Each pane of the Text Compare view is a full-featured text editor. You can enter and edit text like any other text editor, although as you do the comparison is continually updated to reflect differences between the panes.
Visible whitespace
Enabling the Visible Whitespace 
command allows you to see where spaces, tabs, and line endings occur in your files. The following example illustrates each of them.
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Space |
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Tab |
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Windows line ending |
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Mac line ending |
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Unix line ending |
Editing disabled
Beyond Compare disables editing of a file for any of the following reasons:
•The comparison encountered an error.
•The comparison was cancelled.
•The location of the file is read-only (e.g. 7zip/CHM/RAR archives, CD-ROMs, DVD-ROMs).
•The file format conversion doesn't support saving.
•Editing in the parent folder session has been disabled.
•Editing in the file session has been disabled.
•Command line switches have disabled editing.
