There is nothing mysterious about it.
An executable program is a binary file.
A text file is also a binary file.
Essentially, there is not much difference between them.
The particularity of the in.com program lies in that
All the code is entirely distributed within the range of displayable characters in the ASCII code table.
Of course, such a program is not obtained by chance.
But it is artificially constructed.
Many skills are needed in it.
For example, the most common interrupt call code int 21 (CD 21).
Because it is not within the range of displayable ASCII characters.
So many skills such as pushing onto the stack, popping from the stack, and increasing/decreasing code are used to construct it.
So its code segment changes dynamically.
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Such code is called ASCODE.
Such a technology is called ASCII Assemble.
A technology that is about to disappear.
It can be imagined that constructing such code is difficult.
Only a very small amount of ASCODE circulating on the Internet is artificially constructed.
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Because there are mature technologies that can convert any binary file into ASCODE.
Such a process is called encode.
And the execution process of ASCODE requires decode.
Collectively called codec.
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There are more than 4 known algorithms for codec.
The more famous one should be Herbert Kleebauer's algorithm.
But it requires that the original program must have a mark like org 170H.
Because the previous file header is used to store the decode code.
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All this information can be found in usenet.
Of course, it can also be found in google group.
Visiting Herbert Kleebauer's homepage is also a good idea.
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