You can, but compiler optimizations are free to create invalid results (gcc and msvc won't, but clang will).

char* myArray = malloc(100) - 1; /* now myArray[1] is the first element, and myArray[100] is the last. */ free(myArray + 1); 

But, as other people have mentioned, don't do this. Un-learn your bad habits of starting at 1.

Another solution: Just ignore the first element of the array.