Storing and Display info using Structure

#include<conio.h>

#include<alloc.h>

#include<stdio.h>

struct data{

            char name[45];

            int roll,m1,m2,m3,t;

            float avg;

};

struct stu{

            struct data d;

            struct stu *next;

}*head=NULL,*temp,*node;

void in(char *,int,int,int,int), dis(void);

void main()

{

            char *n;

            int r,x,y,z;

            printf("\nMain Menu\n1.Insert details\n2.Display\n3.Exit\nEnter choice:");

            scanf("%d",&r);

            switch(r)

            {

                        case 1:

                                    getc(stdin);

                                    printf("Enter name of the student:");

                                    gets(n);

                                    printf("Enter roll number:");

                                    scanf("%d",&r);

                                    printf("Enter marks of three subjects:");

                                    scanf("%d%d%d",&x,&y,&z);

                                    in(n,r,x,y,z);

                                    break;

                        case 2:

                                    clrscr();

                                    if(head==NULL)

                                                printf("EMPTY RECORDS!!");

                                    else

                                    {

                                                puts("\nThe records are:\n");

                                                printf("\tName\t\tRoll\tMarks\tMarks\tMarks\tTotal\tAverage\n");

                                                dis();

                                    }

                                    break;

                        case 3:

                                    clrscr();

                                    exit();

                        default:

                                    clrscr();

                                    printf("WRONG INPUT!!");

            }

            main();

}

void in(char *n,int r, int x,int y, int z)

{

            if(head==NULL)

            {

                        head=(struct stu*)malloc(sizeof(struct stu));

                        strcpy(head->d.name,n);

                        head->d.roll=r;

                        head->d.m1=x;

                        head->d.m2=y;

                        head->d.m3=z;

                        head->d.t=x+y+z;

                        head->d.avg=head->d.t/3;

                        head->next=NULL;

            }

            else

            {

                        temp=head;

                        while(temp->next!=NULL)

                                    temp=temp->next;

                        node=(struct stu*)malloc(sizeof(struct stu));

                        strcpy(node->d.name,n);

                        node->d.roll=r;

                        node->d.m1=x;

                        node->d.m2=y;

                        node->d.m3=z;

                        node->d.t=x+y+z;

                        node->d.avg=node->d.t/3;

                        temp->next=node;

            }

}

void dis(void)

{

            int max=head->d.t;

            temp=head;

            while(temp!=NULL)

            {

                        printf("%s\t%d\t%d\t%d\t%d\t%d\t%.2f\n",temp->d.name,

                        temp->d.roll,temp->d.m1,temp->d.m2,temp->d.m3,temp->d.t,temp->d.avg);

                        if(temp->d.t>max)

                                    max=temp->d.t;

                                    temp=temp->next;

            }

            printf("The student to obtain highest marks is:\nName: %s\nRoll: %d\nMarks: %d, %d and %d\nTotal: %d\nAverage: %.2f",temp->d.name,temp->d.roll,temp->d.m1,temp->d.m2,temp->d.m3,temp->d.t,temp->d.avg);

}