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Pointers

Pointers. 황 강 욱 Next Generation Communication Networks Lab. Division of Applied Mathematics KAIST. Pointer. Pointer : Memory 주소 값을 저장하고 있는 변수 Pointer 의 자료형 : int, float, char 포인터가 저정하고 있는 메모리에 저장된 data type Pointer 의 선언 int *int_ptr; float *float_ptr; char *char_ptr;.

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Pointers

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  1. Pointers 황 강 욱 Next Generation Communication Networks Lab. Division of Applied Mathematics KAIST

  2. Pointer • Pointer : Memory 주소 값을 저장하고 있는 변수 • Pointer의 자료형 : int, float, char • 포인터가 저정하고 있는 메모리에 저장된 data type • Pointer의 선언 • int *int_ptr; • float *float_ptr; • char *char_ptr; Next Generation Communication Networks Lab.

  3. 변수의 주소값을 알려면? • int i; • int *i_ptr; • i_prt = & i; • cout << i_prt << endl; Next Generation Communication Networks Lab.

  4. a[0] a[1] a[2] a[3] a[4] a[5] 1차원 배열과 pointer • int a[6]; • 배열의 시작주소 : a 또는 &a[0] c.f. 배열의 이름이 그 배열의 시작주소를 나타냄. • pointer 연산 • a == &a[0] • a + i == &a[i] • *(a+i) == a[i] Next Generation Communication Networks Lab.

  5. 2차원 배열과 pointer • int a[2][2]; • a == a[0] == & a[0][0] • a[0] + 1 == & a[0][1] • a[0] + 2 == a[1] == & a[1][0] • a[0] + 3 == a[1]+1 == & a[1][1] • a + 1 == a[1] • *a[0] == a[0][0] • *a == a[0] • *a + 1 == a[1] • *(*a+1) == a[1][0] a a[0] a[0]+1 a+1 a[1] a[1]+1 a[0][0] a[0][1] a[1][0] a[1][1] Next Generation Communication Networks Lab.

  6. int *b[2]; // b[0]와 b[1] 두개의 int pointer 선언 • int (*c)[2]; // 2개의 원소를 갖는 int 배열의 pointer 선언 • 함수에서의 활용 • void function(int a[][2]) • void function(int (*a)[2]) Next Generation Communication Networks Lab.

  7. Pointers to pointers main() { int a; int * b; int ** c; //pointer to pointer a = 1; b = &a; c = &b; cout << a << endl; cout << b << endl; cout << *b << endl; cout << c << endl; cout << *c << endl; } a b c 0x100 1 0x520 0x100 0x520 0x700 Next Generation Communication Networks Lab.

  8. 함수의 포인터 int inc(int i) { return i+1;} int dec(int i) {return i-1;} main() { int i=1; int (*func)(int); func = inc; cout << func(1) << endl; //함수 포인터 사용 예 1 func = dec; cout << (*func)(2) << endl; //함수 포인터 사용 예 2 } 함수의 포인터 Next Generation Communication Networks Lab.

  9. 함수의 포인터 배열 enum {add, sub, multi, div}; int add(int a, int d) {return a+d;} int sub(int a, int d) {return a-d;} int multi(int a, int d) {return a*d;} int div(int a, int d) {return (a/d);} int (*func[4])(int, int) = {add, sub, multi, div}; main() { cout << (*func[add])(2,1) << “, “ << (*func[sub])(2,1); cout << (*func[multi])(2,1) << “, “ << (*func[div])(2,1); } Next Generation Communication Networks Lab.

  10. void pointer • void pointers are pointers that point to a value that has no type . • This allows void pointers to point to any data type, from an integer value or a float to a string of characters. Next Generation Communication Networks Lab.

  11. #include <iostream> void increase (void* data) { switch (sizeof(data)) { case sizeof(char) : (*((char*)data))++; break; case sizeof(int) : (*((int*)data))++; break; } } int main () { char a = 'x'; int b = 1602; increase (&a); increase (&b); cout << a << ", " << b; return 0; } y, 1603 Next Generation Communication Networks Lab.

  12. NULL Pointer • A null pointer is a regular pointer of any pointer type which has a special value that indicates that it is not pointing to any valid reference or memory address • int * p; p = NULL; // p has a null pointer value Next Generation Communication Networks Lab.

  13. pointers to classes main() class person { public: name[30]; phone[20]; }; person p_list[100]; person *list_ptr; list_ptr = p_list; strcpy(list_ptr->name,"aaa"); cout << list_ptr->name << endl; } Next Generation Communication Networks Lab.

  14. 실습 (Due Nov. 16) • 주어진 파일에서 사람이름과 전화번호를 입력받아 person 배열에 저장하고, 이름에 따른 사전식 순서대로 sorting하여 출력하는 프로그램을 작성하시오. (person class를 이용함) • 파일예 David Kim 111-1234 Tom Kim 123-9099 Jane Jung 190-0090 Brown Lee 123-1234 John Ahn 729-0987 • void sorting(person *a, person *b) Next Generation Communication Networks Lab.

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