Whats with the zeroes in my binary file?

Question

So. I have been experimenting with fwrite().

On my system sizeof( int ) = 4. I have an array of ints that contains: 1, 2, 3, 4, 5 and 6.

When i write it to a binaryfile and view it with hexdump I get:

0000000 0001 0000 0002 0000 0003 0000 0004 0000
0000010 0005 0000 0006 0000                    
0000018

Whats does it write zeroes between the 4byte values?

Answer 1

Because 1 (for example) represented as 4-byte hex is 00000001. Apparently you're on a little-endian system, hence the apparently back-to-front ordering when you inspect your file.

Answer 2

Your hexdump is grouping two bytes as a single word and changing the endianness. On most systems, using hexdump -C changes the dump into canonical view which prevents the grouping. In hexadecimal, one character represents one nybble, and there are two nybbles per byte. So your 4-byte int should have 8 nybbles in total. Since your numbers are very small, most of your nybbles are 0.