Up until now, we've used what are called "symbolic" modes to specify permission changes to chmod. However, there's another commonly-used way of specifying permissions -- using a 4-digit octal number. Using this syntax, called numeric permissions syntax, each digit represents a permissions triplet. For example, in 1777, the 777 set the 'owner', 'group', and 'other' flags that we've been discussing through this section. The 1 is used to set the special permissions bits, which we'll cover at the end of this section. This chart shows how the second through fourth digits (777) are interpreted: