The extensions on files (which linux does in a poor way, leaving extensions off many types) should tell you something too. You can do a few - like how email virus scanners can recognize most compressed file types - but not all encompassing. There isnt any universal way to detect what the file type is from its first few bytes. There are no 'magic numbers' - these things you see are just integers or doubles or whatever values that mean something: could be the file's size, or the size of the data portion for the image, or the date, or what file version it is (many file types have had revisions and the format varies a little), and so on. Now, all that aside: every file format is different. More often than not the binary is more efficient, though: even for images RBG values may take 3 bytes in text and only 1 in binary, with 245 of 255 values taking more than 1 byte as text. On the flipside, "0" still takes 8 bytes, and only one in text. So binary is harder to read in the hex editor, but saves 11 bytes per integer in this case. In binary though, you see the 8 bytes of the integer (64 bits), 80 00 00 00 00 00 00 00 (or the endian reverse of this). in a hex editor, you see the ascii value in hex for each number as a text value, eg 0x39 0x32 or displayed as 39 32 32. Which is 19 or whatever bytes of data in the file. Say you had this 64 bit integer and wrote it to a file 9223372036854775808 A binary file uses all 0-255 values for any given byte.Ī text file uses a subset of those, the printable characters.
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