program.exe已停止工作（c）

Question

In case my question is stupid or has already been answered, you'll have to excuse me, since it's the 1st time I am using the forum + when it comes to programming I am still a newbie. I will learn in time.

Anyway, I wrote some lines of code which do not seem to work. When I am compiling and running the program, a small window pops which says that "myprogram.exe has stopped working" and that windows is checking a solution to the problem. If it gives you any clue, I am using codeblocks.

Here is the program:

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

int main(void)
{
    char *ptr,*p;
    p=ptr;
    ptr="Lineage";
    while (*ptr!='\0')
        ptr++;
    ptr--;
    while (ptr>=p)
        {
        putchar(*ptr);
        ptr--;
        }
    return 0;
}

Answer 1

while (ptr>=p)

p pointer is uninitalized. Using uninitialized values leads to UB.

You are assigning ptr to p . At that point ptr itself is not pointing to any valid memory location.