Yr 11 - Trace tables

• Computing
• Upper Secondary (Key Stage 4)
• GCSE

Trace tables

What is a trace table?

A trace table is a debugging technique used to track the value of variables and outputs, through the flow of a program.

It helps to visualise how the program progresses step by step.

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x

y

output

First step:

Variables and outputs for table headers

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2	6

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2	6
3

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2	6
3	9

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2	6
3	9
4

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2	6
3	9
4	12

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2	6
3	9
4	12
5

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2	6
3	9
4	12
5	15

Pseudocode:

FOR x = 1 to 5

   y = x*3

   x+1

OUTPUT y

x	y	output
1	3
2	6
3	9
4	12
5	15	15

When would you add a value to a trace table?

1. When the software produces an output.
2. When a variable is created.
3. When a variable changes.
4. All are correct.

Challenge 1

a = 4

y = 0

FOR x = 1 to a

    y = y +(x * a)

    x + 1

OUTPUT y

Challenge 2

a = 3, b = 2, y = 0

FOR x = 1 to 5

    IF x MOD 2 = 0 THEN

          y = (a * y) + (b * x)

    ELSE

         y = y + (b * x)

    x + 1

OUTPUT y

Challenge 1

a = 4

y = 0

FOR x = 1 to a

    y = y +(x * a)

    x + 1

OUTPUT y

Score out of 11

a	x	y	output
4		0
	1	4
	2	12
	3	24
	4	40	40

Add up your score out of 11 and enter them below:

Challenge 2

a = 3, b = 2, y = 0

FOR x = 1 to 5

    IF x MOD 2 = 0 THEN

          y = (a * y) + (b * x)

    ELSE

         y = y + (b * x)

x + 1

OUTPUT y

Score out of 14

a	b	x	y	Out
3	2		0
		1	2
		2	10
		3	16
		4	56
		5	66	66

Add up your score out of 14 and enter them below:

Challenge 3:

a = 5, b = 0, c = 1

WHILE c <= a DO

   b = b + c

   c + 1

END WHILE

OUPUT b

a

b

c

output

What is the purpose of a trace table in programming?

1. To write code
2. To track the values of variables
3. to execute the program
4. To design algorthms

In a trace table, each row typically represents:

1. A variable
2. A function
3. A step in the program's execution
4. A loop in the program's flow

Trace tables are particularly useful for:

1. Debugging programs
2. Writing comments
3. Testing hardware
4. Designing user interfaces

How are trace tables helpful in debugging?

1. They write code automatically
2. They highlight syntax errors
3. They track the values of variables during program execution
4. They execute the program