---
id: c-while-loop
title: "C While Loop"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["while statement", "zero-iteration loop", "C while 반복문"]
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", "loops", "while"]
raw_sources: ["https://www.w3schools.com/c/c_while_loop.php"]
applied_in: []
github_commit: ""
---

# [[C While Loop]]

## 🎯 한 줄 통찰 (One-line insight)
A `while` loop can run ZERO times — if its condition is already false the very first time it's checked (e.g. `int i = 10; while (i < 5) {...}`), the body never executes at all, not even once — a behavior the source explicitly contrasts against the upcoming do/while chapter, which guarantees at least one execution regardless of the initial condition. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`while (condition) { ... }`** — repeats the block as long as the condition remains true, checked BEFORE each iteration (including the first). [S1]
- **Zero-iteration possibility** — if the condition is false from the start, the loop body never runs at all. [S1]
- **Mandatory condition-variable update** — forgetting to change the loop-controlling variable inside the body (e.g. omitting `i++`) causes an infinite loop. [S1]
- **`i` as a counter convention** — the source explains `i` is traditionally used because it's short and stands for "index"/"iterator," not an arbitrary choice. [S1]

## 📖 세부 내용 (Details)
- Basic counting loop: `int i = 0; while (i < 5) { printf("%d\n", i); i++; }`. [S1]
- Countdown loop: `int countdown = 3; while (countdown > 0) { printf("%d\n", countdown); countdown--; } printf("Happy New Year!!\n");`. [S1]
- Zero-iteration case: `int i = 10; while (i < 5) { printf("This will never be printed\n"); i++; }` — body never executes since the condition is false immediately. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **조건이 처음부터 거짓이면 while 루프는 한 번도 실행 안 됨**: do/while 루프(다음 챕터)와 달리 일반 while 루프는 시작부터 조건이 거짓이면 본문이 단 한 번도 실행되지 않는다는 점이 명시적으로 대비됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
카운트다운 후 "Happy New Year!!"를 출력하는 예제가 원문에서 직접 실전 활용 사례로 제시됨. [S1]

## 💻 코드 패턴 (Code patterns)
A while loop that never executes because its condition is false from the start (C):
```c
int i = 10;
while (i < 5) {
  printf("This will never be printed\n");
  i++;
}
```

## ✅ 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 Switch]], [[C While Loop RealLife]], [[C Do While Loop]]
- **참조 맥락:** 반복문 섹션 첫 챕터 — while 루프 실전 예제(While Loop RealLife) 챕터로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — C While Loop — https://www.w3schools.com/c/c_while_loop.php

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