Implementation of Link List with basic operations

/*
Implementation of Link List with basic operations such as insert, delete, search and display.
Every node in the Link list contains data about a Railway passenger and search is based on PNR value.
*/

#include<stdio.h>
#include<stdlib.h>

/*Defining Macros*/
#define UNSUCCESSFUL 1
#define SUCCESSFUL 0

/*Defining the Node structure of the link list*/
typedef struct p_details{
    int pnr_no;
    char p_name[15];
    int p_age;
    struct p_details* next;
} p_details;

/*Function to Check, Whether an operation is sucessfull or Not*/
void Error_Check(int code)
{
    if(code == UNSUCCESSFUL)
    {
        printf("The operation was unsuccessful!\n");
    }
    else
        printf("The operation was successful!\n");
}

/*Function to display the details of a specific node in the link list */
void Display(p_details* pNode)
{
    printf("\tPassenger Information: \n \tPNR no: %d\n \t Passenger Name: %s\n \t Passenger Age: %d\n\n",pNode->pnr_no, pNode->p_name,pNode->p_age);
}

/*Function to Enter details in a Newly created Node*/
void Enter_Node_Details(p_details* pNode)
{
    char c;
    printf("\n");
    printf("Enter PNR No:\n");
    scanf("%d",&pNode->pnr_no);
    printf("Enter Passenger Name:\n");
    scanf("%s",pNode->p_name);
    printf("Enter Passenger Age:\n");
    scanf("%d",&pNode->p_age);
    pNode->next = NULL;
    printf("\n");
}

/*Function to display the details of all nodes in the link list */
void Display_All(p_details* pStart)
{
    p_details* tmp = pStart;
    if(tmp == NULL)
        {
            printf("List is empty!\n");return;
        }
    while(1)
    {
        if(tmp == NULL) break;
        Display(tmp);
        tmp = tmp->next;
    }
}

/*Function to Insert a Node at the beginning of the link list */
int Insert_At_Begining(p_details** pStart)
{
    p_details* tmp = NULL;

    tmp = (p_details*)malloc(sizeof(p_details));
    Enter_Node_Details(tmp);

    if(pStart == NULL)
    {
        *pStart = tmp;
        return SUCCESSFUL;
    }

    else
    {
        tmp->next = *pStart;
        *pStart = tmp;
        return SUCCESSFUL;
    }
    return SUCCESSFUL;
}

/*Function to Insert a Node at the end of the link list */
int Insert_At_End(p_details** pStart)
{
    p_details* tmp = NULL, *tmp2 = *pStart;

    tmp = (p_details*)malloc(sizeof(p_details));
    if(tmp == NULL)
    {
        return UNSUCCESSFUL;
    }
    Enter_Node_Details(tmp);

    if(*pStart == NULL)
    {
        *pStart = tmp; return SUCCESSFUL;
    }

    while(1)
    {
        if(tmp2->next == NULL) break;
        tmp2 = tmp2->next;
    }

    tmp2->next = tmp;
    return SUCCESSFUL;
}

/*Function to Delete a Node from the beginning of the link list */
int Delete_At_Begining(p_details** pStart)
{
    p_details* tmp = *(pStart);
    if(tmp == NULL)
    {
        printf("The list is empty!\n");
        return UNSUCCESSFUL;
    }
    *(pStart) = (*pStart)->next;
    Display(tmp);
    free(tmp);
    return SUCCESSFUL;
}

/*Function to Delete a Node from the end of the link list */
int Delete_At_End(p_details** pStart)
{
    p_details* last = *pStart;
    p_details* last2 = NULL;

    if(*pStart == NULL)
    {
        printf("List is empty!\n");
        return UNSUCCESSFUL;
    }
    if(last->next == NULL)
    {
        Display(last);
        free(last);
        *pStart = NULL;
        return SUCCESSFUL;
    }

    while(1)
    {
        if(last->next == NULL) break;
        last2 = last;
        last = last->next;
    }

    last2->next = NULL;
    Display(last);
    free(last);
    return SUCCESSFUL;
}

/*Function to Search a Node with a given key value */
int Search(p_details* pStart,int what)
{
    p_details* tmp = pStart;
    p_details* node = NULL;

    if(pStart == NULL) return UNSUCCESSFUL;

    while(1)
    {
        if(tmp == NULL) break;

        if(tmp->pnr_no == what)
        {
            node = tmp;
            break;
        }
        tmp = tmp->next;
    }

    if(node != NULL)
    {
        Display(node);
        return SUCCESSFUL;
    }
    return UNSUCCESSFUL;
}


/*Starting of the Main Function*/
int main()
{
  p_details* start = NULL;
  int c, err;
  int what;


/*Loop to receive instructions from the user*/
  while(1)
  {
    printf("Please enter a choice:\n**************************\n");
    printf("1) Insert node at beginning.\n2) Insert node at end.\n3) Delete node from beginning \n4) Delete node from end\n5) Perform search\n6) Display whole list\n7)exit\n");
   
    scanf("%d",&c);

    switch(c)
    {
    case 1:
        err = Insert_At_Begining(&start);
        Error_Check(err);
        break;
    case 2:
        err = Insert_At_End(&start);
        Error_Check(err);
        break;
    case 3:
        err = Delete_At_Begining(&start);
        Error_Check(err);
        break;
    case 4:
        err = Delete_At_End(&start);
        Error_Check(err);
        break;
    case 5:
        {
        printf("Enter the PNR No to search:\n");
        scanf("%d",&what);
        err = Search(start,what);
        Error_Check(err);
        }
        break;
    case 6:
        Display_All(start);
        break;
    case 7:   
        return 0;
        break;
    }
  }
  return 0;
}

/*End of the Program*/