---
id: c-constants
title: "C Constants"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["const keyword", "read-only variables", "C 상수"]
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", "constants"]
raw_sources: ["https://www.w3schools.com/c/c_constants.php"]
applied_in: []
github_commit: ""
---

# [[C Constants]]

## 🎯 한 줄 통찰 (One-line insight)
A `const` variable MUST be assigned a value at the moment of declaration — declaring it first and assigning later (`const int minutesPerHour; minutesPerHour = 60;`) is explicitly shown as an error — meaning `const` isn't just "can't change later," it also removes the two-step declare-then-assign pattern that ordinary variables freely support. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`const` keyword** — makes a variable unchangeable/read-only after its initial assignment. [S1]
- **Mandatory initialization** — a `const` variable must receive its value at declaration time; assigning it afterward is a compile error. [S1]
- **Uppercase naming convention** — while not required, C programmers commonly write constant names in uppercase (e.g. `BIRTHYEAR`) for readability. [S1]
- **Use case** — values unlikely to ever change during program execution (e.g. `minutesPerHour`, `monthsInYear`). [S1]

## 📖 세부 내용 (Details)
- Attempting reassignment fails: `const int myNum = 15; myNum = 10; // error: assignment of read-only variable 'myNum'`. [S1]
- Declare-without-assign fails: `const int minutesPerHour; minutesPerHour = 60; // error`. [S1]
- Uppercase convention: `const int BIRTHYEAR = 1980;`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **const는 선언과 동시에 초기화 필수**: 일반 변수처럼 먼저 선언만 하고 나중에 값을 대입하는 방식이 const에서는 컴파일 에러를 발생시킨다는 점이 명시적으로 확인됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 시간당 분(60), 연중 개월 수(12)처럼 절대 변하지 않는 값을 const로 선언하는 것이 실전 코드에서의 표준 활용이다. [S1]

## 💻 코드 패턴 (Code patterns)
Declaring constants that must be initialized at the point of declaration (C):
```c
const int minutesPerHour = 60;
const int monthsInYear = 12;
const int BIRTHYEAR = 1980;  // uppercase is a common naming convention
```

## ✅ 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 Data Types RealLife]], [[C Storage Classes]]
- **참조 맥락:** 상수 선언 — 저장 클래스(Storage Classes) 챕터로 이어짐.

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

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