how to create a MakeFile in Linux

First in your editor
i am using
vim filename.make
this will open a make file
now

exec:
             ./file
compile: /
fileName.cpp
                   g++ fileName.cpp -o file
                    echo "compilation "
                    touch compile

and press esc key and :wq and
for execution make file use

make -f filename.make

 if in the last no comment after the file name then it will by default called the binary file

make -f filename.make compile


or if we pass "compile" then first its check that if filename.cpp timespan is less then the touch command compile timespan then it will again compile else it will not compile.
and some another things we need to care that after compile: and / there should be a space
and filename.cpp also in the same starting point as the compile: