If–else statement in C - Step-by-Step Execution

Concept Flow - If–else statement

Start

↓

Evaluate condition

Yes No↓

Execute if-block

↓

End

↓

Execute else-block

↓

End

The program checks a condition. If true, it runs the 'if' part; if false, it runs the 'else' part, then ends.

Execution Sample

C

#include <stdio.h>

int main() {
    int x = 10;
    if (x > 5) {
        printf("Greater\n");
    } else {
        printf("Smaller or equal\n");
    }
    return 0;
}

Checks if x is greater than 5 and prints a message accordingly.

Execution Table

Step	Condition (x > 5)	Result	Branch Taken	Output
1	10 > 5	True	if-block	"Greater\n" printed
2	End of if-else	-	-	Program ends

💡 Condition true, so if-block executed; else-block skipped.

Variable Tracker

Variable	Start	After Condition Check	Final
x	10	10	10

Key Moments - 2 Insights

Why does the else-block not run even though it exists?

Because the condition (x > 5) is true at step 1 in the execution_table, so only the if-block runs.

What happens if the condition is false?

The else-block runs instead, as shown by the 'Branch Taken' column in the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output at step 1?

A No output

B "Greater\n" printed

C "Smaller or equal\n" printed

D Error message

💡 Hint

Check the 'Output' column in the first row of execution_table.

At which step does the program decide which branch to take?

A Step 2

B Before Step 1

C Step 1

D After Step 2

💡 Hint

Look at the 'Condition' and 'Branch Taken' columns in execution_table row 1.

If x was 3 instead of 10, which branch would be taken?

A else-block

B if-block

C Both if and else blocks

D Neither block

💡 Hint

Refer to the condition (x > 5) and what happens when it is false.

Concept Snapshot

if (condition) {
  // code runs if condition true
} else {
  // code runs if condition false
}
Checks condition once, runs one branch only.

Full Transcript

This example shows how an if-else statement works in C. The program sets x to 10, then checks if x is greater than 5. Since 10 is greater than 5, it prints "Greater" and skips the else part. The flow diagram shows the decision path. The execution table tracks the condition check and output. Variables remain unchanged. Key points clarify why only one branch runs. The quiz tests understanding of output, decision step, and behavior if x changes.