> what's your meaning of raw memory? > > it not image data, but a struct data, i mean no offense by this, but those two statements reveal that your understanding of working with memory in C could use some improvement before trying to work with "raw memory images" of data, i.e. blobs. In doing so, you will learn why storing data that way is only useful in very specialized cases. Unfortunately, it's been almost 30 years since i first learned C, so cannot recommend any reasonably modern introductory references on the topic, but googling "introduction to modern c programming" reveals several promising results. Perhaps other forum-goers can recommend specific reference works.