2nd/10_Wiki/Dev/Topic_C/C_Switch.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
c-switch	C Switch	Programming_Language	draft	conceptual		switch case break keyword default keyword C switch 문		B	0.86	2026-07-04	2026-07-04			c programming-language w3schools switch	https://www.w3schools.com/c/c_switch.php

C Switch

🎯 한 줄 통찰 (One-line insight)

break isn't optional cleanup — without it, C would keep executing every subsequent case block regardless of whether it matches, since switch on its own only decides WHERE to jump in, not where to stop; the source frames break as actively saving execution time by "ignoring" the rest of the switch block once a match is handled, implying that omitting it (fall-through) is a real and easy-to-make mistake in C, unlike languages where each case implicitly breaks. [S1]

🧠 핵심 개념 (Core concepts)

• switch (expression) — evaluates the expression ONCE, then compares it against each case value to find a match. [S1]
• case x: — a candidate value to match against; its code block runs if the switch expression equals x. [S1]
• break — exits the switch block immediately once a matching case has been handled, preventing execution from continuing into subsequent cases. [S1]
• default: — optional; runs if no case matches; must be the LAST statement in the switch and does not need its own break. [S1]

📖 세부 내용 (Details)

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

⚖️ 모순 및 업데이트 (Contradictions & updates)

• break 생략 시 다음 case로 계속 진행됨: switch는 일치하는 case를 찾아 진입점만 결정할 뿐, break가 없으면 이후 모든 case의 코드가 계속 실행된다는 점(fall-through)이 암묵적으로 경고됨. [S1]
• default는 반드시 마지막에 위치: default 키워드는 switch 블록의 마지막 statement여야 하며 break가 필요 없다는 점이 명시적으로 확인됨. [S1]

🛠️ 적용 사례 (Applied in summary)

요일 번호(1-7)를 요일 이름으로 변환하는 예제와, 주말이 아닌 요일에 대해 default로 "주말이 기대된다"는 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):

int day = 4;
switch (day) {
  case 6:
    printf("Today is Saturday");
    break;
  case 7:
    printf("Today is Sunday");
    break;
  default:
    printf("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: 0.86
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: C Tutorial
• 관련 개념: C Conditions RealLife, C While Loop
• 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/c/c_switch.php

📝 변경 이력 (Change history)

• 2026-07-04: Initial draft synthesized from the W3Schools "C Switch" page (Astra wiki-curation, P-Reinforce v3.1 format).