Struktur data (alokasi memory)
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Pointer implements memory allocation in C++. Pointers store the address of a memory location rather than the data itself. Pointers allow indirect access to objects in memory and can be used to access data pointed to by the pointer through dereferencing. Pointer variables must be initialized with a memory address before dereferencing to access the data stored at that address. Passing arguments by value, reference, or pointer results in different behavior when modifying the arguments within the called function.
Struktur data (alokasi memory)
- 1. Pointer Implementasi pointer dalam pengalokasian memori * Struktur Data /3sks/Semester II (KELAS MALAM) Tahun Akademik 2012 - 2013 @Maret 2013 – by M. Mahaputra Hidayat, S.Kom *dirangkum dari berbagai sumber dan ITS “program = algorithm + data structure”
- 2. Struktur Data 2 * Kerjakan soal no 2.a Apa ya pointer itu ? • Pointer tidak menampung data • Pointer menampung alamat dari sel memori lain yang menampung nilai data yang dituju
- 8. Struktur Data 8 * : : Tambahkan 10 ke p : : : Tambahkan 10 ke data yang alamatnya tersimpan di p : p = 200 ?? : : 560 1000 1001 200 : : 1000 1001 200 : : p = 210 ?? : : 550 1000 1001 200 : : p = 200 ?? : : 550
- 9. 9 * : (&ptr) 1500 (&x) 1100 (&y) 1104 : : ptr = 1100 30 : 35 *ptr += 10; 35 30 ptr x y int *ptr; int x=25; Int y=30; : (&ptr) 1500 (&x) 1100 (&y) 1104 : : ptr = ? 30 : 25 25 30 ptr x y ptr = &x; : (&ptr) 1500 (&x) 1100 (&y) 1104 : : ptr = 1100 30 : 25 25 30 ptr x y
- 10. 10 * ... ... MEMORY 0 1 2 3 4 5 81345 81346 81347 Address int foo; int *x; foo = 123; x = &foo; foo x 123 3 menyediakan akses tidak langsung ke suatu obyek obyek untuk mengakses obyek lain dapat mengakses data yang ditunjuk oleh pointer dereferencing pointer
- 11. 11 * pointer harus memiliki nilai sebelum mengakses data yang ditunjuk (dereferenced ) int *x; *x=3; int foo; int *x; x = &foo; *x=3; &foo = alamat dari foo
- 12. 12 * int *intPtr; intPtr = new int; *intPtr = 6837; delete intPtr; int otherVal = 5; intPtr = &otherVal; inisialisasi pointer alokasi memory address set isi dari pointer merubah intPtr ke lokasi memory address lain 6837*intPtr 0x0050intPtr 5*intPtr 0x0054intPtr otherVal &otherVal membuang alokasi memory address
- 13. 13 * *ptr = 10; - nilai x berubah - nilai pointer ptr tetap
- 14. 14 * int x = 5; int y = 7; int *ptr = &x; // LEGAL int *ptr = &x; // ILLEGAL: x belum dideklarasikan int x = 5; int y = 7; int x = 5; int y = 7; int *ptr = x; // ILLEGAL: x bukan memory address int x = 5; int y = 7; int *ptr; // LEGAL: ptr belum diinisialisasi
- 15. 15 * #include <iostream> using namespace std; … … … int main(){ int Boys = 3, Girls = 5; void PassByValue(int males, int females); void Reference(int &m, int &f); void Pointers(int *u, int *v); cout << "At startup, within main()"; cout << "ntBoys = " << Boys; cout << "ntGirls = " << Girls; cout << "nPassing arguments by value = Copy"; PassByValue(Boys, Girls); cout << "nAfter calling PassByValue(), within main()"; cout << "ntBoys = " << Boys; cout << "ntGirls = " << Girls; … … … At startup, within main() Boys = 3 Girls = 5
- 16. 16 * … … … cout << "nPassing arguments by reference"; Reference(Boys, Girls); cout << "nAfter calling Reference(), within main()"; cout << "ntBoys = " << Boys; cout << "ntGirls = " << Girls; cout << "nPassing arguments pointers"; Pointers(&Boys, &Girls); cout << "nAfter calling Pointers(), within main()"; cout << "ntBoys = " << Boys; cout << "ntGirls = " << Girls; cout << "n"; system("PAUSE"); return 0; }
- 17. 17 * #include <iostream> using namespace std; void PassByValue(int b, int g){ b += 3, g += 4; cout << "nWithin PassByValue(), now"; cout << "ntBoys = " << b; cout << "ntGirls = " << g; } void Reference(int &b, int &g){ b += 3, g += 4; cout << "nWithin Reference(), now"; cout << "ntBoys = " << b; cout << "ntGirls = " << g; } void Pointers(int *b, int *g){ *b += 3, *g += 4; cout << "nWithin Pointers(), now"; cout << "ntBoys = " << *b; cout << "ntGirls = " << *g; } int main(){ … … … Passing arguments by value = Copy Within PassByValue(), now Boys = 6 Girls = 9 After calling PassByValue(), within main() Boys = 3 Girls = 5 Passing arguments by reference Within Reference(), now Boys = 6 Girls = 9 After calling Reference(), within main() Boys = 6 Girls = 9 Passing arguments pointers Within Pointers(), now Boys = 9 Girls = 13 After calling Pointers(), within main() Boys = 9 Girls = 13 At startup, within main() Boys = 3 Girls = 5 PassByValue(Boys, Girls); Pointers(&Boys, &Girls); Reference(Boys, Girls);
- 19. *Tugas Dikumpulkan paling lambat tanggal 11 Maret 2013, pukul 24.00 wib via email saya, format pdf sertakan foto anda disebelah nama. 1. Jelaskan (tracing) dan tentukan output dari Soal 1 dan Soal 2 ! 2. Jelaskan perbedaan antara Soal 3 dan Soal 4, kemudian tentukan output dari kedua soal tersebut !
- 20. Ballighu’ anniy walau aayatun . . . Sebarkanlah ilmu walau satu ayat . . . Thank’s for your attention, Surabaya, 05 Maret 2013