Simple disk-based sorting method

I have a disk file which contains 370,260 records of average length 60
ASCII text characters. I need to sort them on the first 9 characters,
which are set off from the rest by a space. 

Once sorted the first record looks like
100100100 08:35-08:39 4 0 0 1 -115 -1 75 -100 dd17.txt
and the last one looks like
500900900 12:41-13:25 44 1 885 0 0 1 925 -200 dd21.txt

There is not enough memory in my Win2K/SP4 system to implement the
traditional memory-based sorting algorithms, so I need to use a method
that is disk-file based. I have plenty of disk space.

I imagine that this method would open the input disk file and begin
reading records one at a time and performing some kind of sort
algorithm placing the result in a temporary output file. Once the
original file has been swept, the process starts over and runs again
and again for the required number of iterations until the entire list
is sorted in ascending order. I will implement this method in standard
DOS-based C (Microsoft Optimizing C Compiler "cl") using the Win2K
DVM.

Suggestions and references please.



--

"Nothing in the world can take the place of perseverance. Talent
will not; nothing is more common than unsuccessful men with talent.
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--Calvin Coolidge