Some Problem With My Program

Problem: I created a program for booking tickets. It works fine when its for single user. But when i make it for multi user, "user[100]". Funny characters starts to pop up when i key in the seats numbers. Example Smiling face, heart shape etc. When i open the source file user.txt those funny characters is printed as C in the file. Causing my program to be very unstable. Below is my code for booking.
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Code:

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int choice();
int i,m,n,row,column,x=5,y=5;

#define FILENAME "user.txt"

void show_main_menu();
void logo();
void book_ticket();
void edit_booking();
void cancel_booking();
void view_available();
void exitt();
void thank_you();
void look_up();

struct data
{
    char useless[1];
    char seat[5][10];
    char name[30];
    char nirc_number[10];
    char contact_number[10];
}user[100], data, sales_data[100], temp;

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Code:

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/*#############################################################################*/
/*                                Book Ticket Function                        */
/*#############################################################################*/
void book_ticket()
{                                       
   
    FILE *fptr;
    int quit=1;
    textcolor(YELLOW);
    fptr=fopen("user.txt","r");
    fread(&user[100],sizeof(user[100]),1,fptr);
    fclose(fptr);
    while(column!=99) 
    {
                system("cls");
                user[100].seat[row-1][column-1]='X';
               
                printf("\t\t\t \t      SCREEN          \n\n");
                printf("\t\t            1  2  3  4  5  6  7  8  9  10\n");
               
                printf("\n\t\t\t1  ");       
                for(i=0;i<10;i++)
                {
                    if(user[100].seat[0][i]>0)
                    printf(" %c ",user[100].seat[0][i]);
                }
                printf("\n\n");
               
                printf("\t\t\t2  ");
                for(i=0;i<10;i++)
                {if(user[100].seat[0][i]>0)
                    printf(" %c ",user[100].seat[1][i]);
                }
                printf("\n\n");
             
                printf("\t\t\t3  ");
                for(i=0;i<10;i++)
                {if(user[100].seat[0][i]>0)
                    printf(" %c ",user[100].seat[2][i]);
                }
                printf("\n\n");
               
                printf("\t\t\t4  ");
                for(i=0;i<10;i++)
                {if(user[100].seat[0][i]>0)
                    printf(" %c ",user[100].seat[3][i]);
                }
                printf("\n\n");
             
                printf("\t\t\t5  ");
                for(i=0;i<10;i++)
                {if(user[100].seat[0][i]>0)
                    printf(" %c ",user[100].seat[4][i]);
                }
               
                printf("\n\n\n\n\n");
                printf("\t\t\t  Enter Row Column(99,99 to quit): "); //choose to for 'X' 
                scanf("%d,%d",&row, &column);   
                if(row==99)
                        break;                 
    }
    clrscr();
    logo();
        printf("\n\n\n\n\t");
        gets(user[100].useless);
    printf("\n\tPlease Enter Your Name:");
        gets(user[100].name);
        printf("\n\tPlease Enter Owner IC Number:");
        gets(user[100].nirc_number);
        printf("\n\tPlease Enter Your Contact Number:");
        gets(user[100].contact_number);
        fopen("user.txt", "ab+");
    fwrite(&user[100],sizeof(user[100]),1,fptr);
    fclose(fptr);   
        printf("\n\n\n\n");
        printf("\n\tThank You For Providing Your Details");
        printf("\n\tPress Anykey To Continue");
        getch();
    thank_you();     
}

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If i was to change the "user[100]" to "user" it works fine. But i need it to be multi users. I have totally no idea how i can solve this problem. Appreciate help from members in this forum.
Can upload my whole program too if necessary. Heres the screenshot.
http://www.geocities.com/eradicate85/Program.JPG

Do you know how to use arrays?

In your code, user[100] represents one, and only one user. You can get access to the other 99 elements by changing the index eg. user[0], user[34], user[87]...

