Coding Sheets, Practice & Learning Support: Algorithm Tracing Practice Worksheets (Copy)

Algorithm Tracing Practice Worksheets

How To Use These Worksheets Properly

• For each question:
  • Trace line by line
  • Update variables in order
  • Do not skip iterations
• Marks are awarded for:
  • Correct intermediate values
  • Correct final output
• Always use a trace table, even if not asked

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Worksheet 1: Basic FOR Loop Tracing

Algorithm

total ← 0

FOR i ← 1 TO 5
  total ← total + i
NEXT i

OUTPUT total

Student Task

• Complete the trace table
• State the final output

Trace Table

i	total before	total after
1	0
2
3
4
5

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Worksheet 2: FOR Loop With Conditional

Algorithm

count ← 0

FOR i ← 1 TO 8
  IF i MOD 2 = 0 THEN
    count ← count + 1
  ENDIF
NEXT i

OUTPUT count

Student Task

• Trace only when condition is TRUE
• Identify which values increment count

Trace Table

i	i MOD 2 = 0	count
1
2
3
4
5
6
7
8

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course

Worksheet 3: WHILE Loop Tracing

Algorithm

x ← 10
count ← 0

WHILE x > 0 DO
  x ← x - 3
  count ← count + 1
ENDWHILE

OUTPUT x
OUTPUT count

Student Task

• Trace until loop condition becomes FALSE
• Record final values of x and count

Trace Table

Iteration	x before	x after	count
1
2
3
4

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Worksheet 4: REPEAT UNTIL Loop Tracing

Algorithm

total ← 0
num ← 0

REPEAT
  num ← num + 2
  total ← total + num
UNTIL num >= 10

OUTPUT total

Student Task

• Remember: REPEAT runs at least once
• Stop when condition becomes TRUE

Trace Table

Step	num	total	num >= 10
1
2
3
4
5

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course

Worksheet 5: Flag-Controlled Loop Tracing

Algorithm

found ← FALSE
i ← 1
arr ← [4, 7, 9, 2, 6]
target ← 2

WHILE i <= 5 AND found = FALSE DO
  IF arr[i] = target THEN
    found ← TRUE
  ELSE
    i ← i + 1
  ENDIF
ENDWHILE

OUTPUT i
OUTPUT found

Student Task

• Identify where the loop stops
• Trace both i and found

Trace Table

i	arr[i]	found before	found after
1
2
3
4

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Worksheet 6: Sentinel-Controlled Loop Tracing

Algorithm

total ← 0

REPEAT
  INPUT num
  IF num <> -1 THEN
    total ← total + num
  ENDIF
UNTIL num = -1

OUTPUT total

Input Sequence

3, 5, 2, -1

Student Task

• Show how sentinel is excluded
• Calculate final total

Trace Table

Input num	num = -1	total
3
5
2
-1

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course

Worksheet 7: Array Traversal Tracing

Algorithm

arr ← [2, 4, 6, 8, 10]
sum ← 0

FOR i ← 1 TO 5
  sum ← sum + arr[i]
NEXT i

OUTPUT sum

Student Task

• Trace each array access
• Track cumulative sum

Trace Table

i	arr[i]	sum
1
2
3
4
5

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Worksheet 8: Maximum-Finding Trace

Algorithm

arr ← [5, 3, 9, 1, 6]
max ← arr[1]

FOR i ← 2 TO 5
  IF arr[i] > max THEN
    max ← arr[i]
  ENDIF
NEXT i

OUTPUT max

Student Task

• Track when max changes

Trace Table

i	arr[i]	max before	max after
2
3
4
5

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course

Worksheet 9: Nested Loop Tracing (2D Table)

Algorithm

total ← 0
table ← [[1,2,3],[4,5,6]]

FOR row ← 1 TO 2
  FOR col ← 1 TO 3
    total ← total + table[row][col]
  NEXT col
NEXT row

OUTPUT total

Student Task

• Trace row-by-row
• Track cumulative total

Trace Table

row	col	table[row][col]	total
1	1
1	2
1	3
2	1
2	2
2	3

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Worksheet 10: Bubble Sort Single-Pass Trace

Algorithm (One Pass Only)

arr ← [6, 2, 4, 1]

FOR j ← 1 TO 3
  IF arr[j] > arr[j + 1] THEN
    temp ← arr[j]
    arr[j] ← arr[j + 1]
    arr[j + 1] ← temp
  ENDIF
NEXT j

OUTPUT arr

Student Task

• Trace only one pass
• Show array after each comparison

Trace Table

j	Compared	Swap?	Array After
1	arr[1], arr[2]
2	arr[2], arr[3]
3	arr[3], arr[4]

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course

Universal Tracing Checklist (Exam Use)

• Initialise variables first
• Evaluate loop condition before each iteration
• Update variables in correct order
• Stop immediately when condition fails
• Final output comes after loop ends

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Generic Trace Table Templates (Copy For Any Question)

Loop Tracing

Iteration	Variable(s) Before	Condition	Variable(s) After	Output

Array Tracing

Index	Value Accessed	Key Variables	Output

Flag Tracing

Step	Index	Condition Met	Flag	Loop Continues

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course