There have been a few of us discussing the question you have posted. Generally anything that the reader is required to input (key) into the computer should be transcribed in Computer Braille Code. It has been suggested that computer terms written in a different typeface should be enclosed in CBC symbols. I didn't notice at first, but if you look carefully, you will see that LOWER, UPPER, STEP, #define, getchar, putchar, and printf are in a slightly different typeface. However, the phrase, text stream, seems to be italicized because it is a definition -- is there perhaps a glossary of terms at the end of the book? I would transcribe that phrase as per the rules of italics.
Sorry for the delay in my response! I hope this helps to clarify things for you.