C# for Beginners. Lessons 1: VARIABLES part 3
- Pavel Zosim
- 2 hours ago
- 2 min read
decimal ★ Money & Financial Calculations ★
Beginner explanation: The MOST precise decimal type, designed specifically for money and financial calculations. Has ~28-29 digits of precision and avoids the rounding errors that plague float/double. ALWAYS use decimal for currency, prices, and financial data. Much slower than float/double, so NEVER use in game loops or real-time calculations. Requires 'm' or 'M' suffix!
📊 Technical Specs:
Size: 16 bytes (128 bits)
Precision: ~28-29 significant digits
Range: ±1.0 × 10⁻²⁸ to ±7.9228 × 10²⁸
Default Value: 0.0m
⚡ Performance Notes:
❌ VERY SLOW - 10-100x slower than float/double
❌ No hardware acceleration (software-emulated)
❌ Uses 4x memory of float (16 vs 4 bytes)
✅ EXACT - no rounding errors for decimal values
✅ Perfect for financial calculations
💡 NEVER use in Update()/FixedUpdate() - too slow!
💡 Use ONLY for money, prices, currency
When to use decimal:
✅ Money/Currency (prices, costs, balances)
✅ Financial calculations (interest, tax, exchange rates)
✅ Accounting/billing systems
✅ Shop UI (display prices)
✅ Any calculation where exact decimal precision is legally required
❌ NEVER in game loops (Update, FixedUpdate)
❌ NEVER for positions, physics, transforms
❌ NEVER for real-time calculations
❌ Don't use if float/double are sufficient
💻 Syntax & Declaration:
🎮 Practical Use Cases:
⚠️ Common Pitfalls:
💡 Pro Tips:
char - Single Character
Beginner explanation: Stores a single character like 'A', '5', '@', or '中'. Uses single quotes, not double quotes! Internally it's just a number (0-65535) representing a Unicode character. Perfect for keyboard input, single letters, or text parsing.
📊 Technical Specs:
Size: 2 bytes (16 bits)
Range: '\u0000' to '\uffff' (0 to 65,535 - Unicode characters)
Default Value: '\0' (null character)
⚡ Performance Notes:
✅ Fast (just a 16-bit integer internally)
✅ 2 bytes (same as ushort)
✅ Good for menu systems, keyboard input
💡 String is usually more practical for text
💡 Use char for single-character operations only
When to use char:
✅ Single character storage
✅ Keyboard input (single key)
✅ Menu options (A, B, C, D)
✅ Character-by-character text parsing
✅ Grades, ratings (A, B, C)
✅ Direction indicators (N, S, E, W)
❌ Don't use for multi-character text (use string)
❌ Emojis need string (surrogate pairs)
💻 Syntax & Declaration:
🎮 Practical Use Cases:
⚠️ Common Pitfalls:
💡 Pro Tips:
💻 Syntax & Declaration:
🎮 Practical Use Cases:
⚠️ Common Pitfalls:
💡 Pro Tips:
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