When gdb prompts for input, it annotates this fact so it is possible to know when to send output, when the output from a given command is over, etc.
Different kinds of input each have a different input type. Each
input type has three annotations: a pre-
annotation, which
denotes the beginning of any prompt which is being output, a plain
annotation, which denotes the end of the prompt, and then a post-
annotation which denotes the end of any echo which may (or may not) be
associated with the input. For example, the prompt
input type
features the following annotations:
^Z^Zpre-prompt ^Z^Zprompt ^Z^Zpost-prompt
prompt
commands
commands
command. The annotations are repeated for each command which is input.
overload-choice
query
prompt-for-continue
set height 0
to disable
prompting. This is because the counting of lines is buggy in the
presence of annotations.