Epson 3865X Plus User Manual page 84

To write-protect a 5 '/+inch diskette, cover the small,
rectangular notch (shown below) with an adhesive write-
protect tab. Write-protect tabs usually are included in a new
package of blank 5 %-inch diskettes.
kite-protect
notch
To remove the write protection, peel off the write-protect tab.
Note
MS-DOS diskettes
Some program diskettes, such as your and
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Using Your Computer