While in command mode you press "a" : what happens?
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This is an invalid command
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The editor goes in to insert mode and start inserting text after the current cursor location
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The editor searches for charater "a" in the open file
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The editor gives a beep sound
In vi editor command mode, pressing 'a' switches to insert mode and positions the cursor after the current character. The 'a' command is 'append' - it starts inserting text after the current cursor position, as opposed to 'i' (insert) which inserts text before the cursor.
In vim/vi's command mode, the a key stands for 'append' — it switches you into insert mode and places the cursor one character after its current position so you start typing right after the character it was on. This differs from i, which inserts before the cursor. It is not a search command (that's /), so it doesn't look for the literal character 'a' anywhere in the file.