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I have a home assignment which says that I have to store information about a mansion in a binary file. On the first line of that file I have to keep information about how many floors there are in the building and how many apartments there are on a floor (size of two-dimensional array). And on the next lines I have to keep info about the apartments - a unique number for each apartment, number of rooms in that apartment, number of people living there, family name, date when the family moved in that apartment, monthly rent.

So, the question is: how should I store that information and how should I read it? If I use fread(buf, size, number_of_elements, FIlE *), how would I know the number of the elements? For example, how do I read a family name when I don't know it's lenght?

Thanks in advance!

PS. Thank you, claptrap! I tried to write the data first into the binary file but I got some error :(

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>

#define NAPARTMENTS 21
#define TAX_ADULT 3
#define TAX_KID 1
#define TAX_ELEVATOR 2
#define NFLOORS 7
#define NROOMS 3

void main()
{
    FILE *fp;
    int i, j;

    struct info_apartments
    {
        unsigned numApartment, numRooms, numAdults, numKids, rent;
        char family[30], date[10];
    };
    typedef struct info_apartments data;

    data apartments[7][3];

    for(i=0; i<NFLOORS; i++)
        for(j=0; j<NROOMS; j++)
        {
            apartments[i][j].numApartment=i*10+j+1;
            printf("\nEnter the number of the rooms: ");
            scanf("%d", apartments[i][j].numRooms);
            printf("\nEnter number of adults: ");
            scanf("%d", apartments[i][j].numAdults);
            printf("\nEnter number of kids: ");
            scanf("%d", apartments[i][j].numKids);
            printf("\nEnter family name: ");
            scanf("%s", apartments[i][j].family);
            printf("\nEnter date: ");
            scanf("%s", apartments[i][j].date);
            //first two floors don't pay for elevator
            if(i+1<3)
                apartments[i][j].rent=(TAX_ADULT*apartments[i][j].numAdults)+(TAX_KID*apartments[i][j].numKids);
            else
                apartments[i][j].rent=((TAX_ADULT+TAX_ELEVATOR)*apartments[i][j].numAdults)+((TAX_KID+TAX_ELEVATOR)*apartments[i][j].rent);
        }
    if((fp=fopen("myfile", "ab"))==NULL)
    {
        printf("Error");
        exit(1);
    }

    if((fwrite(apartments, sizeof(apartments), 1, fp))!=1)
    {
        printf("Error!\n");
        exit(1);
    }
}
4

2 に答える 2

1

まず、最後の「if」行を次のように変更する必要があると思います。

 if((fwrite(&apartments, sizeof(apartments), 1, fp))!=1)

&..を入れるのを忘れました

2番目...ファイルから読み取りたい場合は、fread関数で同じことを行います

 fread(&apartments, sizeof(apartments), 1, fp);

また、データを確認できるように印刷することもできます。

 printf("%s",apartments[i][j].family);

また

 puts(apartments[i][j].family);
于 2013-08-31T05:51:55.380 に答える
0

保存/取得する必要がある情報を保持する構造体を作成することを検討してください。ヘッダー構造体は次のようになります

typedef struct
{
  short floors;
  short apartments;
} header;

ファイルの他の部分に対してさらに構造体を作成します。

次に、ファイルから読み取る（書き込みから書き込み）ときは、次のようにします

header h;
fread( &h, sizeof(h), 1, fp );

ヘッダーの情報を使用して、ファイルの残りの部分を読み書きする方法を計算できます。ファイルの残りの部分については、他の構造体がありますが、解決するために残します。

于 2013-05-18T17:15:41.743 に答える