c - Will memory be allocated for a typedef structure pointer? -

i have following program, have structure. going assign values , write file. confusion here is, have declared pointer structure , has not allocated memory. how variable assignment works? able retrieve values correctly file "/home/info"

#include <stdio.h> #define filee "/home/info"  typedef struct my_info {    int i;    int j;    int k;    int l; }_my_info;  void main() {     _my_info *my_info;     int fd;     file *fp;     my_info->i=100;     my_info->j=300;     my_info->k=200;     my_info->l=400;     fp = fopen(filee,"w");     if (fp == null)         printf("error in opening file\n");     fd=fwrite(my_info, sizeof(_my_info), 1, fp);     if (fd<0)         printf("error while writing\n");     fclose(fp); } 

when declare my_info

_my_info *my_info; 

it have undefined value. in case, value of my_info within range of valid memory addresses ram. write it, , read take place.

however, don't know other memory changing due this. may cause memory corruption, in larger programs.