---
id: c-operators-logical
title: "C Logical Operators"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["&& || !", "logical AND OR NOT", "C 논리 연산자"]
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: ["c", "programming-language", "w3schools", "operators", "logical"]
raw_sources: ["https://www.w3schools.com/c/c_operators_logical.php"]
applied_in: []
github_commit: ""
---

# [[C Logical Operators]]

## 🎯 한 줄 통찰 (One-line insight)
The login-check example combines a comparison-like value (`isLoggedIn`) with its NEGATION (`!isAdmin`) inside a single `&&` expression (`isLoggedIn && !isAdmin` = "regular user") — showing that logical operators aren't just for combining two independent conditions, but are routinely used to express compound business rules like "authenticated AND NOT privileged" as one evaluable expression. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`&&` (AND)** — returns 1 only if BOTH operands are true. [S1]
- **`||` (OR)** — returns 1 if AT LEAST ONE operand is true. [S1]
- **`!` (NOT)** — reverses the result: 1 becomes 0, 0 becomes 1. [S1]
- **1 = true, 0 = false** — the same convention as Comparison Operators; logical operators combine these int-valued truth results. [S1]

## 📖 세부 내용 (Details)
- Login/permission check combining AND and NOT: `int isLoggedIn = 1; int isAdmin = 0; printf("Regular user: %d\n", isLoggedIn && !isAdmin); printf("Has access: %d\n", isLoggedIn || isAdmin); printf("Not logged in: %d\n", !isLoggedIn);` — outputs `1`, `1`, `0` respectively. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- 현재까지 발견된 모순 사항 없음 (No contradictions found in available sources).

## 🛠️ 적용 사례 (Applied in summary)
로그인 여부와 관리자 권한을 조합해 "일반 사용자인지", "접근 권한이 있는지"를 판단하는 예제가 원문에서 직접 실전 활용 사례로 제시됨(인증/인가 로직의 기초). [S1]

## 💻 코드 패턴 (Code patterns)
Combining AND and NOT to express a compound access-control rule (C):
```c
int isLoggedIn = 1;
int isAdmin = 0;
printf("Regular user: %d\n", isLoggedIn && !isAdmin); // 1
printf("Has access: %d\n", isLoggedIn || isAdmin);    // 1
printf("Not logged in: %d\n", !isLoggedIn);           // 0
```

## ✅ 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:** [[C Operators Comparison]], [[C Bitwise Operators]], [[C Conditions Logical]]
- **참조 맥락:** 논리 연산자 — 비트 연산자(Bitwise Operators) 챕터로 이어짐, 조건문의 논리 연산(Conditions Logical) 챕터와 직접 연결.

## 📚 출처 (Sources)
- [S1] W3Schools — C Logical Operators — https://www.w3schools.com/c/c_operators_logical.php

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