---
id: c-conditions
title: "C If ... Else"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["if statement", "lowercase if", "C 조건문"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.86
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["c", "programming-language", "w3schools", "conditions", "if-statement"]
raw_sources: ["https://www.w3schools.com/c/c_conditions.php"]
applied_in: []
github_commit: ""
---

# [[C If ... Else]]

## 🎯 한 줄 통찰 (One-line insight)
Case sensitivity isn't just a general C rule mentioned in passing — this chapter singles it out specifically for `if`, explicitly warning that `If` or `IF` will generate an error, meaning the keyword has zero tolerance for capitalization variants despite `if` being one of the most frequently typed words in any C program. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Six comparison conditions** — `<`, `<=`, `>`, `>=`, `==`, `!=`, familiar from mathematics. [S1]
- **Four conditional constructs** — `if` (run code if true), `else` (run if false), `else if` (test a new condition if the first is false), `switch` (many alternative code blocks). [S1]
- **Case-sensitive keyword** — `if` must be lowercase; `If`/`IF` produce an error. [S1]
- **Boolean-variable readability pattern** — storing a comparison's result in a `bool` variable before using it in `if` makes complex or reused conditions easier to read. [S1]

## 📖 세부 내용 (Details)
- Basic if with literal values: `if (20 > 18) { printf("20 is greater than 18"); }`. [S1]
- If with variables: `int x = 20; int y = 18; if (x > y) { printf("x is greater than y"); }`. [S1]
- Using a boolean variable to hold the condition: `bool isGreater = x > y; if (isGreater) { printf("x is greater than y"); }` (requires `<stdbool.h>`). [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **if는 반드시 소문자**: If나 IF처럼 대소문자를 다르게 쓰면 에러가 발생한다는 점이 명시적으로 경고됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 복잡하거나 재사용되는 조건을 bool 변수에 미리 담아두는 패턴이 가독성 있는 조건문 작성의 실전 관행이다. [S1]

## 💻 코드 패턴 (Code patterns)
Storing a condition in a readable boolean variable before using it in an if statement (C):
```c
int x = 20;
int y = 18;
bool isGreater = x > y;
if (isGreater) {
  printf("x is greater than y");
}
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.86
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[C Tutorial]]
- **관련 개념:** [[C Booleans RealLife]], [[C Conditions Else]]
- **참조 맥락:** 조건문 섹션 첫 챕터 — else 문(Conditions Else) 챕터로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — C If ... Else — https://www.w3schools.com/c/c_conditions.php

## 📝 변경 이력 (Change history)
- 2026-07-04: Initial draft synthesized from the W3Schools "C If ... Else" page (Astra wiki-curation, P-Reinforce v3.1 format).