Compilare: user.cpp: In function ‘int main()’: user.cpp:12:19: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] a[strlen(a)-1]=NULL; ^ user.cpp:17:17: warning: NULL used in arithmetic [-Wpointer-arith] for(p=a;*p!=NULL;p++) ^ user.cpp:28:22: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] *p=NULL; ^ user.cpp:40:24: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] *p=NULL; ^ user.cpp:11:20: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(a,1600,f); ^