I understand that there are four different primary memory segments that are allocated when a program is loaded into memory: (1) code, (2) data, (3) stack, and (4) extra. Can someone please explain what the extra segment is used for? Thanks in advance.
Extra Segment is generally used for storing the temparory data in various operation (in memcpy( ), to store DS data temporarily.
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Bhupesh
> I understand that there are four different primary memory segments that are allocated
> when a program is loaded into memory:
Only if you're using a 16-bit x86 compiler.
For 32-bit x86 systems, and lots of other platforms, segment registers are nowhere to be found since memory is just a single contiguous address space.
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Ok, so in 16-bit code, the ES segment is NECESSARY to copy from one segment to another, e.g. in a memcpy() where the arguments aren't in the same segment (e.g. global to local variables, variable in the heap, etc).
I don't quite agree with Salem. Yes, segments are not involved in the effective address of the data- or code-access, but the segment registers are actually still needed. It's just that all segments have a base-address of 0 and a size of 4GB (or however large you want the memory to be). So, whilst segments are still there, they are essentially never loaded with different values, just set once and for all in the startup of each process.
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Mats
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