Original sentence: Control characters may be described as doing something when the user inputs them, such as code 3 (End-of-Text character, ETX, ) to interrupt the running process, or code 4 (End of transmission, EOT, ), used to end text input or to exit a Unix shell
Edited sentence: You may often see control characters described as doing something when the user inputs them, such as code 3 (End-of-Text character, ETX, ) to interrupt the running process, or code 4 (End of transmission, EOT, ), used to end text input or to exit a Unix shell