Algorithm Design And Problem-solving: Identify Errors In Given Algorithms And Suggest Ways Of Correcting These Errors (Copy)
Algorithm Design And Problem-Solving
Identify Errors In Given Algorithms And Suggest Ways Of Correcting These Errors
Common Algorithm Errors — Quick Identification Table
| Error Type | How It Appears In Questions | Why It Is Wrong | Corrective Action |
|---|---|---|---|
| Syntax error | Missing THEN, ENDIF, incorrect keywords | Algorithm cannot be interpreted logically | Replace with correct Cambridge pseudocode keywords |
| Logic error | Algorithm runs but gives wrong output | Conditions or steps are incorrect | Rewrite condition or reorder steps |
| Runtime error | Division by zero, invalid index | Program crashes during execution | Add validation or condition checks |
| Infinite loop | Loop never terminates | Loop condition never becomes false | Adjust condition or update loop control variable |
| Off-by-one error | Loop runs too many / too few times | Incorrect boundary values | Fix start/end values in loop |
| Uninitialised variable | Variable used before assignment | Value is undefined | Assign initial value before use |
Typical IF Statement Errors
| Error | Example Issue | Correction |
|---|---|---|
| Missing ELSE | Only one outcome handled | Add ELSE to handle alternative case |
| Wrong comparison operator | Using = instead of > |
Use correct relational operator |
| Incorrect condition order | Broad condition before specific | Reorder conditions logically |
Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Loop-Related Errors
| Loop Type | Common Error | Why It Happens | Fix |
|---|---|---|---|
| FOR | Wrong range limits | Misunderstanding inclusive bounds | Correct start/end values |
| WHILE | Condition never changes | Control variable not updated | Update variable inside loop |
| REPEAT-UNTIL | Condition reversed | UNTIL checks for TRUE | Rewrite condition correctly |
Input / Output Errors
| Error | Problem Seen | Correction |
|---|---|---|
| Input after processing | Variable used before input | Move INPUT before calculation |
| Output inside loop unintentionally | Repeated outputs | Move OUTPUT outside loop |
| Wrong variable displayed | Incorrect variable name | Match OUTPUT with correct variable |
Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Variable & Data Handling Errors
| Error | Explanation | Correction |
|---|---|---|
| Wrong data type | Using STRING in arithmetic | Convert or change data type |
| Variable overwrite | Value lost unexpectedly | Use separate variables |
| Scope confusion | Variable inaccessible | Declare variable in correct scope |
Array Errors
| Error | Why It Occurs | How To Fix |
|---|---|---|
| Index out of range | Accessing non-existent element | Adjust index bounds |
| Wrong start index | Assuming arrays start at 1 | Follow given index range |
| Incorrect traversal | Skipping elements | Correct loop increment |
Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Algorithm Tracing Errors
| Error | Description | Correction Strategy |
|---|---|---|
| Incorrect dry run | Skipped steps | Trace line-by-line |
| Variable confusion | Mixing old/new values | Update values immediately |
| Ignoring loop repetition | One-pass tracing | Repeat for every iteration |
Validation & Boundary Errors
| Error | Effect | Fix |
|---|---|---|
| No validation | Invalid data accepted | Add range/type checks |
| Incorrect boundary check | Edge values rejected | Include boundary values |
| Wrong logical operator | Conditions always TRUE/FALSE | Replace AND/OR correctly |
Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Examiner-Focused Correction Tips
| What Examiner Expects | How To Do It |
|---|---|
| Error clearly identified | State exact line or logic |
| Reason explained | Explain why it fails |
| Correction suggested | Give corrected statement |
| No rewriting whole algorithm | Change only faulty part |
| Cambridge keywords used | Use standard pseudocode |
High-Frequency Exam Traps
| Trap | How To Avoid |
|---|---|
| Fixing symptoms not cause | Identify root logic error |
| Over-complicating fix | Use simplest correction |
| Ignoring given constraints | Follow question limits |
| Changing variable names | Keep original identifiers |
Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course