Linux Commands

ls                       list directory contents
cd  xx                change directory to xx. Note, using ".." means change to parent directory
mkdir yy             make a new directpry named yy within the current directory

gcc-6   xx yy     compile/assemble/link the files xx yy together. Executable file is a.out unless option -o is used
        -S             compile only, creating a *.s file for each source file
        -o  zz        specify zz as the name for output file
        -g             set up for debugger
        -O -O1    optimize code
        -O2 -O3   optimize code more and more
        -Og         optimize with debugging

Other information on gcc can be found in the gcc document.