Search for a node in a linked list

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

struct digit {
    int num;
    struct digit *next;
};

struct digit * createDigit(int);
struct digit * append(struct digit * end, struct digit * newDigptr);
void printNumber(struct digit *);
void freeNumber(struct digit *start);
struct digit * readNumber();
struct digit * searchNumber(struct digit * start, int number);

int main(void) {
    //! stack = showMemory(start=65520)
    struct digit *start, *ptr;
    int searchNum = 5;
    printf("Please enter a number: ");
    start = readNumber();
    printNumber(start);
    ptr = searchNumber(start, searchNum);
    if (ptr!=NULL) {
        printf("Found digit %d at location %p.\n", searchNum, ptr);
    } else {
        printf("Digit %d not found.\n", searchNum);
    }
    freeNumber(start);
    return 0;
}

struct digit *createDigit(int dig) {
    struct digit *ptr;
    ptr = (struct digit *) malloc(sizeof(struct digit));
    ptr->num = dig;
    ptr->next = NULL;
    return ptr;
}

struct digit * append(struct digit * end, struct digit * newDigptr) {
    end->next = newDigptr;
    return(end->next);
}

void printNumber(struct digit *start) {
    struct digit * ptr = start;
    while (ptr!=NULL) {
        printf("%d", ptr->num);
        ptr = ptr->next;
    }
    printf("\n");
}

void freeNumber(struct digit *start) {
    struct digit * ptr = start;
    struct digit * tmp;
    while (ptr!=NULL) {
        tmp = ptr->next;
        free(ptr);
        ptr = tmp;
    }
}

struct digit * readNumber() {
    //! heap=showMemory(start=309, cursors=[start, end, newptr])
    char c;
    int d;
    struct digit *start, *end, *newptr;
    start = NULL;
    scanf("%c", &c);
    while (c!='\n') {
        d = c - 48;
        newptr = createDigit(d);
        if (start==NULL) {
            start = newptr;
            end = start;
        } else {
            end = append(end, newptr);
        }
        scanf("%c", &c);
    }
    return start;
}

struct digit * searchNumber(struct digit * start, int number) {
//! heap=showMemory(start=348, cursors=[ptr,start])
    struct digit * ptr = start;
    while ((ptr!=NULL) && (ptr->num!=number)) {
        ptr = ptr->next;
    }
    return(ptr);
}