---
id: c-functions-pointers
title: "C Function Pointer"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["pointer to function", "function pointer array", "C 함수 포인터"]
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", "functions", "function-pointers"]
raw_sources: ["https://www.w3schools.com/c/c_functions_pointers.php"]
applied_in: []
github_commit: ""
---

# [[C Function Pointer]]

## 🎯 한 줄 통찰 (One-line insight)
A function's NAME already acts as a pointer to its own code, even before you declare any explicit function-pointer variable — `ptr = add;` and `ptr = &add;` are shown to be IDENTICAL, meaning `add` (bare, no parentheses) is already an address in the same sense `&myAge` was an address for a variable, and declaring `int (*ptr)(int, int)` just gives you a variable that can hold, reassign, and pass around that already-existing address. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Function pointer declaration** — `returnType (*pointerName)(paramType1, paramType2, ...);` (parentheses around `*pointerName` are required). [S1]
- **Assignment equivalence** — `ptr = add;` and `ptr = &add;` do the same thing, since a function's name is already its address. [S1]
- **Call equivalence** — `ptr(5, 3);` and `(*ptr)(5, 3);` both correctly call the pointed-to function. [S1]
- **Choosing behavior at RUNTIME** — unlike a normal function call (fixed at compile time), a function pointer lets the program decide WHICH function to run while it's already executing. [S1]
- **Function pointer array** — storing multiple function pointers in one array (`void (*operations[3])() = {add, subtract, multiply};`) enables selecting a function by INDEX, e.g. from user input, powering menus/calculators. [S1]

## 📖 세부 내용 (Details)
- Basic function pointer declaration, assignment, and call: `int add(int a, int b) { return a + b; } int (*ptr)(int, int) = add; int result = ptr(5, 3); // same as add(5,3)`. [S1]
- Passing a function pointer as an argument (a callback): `void greet(void (*func)()) { func(); } greet(greetMorning); greet(greetEvening);`. [S1]
- A calculator selecting among functions by user-entered index: `void (*operations[3])(int, int) = { add, subtract, multiply }; scanf("%d", &choice); operations[choice](x, y);`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **함수 이름은 이미 포인터**: ptr = add와 ptr = &add가 완전히 동일하게 작동한다는 점에서, 함수 이름 자체가 이미 메모리상 코드 시작 주소를 가리키는 포인터 역할을 하고 있음이 확인됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
사용자가 숫자를 입력해 덧셈/뺄셈/곱셈 중 하나를 선택하는 계산기 예제가 원문에서 직접 실전 활용 사례로 제시됨(함수 포인터 배열 + scanf 조합). [S1]

## 💻 코드 패턴 (Code patterns)
Selecting which function to run at runtime via a function pointer array indexed by user input (C):
```c
void add(int a, int b) { printf("Result: %d\n", a + b); }
void subtract(int a, int b) { printf("Result: %d\n", a - b); }
void multiply(int a, int b) { printf("Result: %d\n", a * b); }
int main() {
  int choice, x = 10, y = 5;
  void (*operations[3])(int, int) = { add, subtract, multiply };
  scanf("%d", &choice);
  if (choice >= 0 && choice < 3) {
    operations[choice](x, y);
  }
  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 Functions Recursion]], [[C Pointers]], [[C Functions Callback]]
- **참조 맥락:** 함수 포인터 — 콜백 함수(Functions Callback) 챕터로 이어짐.

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

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