Program doesnt show the things I want it to show - arrays

Question

I am currently trying to write a program in which when the user selects "1" It will ask him the number of students.It will then create a dynamic array and store all of their information in there.However I am running into the problem where when I try to print the information of the students my program just spews out numbers and letters.Here is the program:
#include <stdio.h>
#include <stdlib.h>
typedef struct student{
int id;
char name[50];
char surname[50];
int semester;
float grade;
}student;
int main()
{
int x,std,i;
x=0;
student** info;
while (x!=8)
{
printf("1. Initialize student list\n2. Add a student record\n3. Delete a student record\n4. Display a student record by student surname\n5. Display students passed\n6. Display students failed\n7. Display all student records\n8. Exit");
printf("\nYour choice: ");
scanf("%d",&x);
if (x==1)
{
printf("How many new students? ");
scanf("%d",&std);
struct student come[std];
struct student *ptr = NULL;
ptr=come;
info = (student**)malloc(std*sizeof(student*));
for(i = 0; i < std; i++){
printf("Enter detail of student #%d\n", (i + 1));
ptr->id=i+1;
printf("Enter first name: ");
scanf("%s", ptr->name);
printf("Enter last name: ");
scanf("%s", ptr->surname);
printf("Enter semester: ");
scanf("%d", &ptr->semester);
printf("Enter grade: ");
scanf("%f", &ptr->grade);
ptr++;
}
}
else if (x==2)
{
/* code */
}
else if (x==3)
{
/* code */
}
else if (x==4)
{
/* code */
}
else if (x==5)
{
/* code */
}
else if (x==6)
{
}
else if (x==7)
{
struct student come[std];
struct student *ptr = NULL;
ptr=come;
for(i = 0; i < std; i++){
printf("%d", ptr->id);
printf("%s", ptr->name);
printf("%s", ptr->surname);
printf("%d", ptr->semester);
printf("%f", ptr->grade);
printf("\nn");
ptr++;
}
}
}
At first I used come[i].grade for all of them (name,id,etc) but it would return something along the lines of 19845241814DNva1280.000000 . Then I added the "&" before it but it gave me 6422088oIv4DNva64221920.000000. The last thing i tried is going with ptr->id but no luck.It just returned to me 19845241814DNv`a1280.000000. The same thing as the first.

Answer 1

The problem is how you use the pointers. There is no necessary use of a pointer to pointer.
#include <stdio.h>
#include <stdlib.h>
typedef struct student{
int id;
char name[50];
char surname[50];
int semester;
float grade;
}student;
int main()
{
int x,std,i;
x=0;
struct student *ptr = NULL;
while (x!=8)
{
printf("1. Initialize student list\n2. Add a student record\n3. Delete a student record\n4. Display a student record by student surname\n5. Display students passed\n6. Display students failed\n7. Display all student records\n8. Exit");
printf("\nYour choice: ");
scanf("%d",&x);
if (x==1)
{
printf("How many new students? ");
scanf("%d",&std);
ptr = (student*)malloc(std*sizeof(student));
for(i = 0; i < std; i++){
printf("Enter detail of student #%d\n", (i + 1));
ptr[i].id=i+1;
printf("Enter first name: ");
scanf("%s", ptr[i].name);
printf("Enter last name: ");
scanf("%s", ptr[i].surname);
printf("Enter semester: ");
scanf("%d", &ptr[i].semester);
printf("Enter grade: ");
scanf("%f", &ptr[i].grade);
}
}
else if (x==2)
{
/* code */
}
else if (x==3)
{
/* code */
}
else if (x==4)
{
/* code */
}
else if (x==5)
{
/* code */
}
else if (x==6)
{
}
else if (x==7)
{
for(i = 0; i < std; i++){
printf("%d", ptr[i].id);
printf("%s", ptr[i].name);
printf("%s", ptr[i].surname);
printf("%d", ptr[i].semester);
printf("%f", ptr[i].grade);
printf("\n");
}
}
}
}

Answer 2

your fundamental problem is that you create a fresh student table for each command (1 and 7). So in the display command you are displaying n unitialized student records.
You also seem to have got into 'grasping at straws' mode for storing the student records, you have pointers, mallocs, dynamically sized stack arrays, 2 dimensional malloced arrays....
option 1 should malloc an array of students of the correct size. The array pointer should be declared before any of the loop code , so that yiou use the same array all the time
student *info = NULL;
int students=0;
...
while (x!=8){
.....
if(x==1){
....
info = malloc(std*sizeof(student));
}
you now have a correctly sized array . to add a student
scanf("%s", info[students].name);
etc
then `students++` to keep count of the number of active students