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Memory for large arrays in cygwin/g77

Using cygwin/g77, I was happy with a memory limitation of something over 240
Mb when I was using a laptop with 64 Mb of physical memory. However, I
recently acquired a new PC with 512 Mb of physical memory and found that the
memory available for array allocation did not increase, remaining little
over 240 Mb. The same phenomenon occurs with f2c as with g77. I can do a
little better in straight C, with something over 600 Mb available on the new
computer, but only by declaring the arrays dynamically. What is going on? (I
am not a programmer, just a number cruncher.)

I have explored accessible memory by means of the subsequent test program,
edited in several obvious ways.

implicit double precision (a-h,o-z)
c ny=300 works (240 Mb), 400 doesnt (message about heap)
dimension a(nx,ny)
c dimension a1(nx,ny)
write(6,*) 'megabytes= ',nx*ny*8/1d6
write(6,*) 'extremes initialized'

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