FORMAT takes at least two arguments, the first being the stream where it sends its output; t is shorthand for the stream *standard-output*.

The second argument to FORMAT is a format string that can contain both literal text and directives telling FORMAT things such as how to interpolate the rest of its arguments 

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;; Prints "1 + 2 = 3" to the standard output and returns ``NIL''.

(format T "1 + 2 = ~d" 3)

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;; Creates and returns a new string containing "1 + 2 = 3".

(format NIL "1 + 2 = ~d" 3)

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