In computing, the SEX assembly language mnemonic has often been used for the "Sign EXtend" machine instruction found in the Motorola 6809.
[2] Functions are sometimes needed for computers of different endianness to communicate with each other over the internet, as protocols often use big endian byte coding by default.
[3][4] On the RCA 1802 series of microprocessors, the SEX, for "SEt X," instruction is used to designate which of the machine's sixteen 16-bit registers is to be the X (index) register.
As file sharing has sometimes spread computer viruses, it has been stated that “illicit SEX can transmit viral diseases to your computer.” The involvement of FTP servers' /pub directories in this process has led to the name being explained as a contraction of 'pubic'.
This article is based in part on the Jargon File, which is in the public domain.