---
id: c-conditions-reallife
title: "C If ... Else Examples"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["real-life if else", "even or odd example", "C 조건문 실전 예제"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.83
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["c", "programming-language", "w3schools", "conditions", "real-life-example"]
raw_sources: ["https://www.w3schools.com/c/c_conditions_reallife.php"]
applied_in: []
github_commit: ""
---

# [[C If ... Else Examples]]

## 🎯 한 줄 통찰 (One-line insight)
The even/odd checker reuses the `%` modulus operator from the Arithmetic Operators chapter for a purpose that has nothing to do with "remainder after division" in the everyday sense — `myNum % 2 == 0` is the standard idiom for parity checking, showing that modulus's real-world utility often lies in binary classification (even/odd, every-Nth) rather than literal division-remainder arithmetic. [S1]

## 🧠 핵심 개념 (Core concepts)
- **This chapter is a compilation** — six worked real-life if/else scenarios, consolidating patterns from every prior Conditions sub-chapter (basic if/else, else-if chains, nested if, logical operators). [S1]
- **Door-code check** — a single `==` equality check gating access. [S1]
- **Positive/negative/zero classification** — a three-way `if`/`else if`/`else` chain covering all three number sign cases. [S1]
- **Even/odd via modulus** — `num % 2 == 0` is the standard parity-check idiom. [S1]
- **Temperature banding** — a three-tier `if`/`else if`/`else` chain (freezing/cool/warm) based on numeric thresholds. [S1]

## 📖 세부 내용 (Details)
- Door code check: `int doorCode = 1337; if (doorCode == 1337) { printf("Correct code.\nThe door is now open."); } else { printf("Wrong code.\nThe door remains closed."); }`. [S1]
- Positive/negative/zero: `int myNum = 10; if (myNum > 0) { printf("The value is a positive number."); } else if (myNum < 0) { printf("The value is a negative number."); } else { printf("The value is 0."); }`. [S1]
- Even/odd check: `int myNum = 5; if (myNum % 2 == 0) { printf("%d is even.\n", myNum); } else { printf("%d is odd.\n", myNum); }`. [S1]
- Temperature banding: `int temperature = 30; if (temperature < 0) { printf("It's freezing!\n"); } else if (temperature < 20) { printf("It's cool.\n"); } else { printf("It's warm.\n"); }`. [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
도어락 코드 확인, 숫자 부호 판별, 짝/홀수 판별, 온도 구간 분류, 접근 제어 등 6가지 실전 시나리오가 원문에서 직접 제시되며, 각각이 조건문 섹션 전체를 종합한 실전 활용 사례다. [S1]

## 💻 코드 패턴 (Code patterns)
The standard parity-check idiom using the modulus operator (C):
```c
int myNum = 5;
if (myNum % 2 == 0) {
  printf("%d is even.\n", myNum);
} else {
  printf("%d is odd.\n", myNum);
}
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.83
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[C Tutorial]]
- **관련 개념:** [[C Conditions Nested]], [[C Operators Arithmetic]], [[C Switch]]
- **참조 맥락:** 조건문 섹션 마지막 — switch 문(Switch) 섹션으로 이어짐.

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

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