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Textbooks:

1-1 a fundamental question of data compression is "what are we going to compress" and how do you understand that?

Data compression is the signal that signals the source with a minimum of digital representation, reducing the signal space that holds a given message set or collection of data samples. The so-called signal space is the compressed object, refers to: ① physical space, such as memory, disk, tape, optical disk, USB flash drive (CD-ROM) and other data storage media, ② time interval, such as the time required to transmit a given message set, ③ electromagnetic band, such as the transmission of a given message set required by the spectrum, bandwidth, etc. In other words, we want to compress the airspace, time domain and frequency domain space occupied by a certain signal set.

1-2 Another basic problem with data compression is "Why compress", and how do you understand it?

With the development of computer technology, digital technologies (or systems) have many advantages, but also make the data volume increase greatly. The information age brings not only fast and efficient, but also the "explosion", the role of data compression and social benefits, economic benefits will become more and more obvious. Conversely, if data compression is not performed, it can be difficult to practice either transmission or storage. In short, data compression can reduce the amount of data without loss of information, reducing storage space, improve its transmission, storage and processing efficiency of a technical method.

1-6 How is the data compression technology classified?

The classification method of data compression is not uniform. One of the classification methods can be divided into: reversible compression and irreversible compression.

Reference books:

1.4 Items and questions

1. Use the compression tool on your computer to compress different files. Study the effect of the size of the original file on the ratio of the compressed file to the size of the source file.

2, extracts a few paragraphs from a popular magazine, and removes all text that does not affect comprehension, and achieves compression. For example, after deleting is, the, and that, and to my friend in "This is a dog," belongs, you can still pass the same meaning. Measure the redundancy in the text with the ratio of the number of words deleted to the total number of words in the original text, and repeat the experiment with the text in a technical journal. Do we quantitatively discuss the redundancy of text that is excerpted from different sources?

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