Type casting in C++ - Step-by-Step Execution

Concept Flow - Type casting

Start with a value

↓

Choose target type

↓

Apply cast syntax

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Convert value to target type

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Use converted value

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End

Type casting changes a value from one type to another using explicit syntax, allowing different operations or storage.

Execution Sample

C++

int main() {
  double pi = 3.14;
  int intPi = (int)pi;
  return intPi;
}

This code converts a double value 3.14 to an int by cutting off the decimal part.

Execution Table

Step	Variable	Original Value	Cast Type	Result after Cast	Explanation
1	pi	3.14 (double)	-	3.14 (double)	Initial double value assigned
2	intPi	3.14 (double)	int	3 (int)	Cast double to int truncates decimal
3	return	intPi	-	3	Return the integer value
4	-	-	-	-	Program ends

💡 Program ends after returning the casted integer value 3

Variable Tracker

Variable	Start	After Cast	Final
pi	3.14 (double)	3.14 (double)	3.14 (double)
intPi	uninitialized	3 (int)	3 (int)

Key Moments - 3 Insights

Why does casting from double to int remove the decimal part?

Casting from double to int truncates the decimal part instead of rounding, as shown in step 2 of the execution_table where 3.14 becomes 3.

Is the original variable 'pi' changed after casting?

No, 'pi' remains a double with value 3.14. The cast creates a new int value in 'intPi' as shown in variable_tracker.

What happens if you cast an int to a double?

Casting int to double converts the integer to a floating-point number with decimal zero, e.g., 3 becomes 3.0, but this example shows double to int.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'intPi' after casting?

A 3.14

B 3

C 0

D 4

💡 Hint

Check step 2 in the execution_table where 'intPi' is assigned after casting.

At which step does the decimal part get removed?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look at the 'Explanation' column in execution_table for when casting happens.

If we changed the cast to (float) instead of (int), what would 'intPi' hold?

A 0

B 3.14 (float)

C 3 (int)

D Error

💡 Hint

intPi is an int variable, so even casting to float first, it truncates the decimal to 3.

Concept Snapshot

Type casting in C++ changes a value's type explicitly.
Syntax: (target_type) value or static_cast<target_type>(value).
Casting double to int truncates decimals.
Original variable stays unchanged.
Useful to convert types for operations or storage.

Full Transcript

This example shows type casting in C++. We start with a double variable pi holding 3.14. We cast it to int using (int)pi, which removes the decimal part and stores 3 in intPi. The original pi remains 3.14. The program returns intPi which is 3. This shows how casting changes the type and value representation explicitly.