Windows – How to clear the current line of the Windows command prompt

Pressing Ctrl+U will empty the current line.

It's the default kill character on most terminals and it erases the current line (from the cursor to its beginning). The stty command can be used to get or set its value.

[dave@hal9000 ~]$ stty -a
speed 38400 baud; rows 23; columns 75; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = M-^?;
eol2 = M-^?; swtch = M-^?; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
...
[dave@hal9000 ~]$ stty kill ^T # Set it to Ctrl-T

Be the way, werase stands for word erase, so Ctrl+W erases the word on the left of the cursor.

There is a different way to control the history stack, it is not what you wanted but it is a different option you should check out.

In Properties (or Default) when you right click the top left corner there is an option "Discard Old Duplicates" tick it and the stack will change its behavior.

in your example performing "A", "B", "C". and then twice up to perform "B", the stack will look: "B","C","A" (first up will be "B")