---
id: cpp-files
title: "C++ Files"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["fstream library", "ofstream ifstream", "C++ 파일 입출력"]
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", "files", "fstream"]
raw_sources: ["https://www.w3schools.com/cpp/cpp_files.asp"]
applied_in: []
github_commit: ""
---

# [[CPP Files]]

## 🎯 한 줄 통찰 (One-line insight)
C++ replaces C's SINGLE `FILE*` type + mode-string (`"r"`/`"w"`/`"a"`) approach with THREE distinct CLASSES — `ofstream` (write-only), `ifstream` (read-only), `fstream` (both) — and reuses the SAME `<<`/`getline()` idioms already learned for `cout`/`cin`, meaning file I/O in C++ isn't a separate API to learn but the SAME stream-object pattern applied to files instead of the console. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`<fstream>`** — the header required for file operations, used ALONGSIDE `<iostream>`. [S1]
- **`ofstream`** — creates and writes to files. [S1]
- **`ifstream`** — reads from files. [S1]
- **`fstream`** — combines both: create, read, AND write. [S1]
- **Writing via `<<`** — the SAME insertion operator used for `cout` writes directly to a file object (`MyFile << "text";`). [S1]
- **Reading via `getline()`** — the SAME function used for `cin` input reads a file line by line inside a `while` loop, which naturally stops when there are no more lines. [S1]
- **`.close()`** — closing the file is good practice, cleaning up unnecessary memory. [S1]

## 📖 세부 내용 (Details)
- Creating and writing a file: `ofstream MyFile("filename.txt"); MyFile << "Files can be tricky, but it is fun enough!"; MyFile.close();`. [S1]
- Reading a file line by line: `string myText; ifstream MyReadFile("filename.txt"); while (getline(MyReadFile, myText)) { cout << myText; } MyReadFile.close();`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **파일 입출력이 콘솔 입출력과 동일한 문법을 재사용함**: C가 fopen()에 모드 문자열("r"/"w"/"a")을 넘기는 단일 방식이었다면, C++는 ofstream/ifstream/fstream 세 클래스로 나누되 cout의 <<와 cin의 getline()을 그대로 파일에도 재사용한다는 점이 확인됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — getline()을 while 루프와 결합해 파일을 한 줄씩 읽는 패턴이 파일 전체를 순회하는 실전 표준 방식이다. [S1]

## 💻 코드 패턴 (Code patterns)
Reading a file line by line using getline() inside a while loop (C++):
```cpp
#include <fstream>
string myText;
ifstream MyReadFile("filename.txt");
while (getline(MyReadFile, myText)) {
  cout << myText;
}
MyReadFile.close();
```

## ✅ 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 Debugging]], [[CPP User Input]], [[CPP Data Structures]], [[C Files]]
- **참조 맥락:** 파일 섹션 유일 챕터이자 마지막 — 데이터 구조(STL, Data Structures) 섹션으로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — C++ Files — https://www.w3schools.com/cpp/cpp_files.asp

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