Information Technology Reference
In-Depth Information
Freeze/Hang:. When.an.application.freezes,.or.hangs,.it.no.
longer.accepts.any.input,.whether.from.the.keyboard.
or. the. mouse.. Occasionally,. a. frozen. application. will.
return.to.normal..The.problem.may.have.been.related.
to. (say). a. disk. write. command. that. did. not. execute,.
resulting. in. a. time. out,. but. with. control. returned. to.
the.user..Applications.that.freeze.may.also.crash.the.
operating.system,.especially.of.a.PC.
Hardware:. Physical. equipment—processors,. screens,. key-
boards,. mice,. printers,. scanners,. network. routers,.
hubs,. bridges,. racking,. disk. drives,. portable. drives,.
and.so.forth.
Hash (Hashing):. Producing. hash. values. for. accessing. data.
or. for. security.. A. hash. value. (or. simply. hash),. also.
called.a.message.digest,.is.a.number.generated.from.
a.string.of.text..The.hash.is.substantially.smaller.than.
the.text.and.is.generated.by.a.formula.in.such.a.way.
that.it.is.extremely.unlikely.that.some.other.text.will.
produce.the.same.hash.value.
.
. Hashes.play.a.role.in.security.systems.where.they.
are. used. to. ensure. that. transmitted. messages. have.
not.been.tampered.with..The.sender.generates.a.hash.
of. the. message,. encrypts. it,. and. sends. it. with. the.
message.. The. recipient. then. decrypts. both. the. mes-
sage. and.the. hash,. produces. another. hash. from.the.
received. message,. and. compares. the. two. hashes.. If.
they.are.the.same,.there.is.a.very.high.probability.that.
the.message.was.transmitted.intact.
.
. Hashing.is.also.a.common.method.of.accessing.data.
records..Consider,.for.example,.a.list.of.names:
.
.
John.Smith
.
.
Sarah.Jones
.
.
Roger.Adams
.
To. create. an. index,. called. a. hash. table,. for. these.
records,.you.would.apply.a.formula.to.each.name.to.
produce. a. unique. numeric. value.. So. you. might. get.
something.like
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