---
id: c-functions
title: "C Functions"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["void function", "function call", "C 함수"]
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: ["c", "programming-language", "w3schools", "functions"]
raw_sources: ["https://www.w3schools.com/c/c_functions.php"]
applied_in: []
github_commit: ""
---

# [[C Functions]]

## 🎯 한 줄 통찰 (One-line insight)
The source reveals that `main()` and `printf()` — the two things every C beginner types on day one — are ALREADY functions, meaning the concept being "introduced" in this chapter isn't new at all; the learner has been using functions the entire tutorial without a name for it, and this chapter is really just formalizing vocabulary for a pattern already internalized. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Function** — a block of code that only runs when explicitly CALLED, not automatically at declaration time. [S1]
- **`void` return type** — indicates the function returns no value (covered in more depth in the Parameters chapter). [S1]
- **Declaration vs. execution timing** — declaring a function only "saves it for later use"; nothing inside runs until it's called. [S1]
- **Repeatable calls** — the same function can be called multiple times, each execution independent. [S1]
- **Code reuse motivation** — "define the code once, and use it many times" is the core justification for functions. [S1]

## 📖 세부 내용 (Details)
- Calling the same function three times: `void myFunction() { printf("I just got executed!"); } int main() { myFunction(); myFunction(); myFunction(); return 0; }` — prints the message three times. [S1]
- A function performing a fixed calculation: `void calculateSum() { int x = 5; int y = 10; int sum = x + y; printf("The sum of x + y is: %d", sum); }` — explicitly noted as LIMITED since x/y are hardcoded, motivating the next chapter's parameters. [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — main()과 printf() 자체가 이미 함수라는 사실을 상기시키는 것이 이 챕터의 핵심 실전 통찰이다. [S1]

## 💻 코드 패턴 (Code patterns)
Calling the same function multiple times (C):
```c
void myFunction() {
  printf("I just got executed!");
}
int main() {
  myFunction();
  myFunction();
  myFunction();
  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:** [[C Memory RealLife]], [[C Functions Decl]]
- **참조 맥락:** 함수 섹션 첫 챕터 — 함수 선언과 정의(Functions Decl) 챕터로 이어짐.

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

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