Overwriting is the rewriting or replacing of files and other data in a computer system or database with new data. One common example of this is receiving an alert in Microsoft Word that a file with the same name already exists and being prompted to choose whether you want to restore the old file or save the new one. Saving the new one will overwrite the previous file, even if that save is as innocuous as changing the title or retaining it.

The details of the overwriting process are complicated, but they involve the switching of binary 0s and 1s in code, an often irreversible process. Some computer systems allow file recovery or retrieval with certain conditions that must be met. Backing up files to a cloud is a good way to have previous versions of files available, so that a previous version can be restored if needed.

Some applications, such as Microsoft Word, have two different typing modes — overwrite (or overtype) mode and insert mode. Insert mode is by far the more used; you simply add new data by typing wherever your mouse clicks. But overwrite mode replaces data as you type. This is a setting you have to select within the application if you want to use it.

Overwriting and security

It sounds difficult to retrieve or retain data if it’s accidentally overwritten, and it is. But ironically, fully and completely overwriting data in file systems and hardware can be challenging. Companies or individuals often want to completely overwrite a file or device so that no sensitive data is left on it when they transfer it to someone else. But some systems create new backups in different areas that users don’t know about — for the purpose of rescuing that data should it be lost — and then they can’t fully wipe a file or device. Solid state drives (SSDs), for example, sometimes retain or duplicate data in storage, which makes it hard to get rid of that data when needed. Many devices that were supposed to be wiped of all previous data haven’t actually been cleared. This is a potential security hazard.

Also see overwrite mode

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