Realization of readable and writable files in library management system with C language bidirectional linked list

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

int nCount = 0;

// Book structure 
typedef struct Node {
	struct Node * Blink;
	struct Node * Flink;
	char BookName[50];
	float BookPrice;
	int BookNumber;
};

struct Node * ndHeaderNode = NULL;

// Add book functions 
struct Node * AppendNode(struct Node * CurrentNode, char * BookName, int BookNumber, float BookPrice)
{
	struct Node * pNewNode = NULL;
	struct Node * pTempNode = NULL;
	struct Node * pHeadNode = CurrentNode;
	pNewNode = (struct Node *)malloc(sizeof(struct Node));
	if (pNewNode == NULL)
	{
		printf("memory malloc failed!\n");
		return pNewNode;
	}
	if (CurrentNode == NULL)
	{
		CurrentNode = pNewNode;
		CurrentNode->Blink = NULL;
		CurrentNode->Flink = NULL;
	}
	else
	{
		while (pHeadNode->Flink != NULL)
		{
			pTempNode = pHeadNode;
			pHeadNode = pHeadNode->Flink;
		}
		pHeadNode->Flink = pNewNode;
		pHeadNode->Blink = pTempNode;
	}
	strcpy(pNewNode->BookName, BookName);
	pNewNode->BookPrice = BookPrice;
	pNewNode->BookNumber = BookNumber;
	pNewNode->Flink = NULL;
	nCount++;
	return CurrentNode;
}
// Functions for querying books 
void QueryNode(struct Node * HeaderNode, char * BookName)
{
	if (HeaderNode == NULL)
	{
		printf("ERROR:HeaderNode == NULL\n");
		return;
	}
	if (strcmp(HeaderNode->BookName, BookName) == 0)
	{
		printf(" Title ：%s\n", HeaderNode->BookName);
		printf(" pricing ：%f\n", HeaderNode->BookPrice);
		printf(" Book number ：%d\n", HeaderNode->BookNumber);
		return;
	}
	while (HeaderNode->Flink != NULL)
	{
		HeaderNode = HeaderNode->Flink;
		if (strcmp(HeaderNode->BookName, BookName) == 0)
		{
			printf(" Title ：%s\n", HeaderNode->BookName);
			printf(" pricing ：%f\n", HeaderNode->BookPrice);
			printf(" Book number ：%d\n", HeaderNode->BookNumber);
			return;
		}
	}
	printf("Can Not Found!\n");
}
// Modify book information 
void ModifyNode(struct Node * HeaderNode, char * BookName, float BookPrice)
{
	if (HeaderNode == NULL)
	{
		printf("ERROR:HeaderNode == NULL\n");
		return;
	}
	if (strcmp(HeaderNode->BookName, BookName) == 0)
	{
		HeaderNode->BookPrice = BookPrice;
		printf("ModifyNode Success!\n");
		return;
	}
	while (HeaderNode->Flink != NULL)
	{
		HeaderNode = HeaderNode->Flink;
		if (strcmp(HeaderNode->BookName, BookName) == 0)
		{
			HeaderNode->BookPrice = BookPrice;
			printf("ModifyNode Success!\n");
			return;
		}
	}

	printf("ModifyNode Failed!\n");
	return;
}
// Delete book functions 
void DeleteNode(struct Node * HeaderNode, char * BookName)
{
	struct Node * pNode = NULL;
	pNode = HeaderNode;
	for (size_t i = 0; i < nCount; i++)
	{
		if (strcmp(pNode->BookName, BookName) == 0)
		{
			if (pNode == HeaderNode)
			{
				pNode = HeaderNode->Flink;
				free(HeaderNode);
				ndHeaderNode = pNode;
				HeaderNode = ndHeaderNode;
				nCount--;
				return;
			}
			if (pNode->Flink == NULL)
			{
				pNode->Blink->Flink = NULL;
				free(pNode);
				nCount--;
				printf("Delete Success!\n");
				return;
			}

			pNode->Blink->Flink = pNode->Flink;
			pNode->Flink->Blink = pNode->Blink;
			free(pNode);
			nCount--;
			printf("Delete Success!\n");
			return;
		}
	}
}
// Write the contents of the book to a file 
void WriteFile(struct Node * HeaderNode, char * szFilePath)
{
	struct Node *p = HeaderNode;
	FILE * w = fopen(szFilePath, "wb");
	if (w == NULL)
	{
		printf("open file failed!\n");
		system("pause");
		fclose(w);
		exit(0);//0 The normal exit  1 Abnormal exit 
	}
	while (p)
	{
		// Output linked list node data to the screen  
		printf("%s ", p->BookName);
		printf("%f ", p->BookPrice);
		printf("%d ", p->BookNumber);
		printf("\n");
		// Output linked list node data to file output.txt 
		fprintf(w, "%s ", p->BookName);
		fprintf(w, "%f ", p->BookPrice);
		fprintf(w, "%d", p->BookNumber);
		fprintf(w, "\n");
		p = p->Flink;
	}
	fprintf(w, "\n");
	fclose(w);
	return;

