![df](https://openlab.citytech.cuny.edu/malvarez/files/2014/09/df.png)
df is it displays the amount of disk space available on the filesystem containing each file name argument
![cal](https://openlab.citytech.cuny.edu/malvarez/files/2014/09/cal.png)
cal displays the date so for instance here it shows September 17, 2014
![free](https://openlab.citytech.cuny.edu/malvarez/files/2014/09/free.png)
free displays the amount of memory is being used and not used
![cd](https://openlab.citytech.cuny.edu/malvarez/files/2014/09/cd.png)
cd means change directory allowing the program to change the current working directory in the operating system
![pwd](https://openlab.citytech.cuny.edu/malvarez/files/2014/09/pwd.png)
pwd means what current working directory its on
![ls](https://openlab.citytech.cuny.edu/malvarez/files/2014/09/ls.png)
ls shows command that lists directory contents of files and directories
![file](https://openlab.citytech.cuny.edu/malvarez/files/2014/09/file.png)
file determines which file type it is on
![less](https://openlab.citytech.cuny.edu/malvarez/files/2014/09/less.png)
less allows backward movement in the file as well as forward movement