Updated April 10, 2017. In grammar, a demonstrative is a determiner or a pronoun that points to a particular noun or to the noun it replaces. There are four demonstratives in English: the near demonstratives this and these, and the far demonstratives that and those. This and that are singular; these and those are plural.
In the context of video compression, codec is a concatenation of encoder and decoderâa device that only compresses is typically called an encoder, and one that only decompresses is a decoder. The compressed data format usually conforms to a standard video compression specification.
In the mid 20th century, a codec was a device that coded analog signals into digital form using pulse-code modulation (PCM). Later, the name was also applied to software for converting between digital signal formats, including compander functions. A modem is a contraction of modulator-demodulator.