What is the difference between float and double?

float is 32-bit and less precise; double is 64-bit with higher precision, used for scientific calculations.

When should I use decimal in .NET?

Use decimal for financial or currency calculations where precision is critical.

decimal vs float vs double in .NET - Explained with Examples

💡 Concept Name

Decimal vs Float vs Double

📘 Quick Intro

In .NET, float, double, and decimal are used to represent real numbers. They differ in precision, memory usage, and intended use cases—especially when accuracy matters like in finance or scientific computing.

🧠 Analogy / Short Story

Think of float as a quick sketch (fast but rough), double as a digital photo (high quality), and decimal as a blueprint (extremely accurate and detailed). When money is involved, always go with the blueprint—decimal.

🔧 Technical Explanation

float: 32-bit single-precision, approx 6-9 digits
double: 64-bit double-precision, approx 15-17 digits
decimal: 128-bit precision, 28-29 digits—ideal for financial & monetary calculations
float and double are binary floating-point types; decimal uses base 10

🎯 Purpose & Use Case

✅ Use float for performance-sensitive graphics or gaming
✅ Use double for scientific calculations and mathematical models
✅ Use decimal for financial, billing, and currency operations

💻 Real Code Example

float f = 1f / 3f;
double d = 1.0 / 3.0;
decimal m = 1m / 3m;

Console.WriteLine($""Float: {f}"");
Console.WriteLine($""Double: {d}"");
Console.WriteLine($""Decimal: {m}"");

❓ Interview Q&A

Q1: Which type is most precise?
A: decimal

Q2: When should you use decimal?
A: In financial or monetary calculations

Q3: What’s the size of float?
A: 32-bit

Q4: What’s the precision of double?
A: 15–17 digits

Q5: Can float handle large numbers accurately?
A: No, it’s less precise

Q6: What suffix should be used for decimal literals?
A: m or M

Q7: Are float and double base-2 or base-10?
A: Base-2 (binary)

Q8: Which type is slower but more accurate?
A: decimal

Q9: Which is default for floating-point in C#?
A: double

Q10: Can rounding errors occur in float/double?
A: Yes, due to binary representation

📝 MCQs

Q1. Which type has the highest precision?

float
double
decimal
int

Q2. What is the size of a float in C#?

64-bit
16-bit
128-bit
32-bit

Q3. What is the default floating point type in C#?

float
decimal
double
int

Q4. Which type is best for currency calculations?

float
double
decimal
byte

Q5. What suffix is used for a decimal literal?

d
f
m
x

Q6. Which type is faster but less precise?

decimal
float
double
long

Q7. How many digits of precision does double provide?

6–9
10–12
28–29
15–17

Q8. Which type uses base-10 internally?

float
double
decimal
none

Q9. Which is suitable for scientific calculations?

decimal
float
double
short

Q10. Why does float cause rounding errors?

Compiler bug
Limited range
Binary representation of decimal fractions
Stack overflow

💡 Bonus Insight

When accuracy is critical, especially in financial applications, always use decimal. Avoid float/double for prices, taxes, or interest rates due to floating-point rounding issues.

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decimal vs float vs double in .NET