Thanks, it was just i had to free pointer so i free it without declaring the pointer as NULL especially that this variable is used by the dll as global variable but now everything is ok thanks :) emma :)

imanos wrote: i don't want to create new file and write the old one again Why not? Just create a temporary file with the new list of wanted words, rename the original first file, and rename the temporary file to the original name of the first file...

FILE* vl_fp=fopen("Data.txt","w") fprintf(vl_fp,"%2X",stemp); fclose(vl_fp)

u know sscanf worked for me but sure i'll try all the solutions to have them all Thanks for ur valuable time ur all great thanks emma :)