C語言分配動態記憶體常用函式：malloc/calloc/realloc/free
C++語言用new/delete：詳見memory.cpp
1.通過new運算子分配單個變數
資料型別* 指標變數 = new 資料型別(初值); int* p2 = new int;int* p3 = new int (100);
2.通過new運算子分配陣列 int* p4 = new int[5]; int* p5 = new int[5] {10, 20, 30};
資料型別* 指標變數 = new 資料型別[陣列長度] {元素初值, …};
3.對於單個變數用delete銷燬，而對於陣列用delete[]銷燬 delete[] p4;
4.定位分配
資料型別* 指標變數 = new(起始地址) 資料型別(初值);
起始地址所標記的記憶體應該事先分配好。
5.new在分配記憶體(malloc)之後還會呼叫建構函式，delete/delete[]在釋放記憶體(free)之前先呼叫解構函式。

// 堆記憶體的動態分配與釋放
#include <iostream>
#include <cstdlib>
#include <iomanip>
using namespace std;
int main (void) {
    int* p1 = (int*)malloc (sizeof (int));
    cout << *p1 << endl;
    free (p1);
//  free (p1);
    p1 = NULL;
//  *p1 = 100;
//  cout << *p1 << endl;
 

    int* p2 = new int;
    cout << *p2 << endl;
    delete p2;
//  delete p2;
    p2 = NULL;
    int* p3 = new int (100);
    cout << *p3 << endl;
    delete p3;
    p3 = NULL;
    int* p4 = new int[5];
    for (size_t i = 0; i < 5; i++)
        p4[i] = i;
    for (size_t i = 0
 
; i < 5; i++)
        cout << p4[i] << ' ';
    cout << endl;
    delete[] p4;
    p4 = NULL;
    int* p5 = new int[5] {10, 20, 30};
    for (size_t i = 0; i < 5; i++)
        cout << p5[i] << ' ';
    cout << endl;
    delete[] p5;
    p5 = NULL;
    int* p6 = (int*)malloc (
        sizeof (int) * 0xFFFFFFFF);
    if (! p6)
        perror ("malloc");
    else {
        free (p6);
        p6 = NULL;
    }
    /*
    int* p7 = NULL;
    try {
        p7 = new int[0xFFFFFFFF];
    }
    catch (exception& ex) {
        cout << ex.what () << endl;
        cout << "請擴大記憶體！" << endl;
        return -1;
    }
    delete[] p7;
    p7 = NULL;
    */
//  int (*p8)[4] =
//      (int (*)[4])malloc (3 * 4 * sizeof (int));
    int (*p8)[4] = new int[3][4];
    for (size_t i = 0; i < 3; i++)
        for (size_t j = 0; j < 4; j++)
            p8[i][j] = i * 4 + j;
    for (size_t i = 0; i < 3; i++) {
        for (size_t j = 0; j < 4; j++)
            cout << setw (4) << p8[i][j];
        cout << endl;
    }
//  free (p8);
    delete[] p8;
    p8 = NULL;
    char buf[4];
    int* p9 = new (buf) int;//資料型別* 指標變數 = new(起始地址) 資料型別(初值);
    *p9 = 0x12345678;
    printf ("%#x %#x %#x %#x\n", buf[0], buf[1],
        buf[2], buf[3]);
//  delete p9;
    return 0;
}

執行結果：
0
0
100
0 1 2 3 4
10 20 30 3 4
malloc: Cannot allocate memory
0 1 2 3
4 5 6 7
8 9 10 11
0x78 0x56 0x34 0x12