How to insert the specified string at the beginning or end of each line in Vi/vim

Header:%s/^/your_word/

End of Line:%s/$/your_word/

Key operation:
Note: Ctrl + V enters column edit mode, moves the cursor down or up, marks the beginning of the line that needs comment, then presses the uppercase I, then inserts the comment, such as "#", and then presses ESC, which is all commented.
Delete: Press v First, enter visual mode, select the number of columns in the landscape (such as "#" comment symbol, need to select two columns), then press ESC, then press CTRL + V to enter the column editing mode, move the cursor down or up, select the comment section, and then press D to delete the note symbol (#).

PS: Of course, it is not necessarily the shell's annotation "#", it can be "//", or any other character; Vim does not know what is an annotation, all characters.

Use the Replace command:
Add a/F comment at the beginning of the entire content
:% s/^/\/\//g
Add a/F comment at the beginning of 2~50
:2,50 s/^/\/\//g
Delete//number at the beginning of 2~50
:2,50 s/^\/\///g

How to insert the specified string at the beginning or end of each line in Vi/vim