---
id: c-structs
title: "C Structures (structs)"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["struct keyword", "dot syntax", "C 구조체"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.87
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["c", "programming-language", "w3schools", "structs"]
raw_sources: ["https://www.w3schools.com/c/c_structs.php"]
applied_in: []
github_commit: ""
---

# [[C Structures (structs)]]

## 🎯 한 줄 통찰 (One-line insight)
Directly assigning a string literal to a struct's `char[]` member (`s1.myString = "Some text";`) produces a compile ERROR ("assignment to expression with array type") — the exact same restriction from the Strings chapter (arrays can't be reassigned wholesale) applies inside structs too, requiring `strcpy()` UNLESS the assignment happens at declaration time using the comma-separated initializer syntax, which is the one place string literals ARE allowed directly. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Structure (`struct`)** — groups multiple MIXED-type variables ("members") into one unit, unlike arrays which require a single uniform type. [S1]
- **Declaration + variable creation** — the `struct Name {...};` block only defines the TEMPLATE; you must separately declare `struct Name variableName;` to create an actual instance. [S1]
- **Dot syntax (`.`)** — accesses/assigns individual members (`s1.myNum = 13;`). [S1]
- **String members require `strcpy()`** — direct assignment (`s1.myString = "text";`) fails to compile; use `strcpy(s1.myString, "text");` instead. [S1]
- **Initializer-list exception** — at DECLARATION time, `struct myStructure s1 = {13, 'B', "Some text"};` allows string literals directly, no `strcpy()` needed — values must be listed in the same order as the members were declared. [S1]
- **Struct-to-struct copy** — `s2 = s1;` copies ALL members at once, including string arrays, without needing `strcpy()` per-field. [S1]
- **Template reuse** — one struct definition (e.g. `Car`) can be instantiated repeatedly with different values (`car1`, `car2`, `car3`), avoiding separate ad-hoc variable sets per entity. [S1]

## 📖 세부 내용 (Details)
- The string-assignment error case: `s1.myString = "Some text"; // error: assignment to expression with array type`. [S1]
- The `strcpy()` fix: `strcpy(s1.myString, "Some text");`. [S1]
- Initializer-list shortcut bypassing `strcpy()`: `struct myStructure s1 = {13, 'B', "Some text"};`. [S1]
- Real-life template reuse: `struct Car { char brand[30]; char model[30]; int year; }; struct Car car1 = {"BMW", "X5", 1999}; struct Car car2 = {"Ford", "Mustang", 1969};`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **문자열 멤버 직접 대입 불가**: 구조체 안의 char 배열 멤버에도 배열 챕터와 동일한 제약이 적용되어 strcpy()가 필요하지만, 선언 시 초기화 리스트({...}) 문법에서는 예외적으로 문자열 리터럴을 직접 쓸 수 있다는 점이 확인됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
Car 구조체 하나로 BMW/Ford/Toyota 세 대의 서로 다른 자동차 정보를 저장하는 예제가 원문에서 직접 실전 활용 사례로 제시됨(하나의 템플릿, 여러 인스턴스). [S1]

## 💻 코드 패턴 (Code patterns)
One struct template reused for multiple distinct real-world entities (C):
```c
struct Car {
  char brand[30];
  char model[30];
  int year;
};
int main() {
  struct Car car1 = {"BMW", "X5", 1999};
  struct Car car2 = {"Ford", "Mustang", 1969};
  printf("%s %s %d\n", car1.brand, car1.model, car1.year);
  return 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:** 0.87
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[C Tutorial]]
- **관련 개념:** [[C Arrays RealLife]], [[C Strings Functions]], [[C Structs Nested]]
- **참조 맥락:** 구조체 섹션 첫 챕터 — 중첩 구조체(Structs Nested) 챕터로 이어짐.

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

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