Language Features
Like Max, Pd is a data flow programming language. As with most DSP software, there are two primary rates at which data is passed: sample (audio) rate, usually at 44,100 samples per second, and control rate, at 1 block per 64 samples. Control messages and audio signals generally flow from the top of the screen to the bottom between "objects" connected via inlets and outlets.
Pd supports 4 basic types of text entities: messages, objects, atoms, and comments. Atoms are the most basic unit of data in Pd, and they consist of either a float, a symbol, or a pointer to a datastructure. (In Pd, all numbers are stored as 32-bit floats). Messages are composed of one or more atoms and provide instructions to objects. A special type of message with null content is called a bang is used to initiate events and push data into flowing, much like pushing a button.
Pd's native objects range from the basic mathematical, logical, and bitwise operators found in every programming language, to general and specialized audio-rate DSP functions (designated by a tilde (~) symbol), such as wavetable oscillators, the Fast Fourier transform (fft~), and a range of standard filters. Data can be loaded from file, read in from an audio board, MIDI, via Open Sound Control (OSC) through a Firewire, USB, or network connection, or generated on the fly, and stored in tables, which can then be read back and used as audio signals or control data.
Read more about this topic: Pure Data
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