Nested conditional statements - Step-by-Step Execution

Concept Flow - Nested conditional statements

Start

↓

Check Condition A

|Yes↓

Check Condition B

|Yes↓

Execute Block 1

↓

End

No↓

Execute Block 2

↓

End

No↓

Execute Block 3

↓

End

First, check the outer condition. If true, check the inner condition. Depending on inner condition, execute one block. If outer condition is false, execute another block.

Execution Sample

C

int x = 10;
int y = 20;
if (x > 5) {
  if (y > 15) {
    printf("Both conditions true\n");
  } else {
    printf("Only x > 5\n");
  }
} else {
  printf("x <= 5\n");
}

This code checks if x is greater than 5, then inside that, checks if y is greater than 15, printing messages accordingly.

Execution Table

Step	Condition Checked	Result	Branch Taken	Output
1	x > 5 (10 > 5)	True	Enter inner if
2	y > 15 (20 > 15)	True	Print 'Both conditions true'	Both conditions true
3	End of if-else	-	-	-

💡 All conditions evaluated; program ends after printing message.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
x	10	10	10	10
y	20	20	20	20

Key Moments - 2 Insights

Why does the program check y > 15 only after confirming x > 5?

Because the inner if is nested inside the outer if, so y > 15 is checked only if x > 5 is true (see execution_table step 1 and 2).

What happens if x <= 5?

The program skips the inner if and executes the else block for the outer if (not shown in this run, but would print 'x <= 5').

Visual Quiz - 3 Questions

Look at the execution table, what is the output at step 2?

A "x <= 5"

B "Only x > 5"

C "Both conditions true"

D No output

💡 Hint

Check the Output column at step 2 in the execution_table.

At which step does the program decide not to check y > 15?

A Step 2

B Step 1

C Step 3

D Never

💡 Hint

If x > 5 is false at step 1, inner condition y > 15 is skipped.

If x was 3, what would be the output?

A "x <= 5"

B "Only x > 5"

C "Both conditions true"

D No output

💡 Hint

Refer to key_moments about what happens if x <= 5.

Concept Snapshot

Nested conditionals check one condition inside another.
Syntax: if (cond1) { if (cond2) { ... } else { ... } } else { ... }
Inner condition runs only if outer is true.
Use to test multiple related conditions step-by-step.

Full Transcript

This example shows nested conditional statements in C. First, the program checks if x is greater than 5. If yes, it then checks if y is greater than 15. Depending on these checks, it prints different messages. The execution table traces these steps, showing conditions checked, results, branches taken, and output. Variables x and y remain unchanged during execution. Key moments clarify why inner conditions depend on outer ones and what happens if the outer condition is false. The quiz tests understanding of output and flow based on the execution trace.