---
id: cpp-function-structures
title: "C++ Pass Structures to a Function"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["pass by value struct", "pass by reference struct", "C++ 구조체를 함수로 전달"]
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: ["cpp", "programming-language", "w3schools", "functions", "structs"]
raw_sources: ["https://www.w3schools.com/cpp/cpp_function_structures.asp"]
applied_in: []
github_commit: ""
---

# [[CPP Pass Structures to a Function]]

## 🎯 한 줄 통찰 (One-line insight)
Passing a struct WITHOUT `&` gives the function a full COPY — mutating it inside the function leaves the caller's original untouched — while passing it WITH `&` gives the function the ORIGINAL, letting `c.year++;` permanently increment the caller's struct field, meaning the exact same `&` reference syntax from the Pass By Reference chapter extends naturally to entire structs, not just primitive types like `int`/`string`. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Pass by value (default)** — `void myFunction(Car c)` gives the function a COPY of the struct; modifying `c` inside the function does NOT affect the caller's original. [S1]
- **Pass by reference (`Car &c`)** — gives the function the ORIGINAL struct; modifications inside the function DO persist in the caller. [S1]
- **When to use reference** — to let the function change the struct's data, OR to avoid copying large structures (performance). [S1]

## 📖 세부 내용 (Details)
- Pass by value — original unaffected: `struct Car { string brand; int year; }; void myFunction(Car c) { cout << "Brand: " << c.brand << ", Year: " << c.year << "\n"; } Car myCar = {"Toyota", 2020}; myFunction(myCar); // myCar unchanged after this call`. [S1]
- Pass by reference — original mutated: `void updateYear(Car &c) { c.year++; } Car myCar = {"Toyota", 2020}; updateYear(myCar); cout << myCar.year; // 2021 — the original was incremented`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **값 전달과 참조 전달의 결과 차이**: & 없이 구조체를 전달하면 함수는 복사본을 받아 원본이 바뀌지 않지만, &를 붙이면 원본 자체를 받아 함수 안의 변경이 그대로 유지된다는 점이 year++ 예제로 직접 대비되어 증명됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
자동차 구조체의 연식(year)을 참조로 전달받아 함수 안에서 1씩 증가시키고 그 변경이 원본에 반영되는 updateYear() 예제가 원문에서 직접 실전 활용 사례로 제시됨. [S1]

## 💻 코드 패턴 (Code patterns)
Passing a struct by reference so the function can permanently modify it (C++):
```cpp
struct Car {
  string brand;
  int year;
};
void updateYear(Car &c) {
  c.year++;
}
int main() {
  Car myCar = {"Toyota", 2020};
  updateYear(myCar);
  cout << "The " << myCar.brand << " is now from year " << myCar.year << "."; // 2021
  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:** 0.86
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[C++ Tutorial]]
- **관련 개념:** [[CPP Function Reference]], [[CPP Functions Recursion]], [[CPP Structs]]
- **참조 맥락:** 구조체를 함수로 전달 — 재귀(Functions Recursion) 챕터로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — C++ Pass Structures to a Function — https://www.w3schools.com/cpp/cpp_function_structures.asp

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