The Secure Hash Algorithm (SHA-1) creates:

According to The CISSP Prep Guide, "The Secure Hash Algorithm (SHA-1) computes a fixed length message digest from a variable length input message."

Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, page 160.

also see:

http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf