Unresolved external symbol in c for user-define function - c

Question

im very new to programming and for my course we learning c language so have mercy on my badly written code and the compiler just wont run the program because of the error so its hard for me to identify whats wrong.Back to main question im getting unresolved external symbol...referenced in function_main and i dont really know where im messed up
#include<stdio.h>
char DisplayMenu(void);
void ViewBooks();
void SearchBookPrice();
void UpdateBookPrice();
int main()
{
char userchoice;
int bookID[5] = { 200,230,500,540,700 };
char bookTitle[5][50] = { {"Using Information Technology 12th Edition" }, { "Beyond HTML" },{"Build Your Own PC"},{"Instant Java Servlets"},{"DIgital Image: A Practical Guide"} };
float bookPrice[5] = { 100.30,50.40,47,83.30,22.90 };
do
{
userchoice = DisplayMenu();
if (userchoice == 'V')
ViewBooks();
else if (userchoice == 'S')
SearchBookPrice();
else if (userchoice == 'U')
UpdateBookPrice();
} while (userchoice != 'E');
printf("Thank you for using our system. Have a nice day!\n");
return 0;
}
char DisplayMenu(void)
{
char choice;
printf("*************************************************************************\n");
printf("V:View Books S:Search Book Price U:Update Book Price E:Exit");
printf("*************************************************************************\n");
do
{
printf("Enter your choice: ");
scanf(" %c", &choice);
if (choice != 'V' && choice != 'S' && choice != 'U' && choice != 'E')
printf("Invalid Choice\n");
} while (choice != 'V' && choice != 'S' && choice != 'U' && choice != 'E');
return choice;
}
void ViewBooks(int bookID[],float bookPrice[])
{
printf("%d Using Information Technology 12th Edition $%f\n", bookID[0], bookPrice[0]);
printf("%d Beyond HTML $%f\n", bookID[1], bookPrice[1]);
printf("%d Build Your Own PC $%f\n", bookID[2], bookPrice[2]);
printf("%d Instant Java Servlets $%f\n", bookID[3], bookPrice[3]);
printf("%d Digital Image: A Pratical Guide $%f\n", bookID[4], bookPrice[4]);
return;
}
void SearchBookPrice(int bookID[5],char bookTitle[5][50], float bookPrice[5])
{
int idsearch, i= 0, match = -1;
printf("*************************************************************************\n");
printf("Search by book ID\n");
printf("*************************************************************************\n");
printf("Enter book ID: ");
scanf("%d", &idsearch);
while (i<5 && match==-1)
{
if (bookID[i] == idsearch)
match = i;
i++;
}
if (match == -1)
printf("Please refer to the customer service for assitance");
else
{
printf("The book id is : %d\n", &idsearch);
printf("The price of %s is %f", bookTitle[match], bookPrice[match]);
}
return;
}
void UpdateBookPrice(int bookID[5], char bookTitle[5][50], float bookPrice[5])
{
int idsearch, i = 0, match = -1;
printf("Enter book ID: ");
scanf("%d", &idsearch);
while (i < 5 && match == -1)
{
if (bookID[i] == idsearch)
match = i;
i++;
}
if (match == -1)
printf("The book ID is not found. Please make sure the book ID is correct");
else
{
printf("Current book price is %f\n", bookPrice[match]);
printf("Enter new price for (%d-%s): ", bookID[match], bookTitle[match]);
scanf("%f", &bookPrice[match]);
}
return;
}

Answer 1

Your function declaration is not matched with function body.
This is working code.
#include<stdio.h>
char DisplayMenu(void);
void ViewBooks(int bookID[],float bookPrice[]);
void SearchBookPrice(int bookID[5],char bookTitle[5][50], float bookPrice[5]);
void UpdateBookPrice(int bookID[5], char bookTitle[5][50], float bookPrice[5]);
int main()
{
char userchoice;
int bookID[5] = { 200,230,500,540,700 };
char bookTitle[5][50] = { {"Using Information Technology 12th Edition" }, { "Beyond HTML" },{"Build Your Own PC"},{"Instant Java Servlets"},{"DIgital Image: A Practical Guide"} };
float bookPrice[5] = { 100.30,50.40,47,83.30,22.90 };
do
{
userchoice = DisplayMenu();
if (userchoice == 'V')
ViewBooks(bookID, bookPrice);
else if (userchoice == 'S')
SearchBookPrice(bookID, bookTitle, bookPrice);
else if (userchoice == 'U')
UpdateBookPrice(bookID, bookTitle, bookPrice);
} while (userchoice != 'E');
printf("Thank you for using our system. Have a nice day!\n");
return 0;
}
char DisplayMenu(void)
{
char choice;
printf("*************************************************************************\n");
printf("V:View Books S:Search Book Price U:Update Book Price E:Exit");
printf("*************************************************************************\n");
do
{
printf("Enter your choice: ");
scanf(" %c", &choice);
if (choice != 'V' && choice != 'S' && choice != 'U' && choice != 'E')
printf("Invalid Choice\n");
} while (choice != 'V' && choice != 'S' && choice != 'U' && choice != 'E');
return choice;
}
void ViewBooks(int bookID[],float bookPrice[])
{
printf("%d Using Information Technology 12th Edition $%f\n", bookID[0], bookPrice[0]);
printf("%d Beyond HTML $%f\n", bookID[1], bookPrice[1]);
printf("%d Build Your Own PC $%f\n", bookID[2], bookPrice[2]);
printf("%d Instant Java Servlets $%f\n", bookID[3], bookPrice[3]);
printf("%d Digital Image: A Pratical Guide $%f\n", bookID[4], bookPrice[4]);
return;
}
void SearchBookPrice(int bookID[5],char bookTitle[5][50], float bookPrice[5])
{
int idsearch, i= 0, match = -1;
printf("*************************************************************************\n");
printf("Search by book ID\n");
printf("*************************************************************************\n");
printf("Enter book ID: ");
scanf("%d", &idsearch);
while (i<5 && match==-1)
{
if (bookID[i] == idsearch)
match = i;
i++;
}
if (match == -1)
printf("Please refer to the customer service for assitance");
else
{
printf("The book id is : %d\n", &idsearch);
printf("The price of %s is %f", bookTitle[match], bookPrice[match]);
}
return;
}
void UpdateBookPrice(int bookID[5], char bookTitle[5][50], float bookPrice[5])
{
int idsearch, i = 0, match = -1;
printf("Enter book ID: ");
scanf("%d", &idsearch);
while (i < 5 && match == -1)
{
if (bookID[i] == idsearch)
match = i;
i++;
}
if (match == -1)
printf("The book ID is not found. Please make sure the book ID is correct");
else
{
printf("Current book price is %f\n", bookPrice[match]);
printf("Enter new price for (%d-%s): ", bookID[match], bookTitle[match]);
scanf("%f", &bookPrice[match]);
}
return;
}