AP CSA Unit 1.1: Sequential Execution Code Tracing Practice

January 5, 2026

Unit 1, Section 1.1

Day 1 Practice • January 7, 2026

🎯 Focus: Understanding Sequential Execution

Practice Question

Consider the following code segment:

int a = 10;
int b = 4;
System.out.println(a + b);
a = a - b;
System.out.println(a * b);

What output is produced when this code segment is executed?

What This Tests: Section 1.1 introduces the fundamental concept that programs execute sequentially—statements run one at a time, in order from top to bottom. This question tests whether you can trace code execution and track how variable values change over time.

Key Concept: Sequential Execution

Sequential execution means statements execute in order from top to bottom. When a variable is reassigned, its old value is replaced.

int x = 5;     // x is 5
x = x + 3;     // x is now 8 (old value gone)
x = x * 2;     // x is now 16 (8 is gone)

Key insight: When you see System.out.println(), that output happens immediately with the current values of variables at that moment. Later changes don't affect earlier output.

Step-by-Step Trace

Line	Code	a	b	Output
1	int a = 10;	10	-
2	int b = 4;	10	4
3	println(a + b);	10	4	14
4	a = a - b;	6	4
5	println(a * b);	6	4	24

Final output: 14, then 24

The key: Line 3 uses the original value of a (10), but Line 5 uses the updated value (6) because Line 4 changed it.

Common Mistakes

Mistake 1: Answer A (14, then 6)

This comes from printing just a instead of a * b. Line 5 prints a * b = 6 * 4 = 24, not just a.

Mistake 2: Answer C (10, then 40)

Using the original value of a (10) for both calculations. By Line 5, a has been reassigned to 6.

Mistake 3: Answer D (14, then 40)

The most common mistake: getting the first output correct but forgetting to update a's value after Line 4.

Mistake 4: Answer E (6, then 24)

Thinking Line 3 prints a after Line 4's change. But Line 3 executes before Line 4, so a is still 10.

Practice Technique

The Code Tracing Table Method

Always create a table when tracing code. This forces you to:

Process each line individually
Update variables when they change
Record output when it happens
Never lose track of current values

Use this on every code tracing question!

Additional Examples

Example: Multiple Reassignments

int x = 5;
System.out.println(x);        // Output: 5
x = x + 3;
System.out.println(x);        // Output: 8
x = x * 2;
System.out.println(x);        // Output: 16

Example: Swapping Values

int a = 7;
int b = 3;
int temp = a;    // temp = 7
a = b;           // a = 3
b = temp;        // b = 7
System.out.println(a + " " + b);  // Output: 3 7

Ready to Level Up Your AP CSA Skills?

Get personalized help or access our complete question bank

Premium Question Bank - Coming Soon! Schedule 1-on-1 Tutoring

300+ Unit 1 questions • Expert tutoring with 1,700+ hours experience • 5.0 rating

Back to blog

Item added to your cart