Console C Program stopped working dev c++ - c

Question

I was practicing array of structure. I made the following program and there were no compiling errors.But when i try to run it(I guess these errors are called runtime errors?),it stops working just after accepting the roll number. I wonder what wrong i did.
I use Dev c++ and gcc compiler.
Here's the code:
#include<stdio.h>
struct student{
char Fname[];
char Lname[];
int reg_no;
int Class;
char sec;
};
void enterinfo(student *,int);
void Display(student *,int);
int main()
{
int i;
printf("\t\t\t Enter student's information\n\n\n\n");
printf("How many students are there in you're school: ");
scanf("%d",&i);
student ob[i],*ptr;
ptr=ob;
enterinfo(ptr,i);
Display(ptr,i);
}
void enterinfo(student *e,int y)
{
char CONT='y';
for (int j=0;j<y && (CONT=='y' || CONT=='Y');j++)
{
printf("Enter Students First Name: ");
scanf("%s",e->Fname);
printf("Enter Students Last Name: ");
scanf("%s",e->Lname);
printf("Enter Roll number: ");
scanf("%d",e->reg_no);
printf("Enter class: ");
scanf("%d",e->Class);
printf("Enter Section: ");
scanf("%d",e->sec);
printf("\n\n\n\n Do you want to enter more? : ");
scanf("%c",&CONT);
}
}
void Display(student *e,int y)
{
char CONT='y';
for (int j=0;j<y;j++)
{
printf("Students name : %s %s",e->Fname,e->Lname);
printf("Enter Roll number: %d",e->reg_no);
printf("class: %d",e->Class);
printf("Enter Section: %d",e->sec);
}
}

Answer 1

I've made the following changes to your code and it started working for me:
char Fname[]; --> char Fname[100];
char Lname[]; --> char Lname[100];
char sec; --> int sec; This is needed for scanf.
scanf("%d",e->reg_no); --> scanf("%d",&e->reg_no);
scanf("%d",e->Class); --> scanf("%d",&e->Class);
scanf("%d",e->sec); --> scanf("%d",&e->sec);
adding \n to the end of printf strings in Display
Please note that scanf("%s", ...) is insecure and it can cause a crash the input string is longer than the array size you're reading it to, i.e. if the user types a name of at least 100 bytes.
Please note that you should always check the return value of scanf, and abort early on error (i.e. if it doesn't return 1 in your case).
Please note that in C++ the istream methods (http://en.cppreference.com/w/cpp/header/istream) provide a safer way to read the input.

Answer 2

Here:
scanf("%d",e->reg_no);
you should insert a '&' symbol before e->reg_no. But I can see many other problems once you solve this...

Answer 3

You can use below code, it will run on both linux & windows. Your program halts because of:
scanf("%d",&e->reg_no);
printf("Enter class: ");
scanf("%d",&e->Class);
printf("Enter Section: ");
scanf("%d",&e->sec);
you did not use & which is must for int, char, float data types as it is used as reference of the variable.
#include
struct student{
char Fname[30];
char Lname[30];
int reg_no;
int Class;
char sec[5];
};
void enterinfo(student *,int);
void Display(student *,int);
int main()
{
int i;
printf("\t\t\t Enter student's information\n\n\n\n");
printf("How many students are there in you're school: ");
scanf("%d",&i);
student * ob = new student[i];
enterinfo(ob,i);
Display(ob,i);
}
void enterinfo(student *e,int y)
{
char CONT='y';
for (int j=0;jFname);
printf("Enter Students Last Name: ");
scanf("%s",e->Lname);
printf("Enter Roll number: ");
scanf("%d",&e->reg_no);
printf("Enter class: ");
scanf("%d",&e->Class);
printf("Enter Section: ");
scanf("%s",e->sec);
getchar();//to eat newline/ enter char of previous statement
printf("\n\n\n\n Do you want to enter more? : ");
scanf("%c",&CONT);
}
}
void Display(student *e,int y)
{
for (int j=0;jFname,e->Lname);
printf("\nEnter Roll number: %d",e->reg_no);
printf("\nclass: %d",e->Class);
printf("\nEnter Section: %s\n",e->sec);
}
}