how to know the specifications of my machine
 

i need to know the specifications of my machine like harddisk size memory size cach memory and so on ... i need how the commands to do that

$ dmesg|less gives a lot of stuff like that. $ top will give current cache.

For an all-in-one program I'd use lshw.

cat /proc/cpuinfo
hdparm -I /dev/hda
lspci