Compared with txt format, CHM format of 1 has the advantages of being easy to read, search and mark on the computer and not easy to be modified. It can be used for text or pictures, or mixed use of pictures and text, and can be opened directly without other auxiliary readers. The disadvantage is that it is not suitable for mobile devices such as mobile phones, and the files are relatively large.

Compared with txt format, 2.exe format is easy to read, search and mark on the computer, and it is not easy to be modified. Can be used for words or pictures, or mixed use of pictures and words, and can be directly opened without other auxiliary readers. Disadvantages are not suitable for mobile devices such as mobile phones, easy to be infected with viruses, and relatively large files.

Compared with txt format, 3.pdf format is easy to read, search and mark on computer, and it is not easy to be modified, so it can be used for text or pictures. But it is not conducive to reading on mobile phones, and the file itself is relatively large, so a reader is needed.