Here you will find terms used in Digital signal Processing (DSP) with explanations. Please note that the page is still under construction, more terms and explanations will be added over time.

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### Periodic

synonyms: repetitive, cyclic

- Signal or function is periodic, if it consists only of sequence of identical sections. For example sine wave is periodic, exponential decay isn’t.

Facts:

- Device that produces periodic signal is called
*oscillator*.
- Some signals may be
*pseudo-periodic* if they consist of sequence of very similar sections. Common example is a waveform of a plucked string – each next “period” is slightly quieter and has slightly different shape. Such signals may still be analyzed by the same or similar methods (like Fourier Transform or tuner/pitch extractor) like true periodic signals.
- Periodicity may also happen in multiple dimensions where given rectangular/cubic/hypercubic elements occur periodically in all dimensions. Examples are Brick wall (2D) and atomic structure in crystals (3D).

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### Period

- In physics period is a time it takes a periodic signal to repeat it’s pattern exactly once.It is measured in time units (usually seconds) Its reciprocal is the frequency. It is denoted by “
**T**“
- In general it may mean the length of the repeating pattern (not necessarily in time units). For example text may be periodic if it consists of the same sequence of characters repeating over and over- in that case the period is the number of those characters.
- It may also mean the repeating pattern itself (the once instance of repeating section of periodic signal).
- Sometimes period may mean
*wavelength* and vice versa. Although in physics these are quite distinct terms, in case of abstract signal manipulation (digital signal is abstract) the difference between the two is slim.

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### Zero

synonyms: “0”

- A number representing the amount of thing that is absent. As silly as it may seem, representing “nothing” as a number (and thus allowing to perform calculations with it) was a great mathematical breakthrough.
- A representation of “false” in
*boolean *logic. In flowstone green connectors zero in any numeric format is converted to boolean “false” while any other value to “true”
- Common starting position in indexing elements in array. This is done for convenience reasons, because in computers element in array is defined by offset from the first element (thus giving it index of zero).

Interesting and useful facts:

- In computers Zero has common binary structure in most number formats (signed integer, float) which is “all bits off”.
- Zero is neither positive nor negative, but in floating point format every number (including zero) has a sign. Therefore +0 and -0 exist in this format with different binary structures (-0 has first bit on).
- Some mathematic operations cannot be preformed on zero (division by zero, logarithm of zero, etc.). Trying to do so on a computer, various things may happen. Floating point format has special values for
*NaN (not a number) *and both positive and negative *infinity* that may be the result of these operations. Integer formats usually don’t have such special values (giving legit, yet wrong results), but program is notified by processor that this has happened and program may opt to give “error message” (or ignore the fact… like “green” integers in Flowstone).