Here are some basic DOS commands which should be helpful to you when you are working (compiling and running code) at the command line.
dir
lists the files and directories in the current directory
cd\
changes the working directory to root of the drive
cd..
changes the working directory to the parent directory
(the one above the current one)
cd [subdirectory]
changes the working directory to the specified child directory
(the one below the current one)
prompt $g
shortens the prompt, you don't see the whole path
prompt $p$g
shows the full path again
cls
clear screen
del [file]
deletes [file] there is no "are you sure?"
ren [old] [new]
renames the file [old] to [new]
Java-specific commands
javac
compiles .java source code
java
runs .class bytecode