//Edit
I just woke up, so i didn't even notice that user[100] doesn't even belong to your array, only user[0] - user[99]
//

Your definition of user[100]; defines 100 users, but they are numbered 0 to 99. Therefore, user[100] itself does not exist. That's why you're getting weird stuff, you're reading memory you shouldn't.

You need to index into the users the same way you did with seat[][]. User number one would be user[0], the seat for user number 3 would be user[2].seat[0][i] or whatever.

Sorry for my insufficient programming knowledge, erm.. i don't quite get what you guys are saying. Would u guys mind giving me a small example or so to make me understand better?

Code:

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struct STUDENT
{
    char name[30];              // Student's name
    int  grade;                // Student's current grade
    int  test_scores[10];      // Student's test scores
} student[100];    // define 100 students, 0-99


// To print out the information for each student:

for (k=0; k < 100; k++)    // Set up loop for each student
{
    printf("%s  %2d  ", student[k].name, student[k].grade);
    for (j=0; j<10; j++)    // loop thru each test score
    {
        printf("%2d ", student[k].test_scores[j]);
    }
    printf("\n");
}

---

The outer loop references each student. The inner loop each test for the current student.

Code:

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/ *#################################################
############################*/
/*                                Book Ticket Function                        */
/ *#################################################
############################*/
void book_ticket()
{                                       
   
    FILE *fptr;
    int quit=1;
    textcolor(YELLOW);
    fptr=fopen("user.txt","r");
    fread(&user[i],sizeof(user[i]),1,fptr);
    fclose(fptr);
    while(column!=99) 
    {
                system("cls");
                user[i].seat[row-1][column-1]='X';
               
                printf("\t\t\t \t      SCREEN          \n\n");
                printf("\t\t            1  2  3  4  5  6  7  8  9  10\n");
               
                printf("\n\t\t\t1  ");       
                for(i=0;i<10;i++)
                {
                    if(user[i].seat[0][i]>0)
                    printf(" %c ",user[i].seat[0][i]);
                }
                printf("\n\n");
               
                printf("\t\t\t2  ");
                for(i=0;i<10;i++)
                {if(user[i].seat[0][i]>0)
                    printf(" %c ",user[i].seat[1][i]);
                }
                printf("\n\n");
             
                printf("\t\t\t3  ");
                for(i=0;i<10;i++)
                {if(user[i].seat[0][i]>0)
                    printf(" %c ",user[i].seat[2][i]);
                }
                printf("\n\n");
               
                printf("\t\t\t4  ");
                for(i=0;i<10;i++)
                {if(user[i].seat[0][i]>0)
                    printf(" %c ",user[i].seat[3][i]);
                }
                printf("\n\n");
             
                printf("\t\t\t5  ");
                for(i=0;i<10;i++)
                {if(user[i].seat[0][i]>0)
                    printf(" %c ",user[i].seat[4][i]);
                }
               
                printf("\n\n\n\n\n");
                printf("\t\t\t  Enter Row Column(99,99 to quit): "); //choose to for 'X' 
                scanf("%d,%d",&row, &column);   
                if(row==99)
                        break;                 
    }
    clrscr();
    logo();
        printf("\n\n\n\n\t");
        gets(user[j].useless);
    printf("\n\tPlease Enter Your Name:");
        gets(user[i].name);
        printf("\n\tPlease Enter Owner IC Number:");
        gets(user[i].nirc_number);
        printf("\n\tPlease Enter Your Contact Number:");
        gets(user[i].contact_number);
        fopen("user.txt", "ab+");
    fwrite(&user[i],sizeof(user[i]),1,fptr);
    fclose(fptr);   
        printf("\n\n\n\n");
        printf("\n\tThank You For Providing Your Details");
        printf("\n\tPress Anykey To Continue");
        getch();
    thank_you();     
}

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I edit it some but it still doesn't work. Whats wrong? I very bad at arrays.. sorry if i looks very stupid..