BE USED TO HELP LOCATE THE ERRORS IN THIS PROGRAM. YOU COULD USE A PROGRAM TRACE TOGETHER WITH A VARIABLE WATCHER TO CHECK THE CONTENTS OF VARIABLES AT EACH RELEVANT STEP IN THE PROGRAM – TO MAKE SURE VALUES ARE CALCULATED CORRECTLY. BREAK POINTS SET IN KEY SUBROUTINES – IN CONJUNCTION WITH A TRACE – CAN BE USED TO ENSURE THESE SUBROUTINES ARE EXECUTED AND THAT CRITICAL VARIABLES CONTAIN THE EXPECTED VALUES AT THESE POINTS IN THE EXECUTION. THE USE OF DEBUGGING OUTPUT STATEMENTS AND FLAGS WILL ALSO ENSURE THAT THE VARIOUS MODULES ARE EXECUTED APPROPRIATELY.
- 50. ERROR DETECTION TOOLS 1. FOCUS ON MODULES FIND IN WHICH MODULE THE ERROR OCCURS. DETERMINE WHAT THE USER WAS DOING WHEN THE ERROR HAPPENED ? THEN FOCUS YOUR DETECTION METHODS ON THAT MODULE.
- 51. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS INSERT TEMPORARY OUTPUTS (LABELS) THAT TELL US THE VALUE OF KEY VARIABLES. REMOVE THESE WHEN THE ERROR IS FIXED.
- 52. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS INSERT TEMPORARY OUTPUTS (LABELS) THAT TELL US THE VALUE OF KEY VARIABLES. REMOVE THESE WHEN THE ERROR IS FIXED. WHAT WOULD BE APPROPRIATE DEBUGGING OUTPUTS IN THE PREVIOUS AVERAGE CALCULATOR ?
- 53. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS INSERT TEMPORARY OUTPUTS (LABELS) THAT TELL US THE VALUE OF KEY VARIABLES. REMOVE THESE WHEN THE ERROR IS FIXED. WHAT WOULD BE APPROPRIATE DEBUGGING OUTPUTS IN THE PREVIOUS AVERAGE CALCULATOR ? OUTPUT: THE COUNTER, THE TOTAL TEMPORARILY !
- 54. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS 3. STUBS PARTIALLY COMPLETED MODULES (“UNDER CONSTRUCTION”) THAT TELL US THAT NAVIGATION TO A MODULE HAS WORKED AND THAT PARAMETERS HAVE BEEN SUCCESSFULLY PASSED. PROGRESSIVELY USE THESE TO REPLACE MODULES IN ORDER TO ISOLATE THE PROBLEM.
- 55. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS 3. STUBS 4. FLAGS A SIMPLE BOOLEAN VARIABLE THAT RECORDS A “TRUE” WHEN CERTAIN PARTS OF A PROGRAM ARE ACCESSED OR STATUSES REACHED. OUTPUT THIS AS A DEBUGGING OUTPUT STATEMENT. USEFUL TO SEE IF CONDITIONS IN SELECTION AND ITERATION HAVE BEEN MET.
- 56. ERROR DETECTION TOOLS 1. FOCUS ON MODULES. 2. DEBUGGING OUTPUT STATEMENTS 3. STUBS 4. FLAGS 5. PROGRAMMING TOOLS….BREAKPOINTS, STEPPING, WATCH EXPRESSIONS THESE ARE DEALT WITH IN THE VB EXERCISES. ESSENTIALLY THESE CAN STEP THROUGH OR STOP EXECUTION…AND DISPLAY THE CURRENT VALUES OF VARIABLES. TURNS A BLACK BOX TEST INTO A WHITE BOX TEST.
- 57. WHITE BOX TEST: We see what is changing inside. We trace the changes in variables. We know the inputs (test data) and the expected outputs Deskchecks when in the planning stage Breakpoints and debugging output statements when in the implementation stage
- 58. BLACK BOX TEST: We only know the inputs (test data) and the outputs We compare these outputs with what is expected. If actual and expected don’t match……. We start debugging !
- 59. WHEN WE WORK TOGETHER WE ACHIEVE A LOT IT’S ALL ABOUT TEAMWORK!
- 60. THANKS FOR JOINING SDD