C Program of initializing a singly linked list.

Initializing a singly linked list in C programming language.

What is singly linked list.?

#include<stdio.h>
#include<conio.h>
#include<process.h>
#include<stdlib.h>
struct node
{
    int data;
    struct node *next;
}*start=NULL,*q,*t;
int main()
{
    int ch;

    void insert_beg();
    void insert_end();
    int insert_pos();
    void display();
    void delete_beg();
    void delete_end();
    int delete_pos();
    while(1)
    {
	printf("\n\n---- Singly Linked List(SLL) Menu ----");
	printf("\n1.Insert\n2.Display\n3.Delete\n4.Exit\n\n");
	printf("Enter your choice(1-4):");
	scanf("%d",&ch);
	switch(ch)
	{
	    case 1:
		    printf("\n---- Insert Menu ----");
		    printf("\n1.Insert at beginning\n2.Insert at end\n3.Insert at specified position\n4.Exit");
		    printf("\n\nEnter your choice(1-4):");
		    scanf("%d",&ch);
		    switch(ch)
		    {
			case 1: insert_beg();
				break;
			case 2: insert_end();
				break;
			case 3: insert_pos();
				break;
			case 4: exit(0);
			default: printf("Wrong Choice!!");
		    }
		    break;

	    case 2: display();
		    break;
	    case 3: printf("\n---- Delete Menu ----");
		    printf("\n1.Delete from beginning\n2.Delete from end\n3.Delete from specified position\n4.Exit");
		    printf("\n\nEnter your choice(1-4):");
		    scanf("%d",&ch);
		    switch(ch)
		    {
			case 1: delete_beg();
				break;
			case 2: delete_end();
				break;
			case 3: delete_pos();
				break;
			case 4: exit(0);
			default: printf("Wrong Choice!!");
		    }
		    break;
	    case 4: exit(0);
		    default: printf("Wrong Choice!!");
	} 
 }
    return 0;
}
void insert_beg()
{
    int num;
    t=(struct node*)malloc(sizeof(struct node));
    printf("Enter data:");
    scanf("%d",&num);
    t->data=num;
    if(start==NULL)        //If list is empty
    {
	t->next=NULL;
	start=t;
    }
    else
    {
	t->next=start;
	start=t;
    } 
 }
void insert_end()
{
    int num;
    t=(struct node*)malloc(sizeof(struct node));
    printf("Enter data:");
    scanf("%d",&num);
    t->data=num;
    t->next=NULL;
    if(start==NULL)        //If list is empty
    {
	start=t;
    }
    else
    {
	q=start;
	while(q->next!=NULL)
	q=q->next;
	q->next=t;
    } 
 }
int insert_pos()
{
    int pos,i,num;
    if(start==NULL)
    {
	printf("List is empty!!");
	return 0;
    }
    t=(struct node*)malloc(sizeof(struct node));
    printf("Enter data:");
    scanf("%d",&num);
    printf("Enter position to insert:");
    scanf("%d",&pos);
    t->data=num;
    q=start;
    for(i=1;i<pos-1;i++)
    {
	if(q->next==NULL)
	{
	    printf("There are less elements!!");
	    return 0;
	}
	q=q->next;
    }
    t->next=q->next;
    q->next=t;
    return 0;
}
void display()
{
    if(start==NULL)
    {
	printf("List is empty!!");
    }
    else
    {
	q=start;
	printf("The linked list is:\n");
	while(q!=NULL)
	{
             printf("%d->",q->data);
	    q=q->next;
	}
    printf("NULL");
} 
      }
void delete_beg()
{
    if(start==NULL)
    {
	printf("The list is empty!!");
    }
    else
    {
        q=start;
        start=start->next;
        printf("Deleted element is %d",q->data);
        free(q);
    } 
 }
void delete_end()
{
    if(start==NULL)
    {
        printf("The list is empty!!");
    }
    else
    {
        q=start;
        while(q->next->next!=NULL)
        q=q->next;
        t=q->next;
        q->next=NULL;
        printf("Deleted element is %d",t->data);
        free(t);
    }  
 ]
int delete_pos()
{
    int pos,i;
    if(start==NULL)
    {
        printf("List is empty!!");
        return 0;
    }
    printf("Enter position to delete:");
    scanf("%d",&pos);
    q=start;
    for(i=1;i<pos-1;i++)
    {
        if(q->next==NULL)
        {
            printf("There are less elements!!");
            return 0;   }
        q=q->next;
    }
    t=q->next;
    q->next=t->next;
    printf("Deleted element is %d",t->data);
    free(t);
 
    return 0;
}