It can be noisy and distracting to students to listen to audio speakers when there are multiple computers in the classroom. Headphones help the students
<span>A numeric string is created by a cryptographic
algorithm, which is called a hash that is used to validity of a message or authenticity
of a document. The signature is verified by an algorithm that uses the stated
owner of the signature's public key to accept or reject the authenticity of a
signature. A certification authority's digital signature is used to verify the
authenticity of digital certificates and other documents in a PKI.</span>
XLS would be it, avi contains like sounds and stuff
