A write-protect is a mechanical or electronic protection device for data carriers such as floppy disks , removable hard disks , audio tapes , video cassettes , minidisc and USB flash drives , which prevents data can be deleted (unintentionally) or modified. The operating system or the software can also provide a file with write protection.
The older 5 ¼ inch floppy disks have a writing notch, which is covered with metal foil for write protection. With 8-inch floppy disks it is the other way round: if the notch is open, the disk is write-protected.
On 3 ½-inch floppy disks, a slide is used as write protection, which closes (writable) or releases (protected) an opening. Many programs supplied on 3½-inch floppy disks have omitted the write-protect slider to save manufacturing costs and prevent accidental erasure of the floppy disk. In this case, the floppy disk can be used after the program is no longer needed by taping over the write protection hole.
In the case of a VHS cassette and also an audio cassette , write protection is implemented by breaking out the tab on the rear long side. A write-protect slide is rarely used on a video cassette. All pre-recorded video or audio cassettes (so-called purchase cassettes ) are write-protected by the manufacturer. Here, too, the write protection can be removed by simply taping over the write protection hole.
This is not possible with write protection implemented internally in terms of hardware. After the data has been successfully saved, the control line for the write authorization is burned through in a controlled manner using an increased current, thus activating the write protection. This is z. B. used in memory and chip cards that contain critical data.
SD and SDHC memory cards have a small plastic slide on the left. If you move the slider towards the contacts, the card is writable, otherwise it is write-protected. The position of the slide is read out by a contact in the card reader.