AQA GCSE ICT Specification A revision notes (full course)

everything we need to know for the exam tomorrow. hope it helps :)

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1. Computers, data and information
A comp uter
i
s an
information processing machine. Comp u ters process
data to produce information. T he
se t
s o f
i
n str u cti
o n s that
hu ma ns gi
ve
c omp uter
s are
ca ll
ed
programs o r
software. S o ft
w a r
e
that
ca rries out
a
p art
icular
t
yp e
of task for
a
use r
is
oft
e n call
ed
applications software.
Reasons for using computers
C omp ut
ers can w ork mu ch fast
e r
t
h an
huma ns.
C omp ut
ers do no t
g et
t
ired or
ne ed a rest
.
C omp ut
ers can d o j
o bs
that i
t
w ould be da n g ero u s f
or huma n t
o
do.
C omp ut
ers can stor e
lar
g e
a mo unts of
info r
ma t io n
in a
ve ry sma ll
sp ace
C omp ut
ers can fi
n d i
n f
orma ti
on
very q ui
ck l y
C omp ut
ers neve r
lo se
or misplace i
n forma ti
o n.
Three stages of computing:
Input,
processing an d
output
A comp uter
r
u ns t
h r
o ug h t
hes e st
ag es
b y `
run n in g' a program. A
progra m is
a
s et
of st
ep by st
e p i
n struct
ions w hi
ch tell
s the co mp ut
e r
exact l
y what
to do
w i
th
in put
i
n
order
to prod uc e
the r
e quir
e d
o utput.
Input
T his
stage of
comp uti
n g i
s conc er
n ed
w ith get ti
n g
t h e data nee d ed
b y
th e
p rogram onto t
he
c omp ut
er.
Input devices ar e u se d t
o
d o
this. Th e
mo s t
c ommo nl
y used inpu t
d evi
ces a r
e t
h e
mouse a n d keyboard.
Processing
T he i
n st
ruct
ions ab out w hat
to
d o wit
h the
inp u t a r
e contained
in
a program.
D u r
ing t
he process i
n g stage,
the comp ute r
foll ow s t he se i
nstruc ti
on s
us ing
th e
d ata
w hich
has j
u st
b ee n i
npu t
. Wh at
the
comp u t
er pro duces at t
he end of
th i
s
s tage i
s cal
led
output.
Output
T his
stage of
comp uti
n g i
s conc er
n ed
w ith pr
o d u ci
n g the proce s sed
da ta as
in f
orma t
ion i
n a
fo r
m tha t
i
s use f
ul
to
the user. Output devices are used t
o d o
t hi
s.
T he
mo st
co mmo n l
y used ou t
put
d e vi
ces a re t h e screen, w hich
is also
c all
ed a monitor or visual display unit (VDU) a nd t
he
printer.
Data and information
D a t
a i
s any col
lecti
o n o f
numb ers,
chara cters o r ot
h e r
symb ols th at
has been
c oded
int
o a f
orma t t
h at can
b e i
npu t
i
n t
o
a
co mp u t e r
o r
proce ss ed.
D at a on i
ts
o w n
ha s
no me aning
o r
con t
ext. I
t
is
on l
y
a f
te r
p r
oc e ss i
ng by a c omp ute r
t
h a t
d ata
takes on a
c ontex t
and
be come s i
nfo r
ma t i
o n.
T here are
ma ny types o f
dat
a .
A l
l
data e nds u p be in g stored as a ser
ies
o f
n umb ers
insi
d e
the
c omp uter (
b i
nary cod e).
D at a c a n be i
np ut
to t
he co mp ut er
b y t
he
user i
n ma ny differ
e nt
wa ys.
The ma i
n t yp es of
da t
a t
h at can
be i np ut i
nto
a comp ut
er and proc esse d
are numeric,
text, dates, graphics and
sound.
Computer Systems

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Page 2

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Hardware i
s t
he name
that
i
s gi
ven to
an y
pa r
t of
a computer
that you
can
a ct
ua ll
y t
ouch.
An i
n di
vi
d ual
pi
ece of
hardw are
is c al
led
a device. The
basic
h ar
dw ar
e
of
any computer
consist
s of
a central processing unit (CPU) al
ong
w i
th input,
output
a nd
backing storage device s.…read more

Page 3

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The
ke yboard
is
the
mo st
commo n
t
ype of
i
n put
devi
ce .
Ordi
nary
computer
keyboa r
ds have t
heir
keys
ar
ranged i
n
a si
milar
way t
o
those
on a
t
ypew r
it
er.
This
w ay
o f
ar
ranging
the
keys
is
call
ed QWERTY b ecause of
t
he order
that
t
he y
keys appear
in
on
t he
fi
rst
r
ow
of l
ett
e r
s.…read more

Page 4

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A graphics
tabl
e cons i st
s of
a f
lat
su r
f ace
an d
a
pe n,
or
styl
us, w hi
c h
can be
u sed t
o
p roduce
fr
e eh a nd
d r
aw i
ng s o r
t
race aroun d sha pes.…read more

Page 5

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A bar code i
s
a
se t
of
l
i
n e s
o f diff
e r
en t
thi
c knesses that
rep r
e sent
a numb er.
Bar
C o de Rea ders are
u sed
t o
in pu t
d at
a
from b ar
cod es.
Mo st
p rodu c ts
in
sh ops
h ave b ar
cod es on t
he m.…read more

Page 6

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Validation
V ali
dati
o n chec ks are
carri
ed
ou t
by
s of
tware t
o ma ke
s ure t
hat dat
a wh i
c h h as
b een entered i
s
allowable and sensible.
D at
a
that i
s n ot
se nsibl
e
or
all
o w e d
i s
r ej
ected by t
h e comp uter.…read more

Page 7

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Hash total
H a sh t
ota ls
are used t
o check
t ha t
g r
o ups
o f
numb ers
ha ve
been
inp ut
cor rectl
y.
A ha sh
to tal
i
s t
he
sum o f
a
gro up of
n umb e r
s that
are
g oi
ng t
o
be i
n put
.…read more

Page 8

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F ew er key
press es
a r
e need ed
w hen e nte ri
n g
a va l
u e
in t
he f
ie ld
so t
h er
e i
s
l
ess
ch an ce
o f
t
h e wrong keys
b ei
n g
p r
ess ed
T ime
is
sa ved
w h en
en t
eri
ng
da t
a bec a use the r
e is
le ss
t o typ e i…read more

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Me mo r
y w hi
ch is
n ot
wip ed
clean when
t he
comp u t
e r
is turned off
i s
c all
ed nonvolatile memory.
PROM and EPROM
PROM a n d EPROM a r
e
bo t
h
special
typ es of
pro gramma bl
e
re ad
only
me mo ry.
P R OM s ta nd s for Programma ble
Re ad On l
y Me mo r
y.…read more

Page 10

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WORM (
Wr i
te Onc e ,
Re a d Man y)
d i
sks w hi
ch can
ha ve
da t
a wri
tt
e n t
o t
h em
j
u st
on ce.
MagnetoOptical d i
s ks w h ich
ca n have da t
a w r
it
ten t
o them any nu mber of
ti
me s j
u st like a har d
d i
s k.…read more

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