}
// Read file contents 
struct Node * ReadFile(char * szFilePath)
{
	struct Node * head = (struct Node *)malloc(sizeof(struct Node));
	head->Blink = NULL;
	head->Flink = NULL;
	char name[50];
	memset(name, 0, 50);
	float price;
	int number;
	struct Node * p;
	struct Node * q;
	p = q = head;
	FILE * r = fopen(szFilePath, "rb");
	if (r == NULL)
	{
		printf("open file failed!\n");
		system("pause");
		fclose(r);
		exit(0);//0 The normal exit  1 Abnormal exit 
	}
	while (fscanf(r, "%s", name) != EOF)
	{
		q = (struct Node *)malloc(sizeof(struct Node));
		fscanf(r, "%f", &price);
		fscanf(r, "%d", &number);
		strcpy(q->BookName, name);
		q->BookPrice = price;
		q->BookNumber = number;
		q->Blink = p;
		p->Flink = q;
		p = q;
	}
	p->Flink = NULL;
	return head->Flink;
}
// Show all book information 
void show(struct Node * HeaderNode)
{
	printf(" Title ：%s\n", HeaderNode->BookName);
	printf(" pricing ：%f\n", HeaderNode->BookPrice);
	printf(" Book number ：%d\n", HeaderNode->BookNumber);
	while (HeaderNode->Flink != NULL)
	{
		HeaderNode = HeaderNode->Flink;
		printf(" Title ：%s\n", HeaderNode->BookName);
		printf(" pricing ：%f\n", HeaderNode->BookPrice);
		printf(" Book number ：%d\n", HeaderNode->BookNumber);
	}
}
void Start()
{
	while (1)
	{
		int nFlag = 0;
		int ReadFlag = 0;
		char szBookName[50];
		float fBookPrice = 0;
		float fNewBookPrice = 0;
		int nBookNumber = 0;
		printf(" Please enter the function you want to use :\n");
		printf("1. Add book information \n");
		printf("2. Search for book information \n");
		printf("3. Modify book information \n");
		printf("4. Delete book information \n");
		printf("5. Store book information in a file \n");
		printf("6. Read book information from file \n");
		printf("7. Show all book information \n");
		printf("8. sign out \n");
		scanf("%d", &ReadFlag);
		switch (ReadFlag)
		{
		case 1:
			//memset(szBookName, 0 ,50);
			printf(" Please enter the title of the book ：");
			scanf("%s", szBookName);
			printf(" Please enter the pricing  ：");
			scanf("%f", &fBookPrice);
			printf(" Please enter the book number ：");
			scanf("%d", &nBookNumber);
			// New function 
			ndHeaderNode = AppendNode(ndHeaderNode, szBookName, nBookNumber, fBookPrice);
			break;
		case 2:
			printf(" Please enter the title of the book ：");
			scanf("%s", szBookName);
			// Query function 
			QueryNode(ndHeaderNode, szBookName);
			break;
		case 3:
			printf(" Please enter the title of the book ：");
			scanf("%s", szBookName);
			printf(" Please enter the new pricing ：");
			scanf("%f", &fNewBookPrice);
			//code  Modified function 
			ModifyNode(ndHeaderNode, szBookName, fNewBookPrice);
			break;
		case 4:
			printf(" Please enter the title of the book ：");
			scanf("%s", szBookName);
			// Delete function 
			DeleteNode(ndHeaderNode, szBookName);
			break;
		case 5:
			//C:\Users\rkvir\Documents\Visual Studio 2015\Projects
			WriteFile(ndHeaderNode, "information.txt");
			break;
		case 6:
			ndHeaderNode = ReadFile("information.txt");
			break;
		case 7:
			show(ndHeaderNode);
			break;
		case 8:
			nFlag = 1;
			break;
		}
		if (nFlag)
		{
			break;
		}
	}
}
int main()
{
	Start();
	return 0;
}