BASIC INPUT

The basic Input functions operate on streams of characters that by default are taken from the standard input, but can be specified from another stream. The most basic Function is READ.

(READ &Optional input-stream eof-error eof-value )

Reads in the printed representation of a LISP object from the input-stream, builds a corresponding LISP object, and returns the object.

Example: 

(read)
If you type a number, READ will return an atom that represents this number integer o real, if you type a list it will return a similar list, and so on.

BASIC OUTPUT

The basic output functions operate by displaying the resulting on streams of characters to the standard output, that is defined as a default but can be specified to another stream. The most basic Function is PRINT.

(PRINT Object &Optional output-stream )

Output the printed representation of the Object to the Output-stream preceded by a newline. PRIN1 is like PRINT but it does not include the newline. PRINT return as result the Object.

Example: 

(print '(the house ) )
(print 3.14)
There is also a function called FORMAT that produces a very well formatted text.