Double linked list

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <string.h>
#define N 100

struct dlinklist
{
    struct dlinklist *prev;  /** Stores address of previous node **/
    int roll_no;             /** stores roll number **/
    char name[N];            /** stores Name **/
    float marks;             /** stores Marks **/
    struct dlinklist *next;  /** stores address of next node **/
};

/** Redefining dlinklist as node **/
typedef struct dlinklist node;

void init(node*);     /** Input function **/
void ins_aft(node*);  /** Function inserting before **/
node* ins_bef(node*); /** Function inserting after **/
node* del(node*);     /** Function deleting a node **/
void search(node*);   /** Function for searching node **/
void disp(node*);     /** Function for displaying node **/
void rollsrch(node*); /** Function for searching node by roll number **/
void namesrch(node*); /** Function for searching node by name **/
void marksrch(node*); /** Function for searching node by marks **/

void main()
{
    node *head;
    char ch;                         /* Choice inputing varible */
    int opt;                         /* Option inputing variable*/
    static int flag=0;               /* Unchanged after iniialization */
    clrscr();
    head=(node*)malloc(sizeof(node));
    head->next=NULL;
    head->prev=NULL;
    do
    {
again:
    printf("\nEnter your option\n");
    printf("\n1. Initialize the node\n");
    printf("\n2. Insert before a specified node\n");
    printf("\n3. Insert after a specified node\n");
    printf("\n4. Delete a particular node\n");
    printf("\n5. Search the nodes\n");
    printf("\n6. Display all the nodes\n");
    scanf("%d",&opt);
    if(flag==0 && opt!=1)
    {
        printf("\nNo. You must first initialize at least one node\n");
        goto again;
    }
    if(flag==1 && opt==1)
    {
        printf("\nInitialisation can occur only once.\n");
        printf("\nNow you can insert a node\n");
        goto again;
    }
    if(opt==4 && head->next==NULL)
    {
        printf("\nYou cannot delete the one and only the single node\n");
        goto again;
    }
    if(flag==0 && opt==1)
        flag=1;
    switch(opt)
    {
    case 1:
        init(head);
        break;
    case 2:
        head=ins_bef(head);
        break;
    case 3:
        ins_aft(head);
        break;
    case 4:
        head=del(head);
        break;
    case 5:
        search(head);
        break;
    case 6:
        disp(head);
        break;
    }
    printf("\nDo you wish to continue[y/n]\n");
    ch=getche();
    }while(ch=='Y' || ch=='y');
    printf("\nDone by \"SHABBIR\"\n");
    printf("\nPress any key to exit\n");
    getch();
}

void init(node *current)
{
    current->prev=NULL;
    printf("\nEnter Roll number\n");
    scanf("%d",&current->roll_no);
    printf("\nEnter the name\n");
    fflush(stdin);
    gets(current->name);
    printf("\nEnter the marks\n");
    scanf("%f",&current->marks);
    current->next=NULL;
}

void ins_aft(node *current)
{
    int rno;             /* Roll number for inserting a node*/
    int flag=0;
    node *newnode;
    newnode=(node*)malloc(sizeof(node));
    printf("\nEnter the roll number after which you want to insert a node\n");
    scanf("%d",&rno);
    init(newnode);
    while(current->next!=NULL)
    {
        /***  Insertion checking for all nodes except last  ***/
        if(current->roll_no==rno)
        {
            newnode->next=current->next;
            current->next->prev=newnode;
            current->next=newnode;
            newnode->prev=current;
            flag=1;
        }
        current=current->next;
    }
    if(flag==0 && current->next==NULL && current->roll_no==rno)
    {
        /***  Insertion checking for last nodes  ***/
        newnode->next=current->next;
        current->next=newnode;
        flag=1;
    }
    else if(flag==0 && current->next==NULL)
        printf("\nNo match found\n");
}

