Naming Variables

# Naming Variables

## Overview

The most important consideration in naming a variable is that the name fully and accurately describes the entity the variable represents.

**Core principle:** A variable and its name are essentially the same thing. The goodness or badness of a variable is largely determined by its name.

**Name quality = Design quality.** If you struggle to name something well, that's a warning sign about the design.

## When to Use

**Always use when:**
- Naming any variable, function, class, parameter, constant
- Reviewing code with unclear names
- Struggling to understand what a variable does

**Warning signs you need better names:**
- Variables named `x`, `x1`, `x2`, `temp`, `data`, `info`, `val`
- Can't remember what a variable does
- Need to search back to find variable's purpose
- Abbreviations that aren't obvious
- Names that could mean multiple things
- Struggling to name something (indicates design problem)

## Naming Principles

### 1. Describe What, Not How

**Problem-oriented** (what it represents) not **solution-oriented** (how it's implemented):

✅ **Good:** `employeeData`, `printerReady`, `totalRevenue`
❌ **Bad:** `inputRec`, `bitFlag`, `calcVal`

The bad names describe computing concepts (input, record, bit, calculation). Good names describe the problem domain (employee, printer, revenue).

### 2. Use Optimal Name Length

**Optimal: 10-16 characters average**
- Too short: doesn't convey meaning
- Too long: hard to type, obscures structure

| Too Long | Too Short | Just Right |
|----------|-----------|------------|
| `numberOfPeopleOnTheUsOlympicTeam` | `n`, `np`, `ntm` | `numTeamMembers`, `teamMemberCount` |
| `numberOfSeatsInTheStadium` | `n`, `ns`, `nsisd` | `numSeatsInStadium`, `seatCount` |
| `maximumNumberOfPointsInModernOlympics` | `m`, `mp`, `max` | `teamPointsMax`, `pointsRecord` |

**Exception:** Short names OK for very limited scope (loop index `i` in 3-line loop)

### 3. Scope Affects Name Length

- **Long scope (class, global):** Longer, more descriptive names
- **Short scope (loop variable, local):** Shorter acceptable
- **Very short scope (5-line loop):** `i`, `j` acceptable

Short name says: "I'm a scratch value with limited scope, don't look for me elsewhere"

### 4. State What Variable Represents

Effective technique: state in words what the variable represents. Often that statement IS the best name.

**Example:**
- "Running total of checks written to date" → `runningTotal` or `checkTotal`
- "Velocity of a bullet train" → `velocity`, `trainVelocity`, `velocityInMph`
- "Current date" → `currentDate`, `todaysDate`

### 5. Computed-Value Qualifiers at End

Put qualifiers like `Total`, `Sum`, `Average`, `Max`, `Min`, `Count` at the END:

✅ **Good:** `revenueTotal`, `expenseAverage`, `pointsMax`, `customerCount`
❌ **Bad:** `totalRevenue` mixed with `revenueTotal` (inconsistent)

**Why:**
- Most significant part (revenue, expense) at front, read first
- Symmetry: `revenueTotal`, `revenueAverage`, `revenueMax`
- Prevents confusion (`totalRevenue` vs `revenueTotal` - pick one convention)

**Exception:** `Num` is ambiguous
- At start = total: `numCustomers` (count of all customers)
- At end = index: `customerNum` (specific customer number)
- **Better:** Use `Count` for total, `Index` for specific: `customerCount`, `customerIndex`

### 6. Use Obvious Words

Don't be clever. Use the ordinary, obvious words:

✅ `currentDate`, `employeeName`, `accountBalance`
❌ `cd`, `empNm`, `acctBal`

Programmers sometimes overlook using ordinary words, which is often the easiest solution.

### 7. Be Specific, Not Gene