Assignment operators in C - Step-by-Step Execution

Concept Flow - Assignment operators

Start

↓

Evaluate Right Side

↓

Apply Operator (=, +=, -=, etc.)

↓

Update Left Variable

↓

End

The program evaluates the right side expression, applies the assignment operator to update the left variable, then continues.

Execution Sample

C

int a = 5;
a += 3;
a *= 2;

This code assigns 5 to a, then adds 3 to a, then multiplies a by 2.

Execution Table

Step	Code Line	Variable 'a' Before	Operation	Variable 'a' After
1	int a = 5;	undefined	Assign 5	5
2	a += 3;	5	Add 3 (a = a + 3)	8
3	a *= 2;	8	Multiply by 2 (a = a * 2)	16
4	End	16	No operation	16

💡 All assignment operations completed, program ends.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
a	undefined	5	8	16	16

Key Moments - 3 Insights

Why does 'a += 3;' change 'a' from 5 to 8?

Because 'a += 3;' means 'a = a + 3', so it adds 3 to the current value of 'a' which was 5, resulting in 8 (see execution_table step 2).

What happens if we use '=' instead of '+='?

Using '=' assigns the right side value directly, so 'a = 3;' would set 'a' to 3, ignoring its previous value (not shown in this trace but similar to step 1).

Does 'a *= 2;' multiply the old or new value of 'a'?

'a *= 2;' multiplies the current value of 'a' after previous operations, which is 8, so it becomes 16 (see execution_table step 3).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'a' after step 2?

A 16

B 5

C 8

D 3

💡 Hint

Check the 'Variable a After' column in execution_table row for step 2.

At which step does 'a' become 16?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Variable a After' column and find when it changes to 16.

If we replace 'a += 3;' with 'a = 3;', what would be the value of 'a' after step 2?

A 3

B 8

C 5

D 16

💡 Hint

Remember '=' assigns the right side value directly, ignoring previous 'a' value.

Concept Snapshot

Assignment operators in C:
- '=' assigns value: a = 5;
- '+=' adds and assigns: a += 3; means a = a + 3;
- '*=' multiplies and assigns: a *= 2; means a = a * 2;
- They update the variable on the left with the result of the operation.
- Useful for short, clear updates to variables.

Full Transcript

This visual trace shows how assignment operators work in C. First, variable 'a' is assigned 5. Then 'a += 3;' adds 3 to 'a', making it 8. Next, 'a *= 2;' multiplies 'a' by 2, making it 16. Each step updates 'a' based on the operator used. The trace helps understand how these operators change variable values step-by-step.