I don't have time for a full review at the moment but something (削除) filled me with rage (削除ここまで) jumped out at me...

#Naming

The code should be readable - you have 2 ways of making that the case, one is by naming things correctly (the second is formatting).

So when I see things like this:

int a = 0, ac, b=-1, li = 0; // a = current folder marker, ac = current file placeholder, b = loop condition, li = Log counter
string cfile; // Current file name

Well, I won't go in to how it makes me feel.

If ac is the current file why don't you call it currentFile. Then when you're doing things with the current file, I won't have to scroll back to the top to figure out what ac is.

Try to name local variables in camelCase: logpath should be logPath.

What is dirf?!

Classes should be PascalCase like DateTime, FileInfo etc.

Stop abbreviating things because I promise that even you won't remember what they meant when you read them back in a week, let alone a year.

I don't have time for a full review at the moment but something (削除) filled me with rage (削除ここまで) jumped out at me...

Naming

The code should be readable - you have 2 ways of making that the case, one is by naming things correctly (the second is formatting).

So when I see things like this:

int a = 0, ac, b=-1, li = 0; // a = current folder marker, ac = current file placeholder, b = loop condition, li = Log counter
string cfile; // Current file name

Well, I won't go in to how it makes me feel.

If ac is the current file why don't you call it currentFile. Then when you're doing things with the current file, I won't have to scroll back to the top to figure out what ac is.

Try to name local variables in camelCase: logpath should be logPath.

What is dirf?!

Classes should be PascalCase like DateTime, FileInfo etc.

Stop abbreviating things because I promise that even you won't remember what they meant when you read them back in a week, let alone a year.