The cluster is the fundamental unit of storage in a file system. It is a collection of sectors on a physical disk.

Cluster Tip

Since the cluster is the fundamental unit of storage in a file system, files which are not sized in a multiple of the cluster size will not fully utilise the clusters allocated to the file. For example, a common cluster size of 4096 bytes. Files using 3000 bytes and 5000 bytes have (4096-3000) = 1096 bytes and (8192-5000) = 3192 bytes of storage allocated to it but left unused. This is the cluster tip.

cluster-tipThe cluster tip holds garbage information (previously-present information) from your system memory and may contain sensitive information. Erasing a drive with an Unused Space erase with Cluster Tip erasure enabled will erase these cluster tips.


This is an acronym for Cryptographically Secure Pseudorandom Number Generator. This is a designation for algorithms which generate random data with patterns indistinguishable from random noise. It is cryptographically secure as it generates “randomness” sufficient for use in salts and key derivation algorithms. It is “Pseudorandom” because the data is generated by a sequence of arithmetic operations.

Erasure Task

The task is the fundamental unit of work that Eraser will complete. A task has associated targets, a schedule, as well as a log to hold errors, warnings and notices encountered during execution.

Erasure Target

The target of an erasure is the set of files or folders which will be erased when the task containing the target is run.

Wildcard expression

A wildcard expression is a specially formed expression which is used to match text. Normal characters appear as-is in a wildcard expression, so these are valid wildcard expressions:

  • File
  • File2.txt

However, they are not really useful as only files matching those names are selected. Therefore, wildcards include the use of two operators, the question mark (?) and the asterisk (*). The question mark means that any character may substitute its place; the asterisk means that any number of characters may substitute its place. Below are examples of wildcard expressions and the file names they match/do not match: underlined letters indicate a match, a words with a strikethrough are mismatches.

Expressions File names matched File names unmatched
* All
Er?se Erase Erroneous Erase
Er*se Eraser Erase
*Erase* Any file name will be Erased

Remember that when using wildcards, most of the time they are applied to file names and file names include the file extension.

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