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Asked: 2026-05-13T21:22:32+00:00

Is it possible to start an array at an index not zero…I.E. you have

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Is it possible to start an array at an index not zero…I.E.
you have an array a[35], of 35 elements, now I want to index at say starting 100, so the numbers would be a[100], a[101], … a[134], is that possible?

I’m attempting to generate a "memory map" for a board and I’ll have one array called SRAM[10000] and another called BRAM[5000] for example, but in the "memory" visibility they’re contiguous, I.E. BRAM starts right after SRAM, so therefore if I try to point to memory location 11000 I would read it see that it’s over 10000 then pass it to BRAM.

While typing this I realized I could I suppose then subtract the 10K from the number and pass that into BRAM, but for the sake of argument, is this possible to index passing 11000 to BRAM?

In the actual architecture I will be implementing, there can/may be a gap between the SRAM and BRAM so for example the address 11008 might not be visible in the memory map, thus writing a giant array full of memory then "partitioning" it will work, but I’ll still have to do logic to determine if it’s within the ranges of "SRAM and BRAM". Which is what I wanted to avoid in the first place.

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1 Answer

  1. Editorial Team

    Is it possible to start an array at an index not zero…I.E. you have an array a[35], of 35 elements, now I want to index at say starting 100, so the numbers would be a[100], a[101], … a[134], is that possible?

    No, you cannot do this in C. Arrays always start at zero. In C++, you could write your own class, say OffsetArray and overload the [] operator to access the underlying array while subtracting an offset from the index.

    I’m attempting to generate a “memory map” for a board and I’ll have one array called SRAM[10000] and another called BRAM[5000] for example, but in the “memory” visiblity they’re contiguous, I.E. BRAM starts right after SRAM, so therefore if I try to point to memory location 11000 I would read it see that it’s over 10000 then pass it to bram.

    You could try something like this:

    char memory[150000];
char *sram = &memory[0];
char *bram = &memory[100000];

    Now, when you access sram[110000] you’ll be accessing something that’s “in bram“

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