Windows/DOS comes without any convenient method to know how much data is contained within a subdirectory, so I have implemented the obvious algorithm of the Linux/unix "du" (disk usage) program in Windows (and in Linux). The following are available for download:
The source for the du program: du.cpp
The Windows/DOS executable file for the du program du.exe
The Linux ELF executable file for the du program (SuSE/Linux) du
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This implementation uses the short/sweet method of calculating the disk usage from the byte-count of each file. It does not attempt to estimate or calculate the fragmented actual block consumption of each file or directory. Given the current directory, by default, it calculates the usage of all files in and beneath the current directory.