---
id: cpp-switch
title: "C++ Switch"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["switch case", "break keyword", "default keyword", "C++ switch 문"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.85
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["cpp", "programming-language", "w3schools", "switch"]
raw_sources: ["https://www.w3schools.com/cpp/cpp_switch.asp"]
applied_in: []
github_commit: ""
---

# [[CPP Switch]]

## 🎯 한 줄 통찰 (One-line insight)
The syntax overview explicitly labels `break` and `default` as "optional" — a framing C's chapter never used — yet the same fall-through risk applies identically: without `break`, execution continues into subsequent cases regardless of match, meaning "optional" describes their SYNTACTIC status (the switch compiles without them) rather than their PRACTICAL necessity for correct behavior. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`switch (expression)`** — evaluates the expression ONCE, then compares it against each `case` value. [S1]
- **`case x:`** — a candidate value to match; its block runs if the switch expression equals `x`. [S1]
- **`break`** — exits the switch block once a match is handled; described as OPTIONAL syntactically, though omitting it causes execution to fall through into later cases. [S1]
- **`default:`** — runs if no case matches; also optional. [S1]

## 📖 세부 내용 (Details)
- Weekday-name lookup via switch: `int day = 4; switch (day) { case 1: cout << "Monday"; break; ... case 4: cout << "Thursday"; break; ... }` — outputs "Thursday" for day 4. [S1]
- Using default for unmatched cases: `int day = 4; switch (day) { case 6: cout << "Today is Saturday"; break; case 7: cout << "Today is Sunday"; break; default: cout << "Looking forward to the Weekend"; }` — day 4 matches neither case 6 nor 7, so default runs. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **break와 default는 "선택 사항"이지만 실질적으로는 거의 필수**: 문법적으로는 생략 가능하다고 명시되지만, break가 없으면 이후 case로 계속 실행이 이어지는(fall-through) 문제가 C 챕터와 동일하게 존재함이 확인됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
요일 번호(1-7)를 요일 이름으로 변환하는 예제와, 주말이 아닌 요일에 대해 default로 메시지를 출력하는 예제가 원문에서 직접 실전 활용 사례로 제시됨. [S1]

## 💻 코드 패턴 (Code patterns)
Using default to handle any value not matched by an explicit case (C++):
```cpp
int day = 4;
switch (day) {
  case 6:
    cout << "Today is Saturday";
    break;
  case 7:
    cout << "Today is Sunday";
    break;
  default:
    cout << "Looking forward to the Weekend";
}
// Outputs "Looking forward to the Weekend"
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.85
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[C++ Tutorial]]
- **관련 개념:** [[CPP Conditions RealLife]], [[CPP While Loop]], [[C Switch]]
- **참조 맥락:** switch 섹션 유일 챕터 — 반복문(Loops) 섹션의 while 루프(While Loop) 챕터로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — C++ Switch — https://www.w3schools.com/cpp/cpp_switch.asp

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