The MS-DOS COPY command can combine multiple files into one file. When you
issue a command of the following form, COPY switches to ASCII mode and
merges all source files into the target file
COPY <multiple_file_list> <single_file>
where <multiple_file_list> can be of three forms: filenames with "*" or "?"
(wildcard filenames), filenames separated with "+" (a specific, ordered
list of files), or a combination of the two.
Because the COPY command recognizes <single_file> as being an absolute
target, it assumes that you want to concatenate the multiple files into a
single new file. This means that COPY switches to ASCII mode where end-of-
file (EOF) markers are acknowledged.
This behavior is sometimes confusing when you know that only one file
exists that matches the source filename and you formulate a COPY command
that assumes that knowledge. If you issue a command as in the following
example, COPY still switches into merge mode and copies the file as if it
COPY C:\COMM*.* A:\COMMAND.COM
Although you intended to copy only COMMAND.COM from the root of drive C to
the root of drive A, COPY actually tries to concatenate COMMAND.COM with
some other file before it discovers that the some other file does not
exist. The resulting file is shorter than the original because COPY stopped
at the first 0x01A byte that it found. (In the case of COMMAND.COM, this is
usually within the first ten characters, so this particular example occurs