Неразрешенный внешний символ - C (СИ)

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
 
struct listNode
{
    char data;
    struct listNode *nextPtr;
};
 
typedef struct listNode LISTNODE;
typedef LISTNODE *LISTNODEPTR;
 
void insert(LISTNODEPTR *sPtr, char value);
char delete(LISTNODEPTR *sPtr, char value);
int isEmpty(LISTNODEPTR *sPtr);
void printList(LISTNODEPTR currentPtr);
void instructions(void);
main()
{
    LISTNODEPTR startPtr = NULL;
    int choice;
    char item;
 
    instructions();
    pritnf("? ");
    scanf("%d", &choice);
 
    while (choice != 3) {
        switch (choice) 
        {
            case 1:
                printf("Enter a character: ");
                scanf("\n%c", &item);
                insert(&startPtr, item);
                printList(startPtr);
                break;
            case 2:
                if (!isEmpty(startPtr)) {
                    printf("Enter character to be deleted: ");
                    scanf("\n%c", &item);
 
                    if (delete(&startPtr, item)) {
                        printf("%c deleted", item);
                        printList(startPtr);
                    }
                    else{
                        printf("%c not found.\n\n", item);
                    }
                }
                else {
                    printf("List is empty\n\n");
                }
                break;
            default:
                printf("Invalid choice.\n\n");
                instructions();
                break;
        }
        printf("? ");
        scanf("%d", &choice);
    }
 
    printf("End of run.\n");
    return 0;
}
 
// Print the menu
void instructions(void)
{
    printf("Enter your choice: \n"
        "1 - to insert an element into the list.\n"
        "2 - to delite an element from the list.\n"
        "3 - to end.\n");
}
 
//Вставка нового значения в упорядоченный список
void insert(LISTNODEPTR *sPtr, char value)
{
    LISTNODEPTR newPtr, previousPtr, currentPtr;
 
    newPtr = malloc(sizeof(LISTNODE));
 
    if (newPtr != NULL) {
        newPtr->data = value;
        newPtr->nextPtr = NULL;
 
        previousPtr = NULL;
        currentPtr = *sPtr;
 
        while (currentPtr != NULL && value > currentPtr->data) {
            previousPtr = currentPtr;
            currentPtr = currentPtr->nextPtr;
        }
 
        if (previousPtr == NULL) {
            newPtr->nextPtr = *sPtr;
            *sPtr = newPtr;
        }
        else {
            previousPtr->nextPtr;
            newPtr->nextPtr = currentPtr;
        }
    }
    else {
        printf("%c not inserted. No memory available.\n", value);
    }
}
//Удаление элемента из списка
char delete(LISTNODEPTR *sPtr, char value)
{
    LISTNODEPTR previousPtr, currentPtr, tempPtr;
 
    if (value == (*sPtr)->data) {
        tempPtr = *sPtr;
        *sPtr = (*sPtr)->nextPtr;
        free(tempPtr);
        return value;
    }
    else {
        previousPtr = *sPtr;
        currentPtr = (*sPtr)->nextPtr;
 
        while (currentPtr != NULL && currentPtr->data != value) {
            previousPtr = currentPtr;
            currentPtr = currentPtr->nextPtr;
        }
        if (currentPtr != NULL) {
            tempPtr = currentPtr;
            previousPtr->nextPtr = currentPtr->nextPtr;
            free(tempPtr);
            return value;
        }
    }
    return '\0';
}
 
//if the list is empty , the function will return 1 , else - 0
int isEmpty(LISTNODEPTR *sPtr)
{
    return sPtr = NULL;
}
 
//print the list
void printList(LISTNODEPTR currentPtr)
{
    if (currentPtr == NULL){
        printf("List is empty.\n\n");
    }
    else {
        printf("The list is: \n");
 
        while (currentPtr != NULL) {
            printf("%c->", currentPtr->data);
            currentPtr = currentPtr->nextPtr;
        }
        printf("NULL\n\n");
    }
}