node* ins_bef(node *current)
{
    int rno;            /* Roll number for inserting a node*/
    node *newnode,*temp;
    newnode=(node*)malloc(sizeof(node));
    printf("\nEnter the roll number before which you want to insert a node\n");
    scanf("%d",&rno);
    init(newnode);
    if(current->roll_no==rno)
    {
        /*** Insertion checking for first node ***/
        newnode->next=current;
        current->prev=newnode;
        current=newnode;
        return(current);
    }
    temp=current;
    while(temp->next!=NULL)
    {                                       
        /*** Insertion checking for all node except first ***/
        if(temp->next->roll_no==rno)
        {
            newnode->next=temp->next;
            temp->next->prev=newnode;
            temp->next=newnode;
            newnode->prev=temp;
            return(current);
        }
        temp=temp->next;
    }
    /*
    If the function does not return from any return statement.
    There is no match to insert before the input  roll number.
    */
    printf("\nMatch not found\n");
    return(current);
}

node* del(node *current)
{
    int rno;               /* Roll number for deleting a node*/
    node *newnode,*temp;
    printf("\nEnter the roll number whose node you want to delete\n");
    scanf("%d",&rno);
    newnode=current;
    if(current->roll_no==rno)
    {
        /***  Checking condition for deletion of first node  ***/
        newnode=current; /*  Unnecessary step  */
        current=current->next;
        current->prev=NULL;
        free(newnode);
        return(current);
    }
    else
    {
        while(newnode->next->next!=NULL)
        {
            /***  Checking condition for deletion of   ***/
            /*** all nodes except first and last node  ***/
            if(current->next->roll_no==rno)
            {
                newnode=current;
                temp=current->next;
                newnode->next=newnode->next->next;
                newnode->next->prev=current;
                free(temp);
                return(current);
            }
            newnode=newnode->next;
        }
        if(newnode->next->next==NULL && newnode->next->roll_no==rno)
        {
            /***  Checking condition for deletion of last node  ***/
            temp=newnode->next;
            free(temp);
            newnode->next=NULL;
            return(current);
        }
    }
    printf("\nMatch not found\n");
    return(current);
}

void search(node *current)
{
    int ch;                  /* Choice inputing variable */
    printf("\nEnter the criteria for search\n");
    printf("\n1. Roll number\n");
    printf("\n2. Name\n");
    printf("\n3. Marks\n");
    scanf("%d",&ch);
    switch(ch)
    {
    case 1:
        rollsrch(current);
        break;
    case 2:
        namesrch(current);
        break;
    case 3:
        marksrch(current);
        break;
    default:
        rollsrch(current);
    }
}

void rollsrch(node *current)
{
    int rno;
    printf("\nEnter the roll number to search\n");
    scanf("%d",&rno);
    while(current->next!=NULL)
    {
        if(current->roll_no==rno)
            printf("\n%d\t%s\t%f\n",current->roll_no,current->name,current->marks);
        current=current->next;
    }
    if(current->next==NULL && current->roll_no==rno)
        printf("\n%d\t%s\t%f\n",current->roll_no,current->name,current->marks);
}

void namesrch(node *current)
{
    char arr[20];
    printf("\nEnter the name to search\n");
    fflush(stdin);
    gets(arr);
    while(current->next!=NULL)
    {
        if(strcmp(current->name,arr)==NULL)
            printf("\n%d\t%s\t%f\n",current->roll_no,current->name,current->marks);
        current=current->next;
    }
    if(current->next==NULL && strcmp(current->name,arr)==NULL)
        printf("\n%d\t%s\t%f\n",current->roll_no,current->name,current->marks);
}

void marksrch(node *current)
{
    float marks;
    printf("\nEnter the marks to search\n");
    scanf("%f",&marks);
    while(current->next!=NULL)
    {
        if(current->marks==marks)
            printf("\n%d\t%s\t%f\n",current->roll_no,current->name,current->marks);
        current=current->next;
    }
    if(current->next==NULL && current->marks==marks)
        printf("\n%d\t%s\t%f\n",current->roll_no,current->name,current->marks);
}

void disp(node *current)
{
    while(current!=NULL)
    {
        printf("\n%d\t%s\t%f",current->roll_no,current->name,current->marks);
        current=current->next;
    }
}