in files

#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
#include<string.h>
#define space "\t \t \t"
typedef struct File2
{
    void *portfolio;
    void *watchlist;
    void *account;
    void *transaction histroy;
} user_t;
void userpage(char *users);
void userpage(char *users)
{
    int max=5,select=1;
    while(1)
    {
    system("cls");
    system("color 07");

    }
}
int main()
{
    system("color 04");
    printf("WELCOME\n");
    printf("  TO    \n");
    printf("  HELIX  \n");
    printf("Press any Key\n");
    _getch();
    char users[100];
    if(Main_page(users)==0)
    {
        userpage(users);
    }
    else
    {
        printf("\nThank you for visiting\n");
    }
    return 0;
}
int Main_page(char *users)
{
    FILE *fp;
    char choice,x;
    char username[100];
    char password[100];
    int i=0;
main_sec:
    system("cls");
    while(1)
    {
        printf("Helix\n");
        printf("1)login\n");
        printf("2)signup\n");
        printf("3)exit");
        choice=_getch();
        if(choice== 49 || choice ==50 ||choice==51)
            break;
        else
        {
            printf("Enter valid choice\n");
        }
    }
    if(choice==49)
    {
        char x,*tempstr;
        char accountsDB[100];
        system("cls");
        printf("Login \n");
        printf("Username:");
        scanf("%s",username);
        printf("\n");
        i=0;
        while(username[i] != '\0')
        {
            users[i] = username[i];
            i++;
        }
        users[i] = '\0';
        i=0;
        printf("Password:");
        while ((x = _getch()) != '\r')
        {
            printf("*");
            password[i++] = x;
        }
        password[i] = '\0';
        i = 0;
        strcat(username, password);
        fp = fopen("PROJECT_DATA_FILE.txt","r");
        while((x = fgetc(fp)) != EOF)
        {
            accountsDB[i++] = x;
        }
        accountsDB[i] = '\0';
        fclose(fp);
        if(NULL == strstr(accountsDB, username))
        {
            printf("\n\n"space space"*Username or password is wrong");
            _getch();
            goto main_sec;
        }
        else
        {
            tempstr = strstr(accountsDB, username);
        }
        i=0;
        while(username[i]!='\0')
        {
            if(username[i]!=tempstr[i])
                break;

            i++;
        }
        if(i==strlen(username))
        {
            return 0;
        }
        else
        {
            printf("\n\n*Username or password is wrong");
            _getch();
            goto main_sec;
        }
    }
    if(choice ==50)
    {
        system("cls");
        printf("Signup\n");
        printf("Username:");
        scanf("%s",username);
        i=0;
        while((x = username[i]) != '\0')
        {
            if(x == '|' || x == '#' || x == '$')
            {
                printf("\n*Username must not contain special characters like |, #, $ etc.");
                _getch();
                goto main_sec;
            }
            i++;
        }
        char accountsDB[100];
        fp = fopen("PROJECT_DATA_FILE.txt","r");
        i = 0;
        while((x = fgetc(fp)) != EOF)
        {
            accountsDB[i++] = x;
        }
        fclose(fp);
        char temp_pass[100];
        if(NULL == strstr(accountsDB, username))
        {
            i=0;
            printf("Password:");
            while ((x = _getch()) != '\r')
            {
                printf("*");
                password[i++] = x;
            }
            password[i] = '\0';
            printf("\nRe-Enter password:");
            i = 0;
            while((x = _getch()) != '\r')
            {
                printf("*");
                temp_pass[i++] = x;
            }
            temp_pass[i]='\0';
            if(strcmp(temp_pass,password)==0)
            {
                i = 0;
                fp = fopen("PROJECT_DATA_FILE.txt","a");
                fputc('|',fp);
                while((x = username[i]) != '\0')
                {
                    fputc(x,fp);
                    i++;
                }
                i = 0;
                while((x = password[i]) != '\0')
                {
                    fputc(x,fp);
                    i++;
                }
                fputc('$', fp);
                fputc('1', fp);
                fputc('#', fp);
                fputc('1', fp);
                fclose(fp);
                printf("\n\nSign up successful");
                _getch();
                goto main_sec;
            }
            else
            {
                printf("\n\n*Passwords do not match, try again");
                _getch();
                goto main_sec;
            }
        }
        else
        {
            printf("\n*Username is already taken");
            _getch();
            goto main_sec;
        }
    }
    if(choice==51)
    {
        fclose(fp);
        return 1;
    }
}