对memory的操作总结

//============================================================================
// Name        : HelloWorld.cpp
// Author      : 
// Version     :
// Copyright   : Your copyright notice
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
#include <stdio.h>/* printf, scanf, NULL */
#include <string.h>
/* malloc example: random string generator*/
#include <stdlib.h>     /* malloc, free, rand */

using namespace std;

int main() {
    cout << "ffffssss!Hello World!!!" << endl; // prints !!!Hello World!!!
    printf("open success\n");
//malloc study
    int i, n;
    char * buffer;

    printf("How long do you want the string? ");
    scanf("%d", &i);

    buffer = (char*) malloc(i + 1);
    if (buffer == NULL)
        exit(1);

    for (n = 0; n < i; n++)
        buffer[n] = rand() % 26 + 'a';
    buffer[i] = '\0';

    printf("Random string: %s\n", buffer);
    free(buffer);
//calloc study
    int i1, m;
    int * pData;
    printf("Amount of numbers to be entered: ");
    scanf("%d", &i1);
    pData = (int*) calloc(i1, sizeof(int));
    if (pData == NULL)
        exit(1);
    for (m = 0; m < i1; m++) {
        printf("Enter number #%d: ", m + 1);
        scanf("%d", &pData[m]);
    }
    printf("You have entered: ");
    for (m = 0; m < i1; m++)
        printf("%d ", pData[m]);
    free(pData);

//realloc
    int input, n;
    int count = 0;
    int* numbers = NULL;
    int* more_numbers = NULL;

    do {
        printf("Enter an integer value (0 to end): ");
        scanf("%d", &input);
        count++;

        more_numbers = (int*) realloc(numbers, count * sizeof(int));

        if (more_numbers != NULL) {
            numbers = more_numbers;
            numbers[count - 1] = input;
        } else {
            free(numbers);
            puts("Error (re)allocating memory");
            exit(1);
        }
    } while (input != 0);

    printf("Numbers entered: ");
    for (n = 0; n < count; n++)
        printf("%d ", numbers[n]);
    free(numbers);

//memset
    //set int type
    int a[5];
    int num = 5 * sizeof(int);
    cout << num << "is num" << "\n";
//    memset(a,1,5*sizeof(int));
    //memset(a,1,num);
    memset(a, 1, 20);
    for (int i = 0; i < 5; i++)
        cout << a[i] << "";

    //set char type
    char str[] = "almost every programmer should know memset!";
    memset(str, '-', 6);
    puts(str);

    return 0;
}

malloc，calloc，realloc，memset学习