Cursor
The cursor is the row and column where the next character will be printed or location-sensitive control sequence will be executed.
The cursor is always present in a terminal and is located at some row and column within the active screen area. The cursor may be visually hidden, but the terminal internal state always has a cursor, and it is always located at some active position.
The cursor most commonly is associated with where the next printed character will be placed. However, the cursor is also used for location-sensitive control sequences. For example, when an erase line control sequence is executed, the cursor determines the first line to erase.
The terminal has a single cursor per screen. Note that this document is about the cursor as it relates to the terminal API. Applications such as editors may have their own concept known as a "cursor" that is completely unrelated to the terminal cursor. For example, an editor may support "multiple cursors", but the underlying terminal API is both a separate concept and only supports a single cursor at any given moment.
The cursor is always initially located at the top-left corner of the screen.
The pending wrap state is a boolean value that is set when a character is printed in the rightmost column of the screen to indicate that the next printed character should wrap to the next line.
If the pending wrap state is set, the next printed character will move the cursor to the leftmost column of the next line, unset the pending wrap state, and then print the character1.
The pending wrap state may feel like an obvious and inconsequential feature, but it has a significant (but subtle) impact on cursor behavior. For example, print followed by backspace behaves differently depending on if you're printing in the rightmost column of the screen or not.
If you print a character in any column other than the rightmost column and then send a backspace control character, the cursor will move back on top of the most recently printed character. But if you print a character in the rightmost column and then send a backspace control character, the cursor will move to the left of the character most recently printed. This is the source of bugs in multiple popular shell prompts.
You will see that many control sequences note that they "unset the pending wrap state". This is just as it sounds: if the pending wrap state is set on the cursor, it becomes unset. The next printed character will not wrap to the next line.
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This isn't strictly true. Wraparound modes and scroll regions can change this behavior. ↩