Why should SMS be limited to 70 Chinese characters?

This reason can be traced back to a long time ago. In the 1980s, the bandwidth of wireless transmission was not high, and short messages were required to be concise. In order to meet this requirement, Hillebrand, the inventor of short message, took 160 characters as the upper limit of short message length after the experiment, and could send 160 English letters.

because

English letters are encoded in 7-bit ASCII, while Chinese characters are encoded in 8-bit UCS-2, accounting for 2 bytes, so 160 characters are converted according to 7-bit ASCII encoding, namely

160x7 =1120 bit; Chinese characters are coded according to 8-bit UCS-2, that is, 8 bits are one character and one Chinese character accounts for 2 characters, so the number of Chinese characters converted from 1 120/8 is1/kloc-0.

/2=70。 So short messages are limited to 70 Chinese characters.