1. DDaattaa RReepprreesseennttaattiioonn
((iinn ccoommppuutteerr ssyysstteemm))
CCoommppuutteerr FFuunnddaammeennttaall
CCIIMM22446600
BBaavvyy LLII

2. DDaattaa RReepprreesseennttaattiioonn
HHooww ddoo ccoommppuutteerrss rreepprreesseenntt ddaattaa??
Most computers are digital
• Recognize only two discrete states:
on or off
• Computers are electronic devices
powered by electricity, which has only
two states, on or off
1 1 1 1 1
0 0 0 0 0
on
off

3. DDaattaa RReepprreesseennttaattiioonn
WWhhaatt iiss tthhee bbiinnaarryy ssyysstteemm??
A number system that has just two unique digits, 0 and 1
• A single digit is called a bit (binary digit)
• A bit is the smallest unit of data the computer can represent
• By itself a bit is not very informative
The two digits represent the two off and on states
Binary
Digit (bit)
Electronic
Charge
Electronic
State

4. DDaattaa RReepprreesseennttaattiioonn
WWhhaatt iiss aa bbyyttee??
Eight bits are grouped together to form a byte
0s and 1s in each byte are used to represent
individual characters such as letters of the
alphabet, numbers, and punctuation
8-bit byte for the number 3
8-bit byte for the number 5
8-bit byte for the capital letter T

5. DDaattaa RReepprreesseennttaattiioonn
WWhhaatt aarree ttwwoo ppooppuullaarr ccooddiinngg ssyysstteemmss ttoo
rreepprreesseenntt ddaattaa??
American Standard
Code for Information
Interchange (ASCII)
Extended Binary
Coded Decimal
Interchange Code
(EBCDIC)
• Sufficient for
English and
Western European
languages
• Unicode often
used for others

6. DDaattaa RReepprreesseennttaattiioonn
HHooww iiss aa cchhaarraacctteerr sseenntt ffrroomm tthhee kkeeyybbooaarrdd ttoo
tthhee ccoommppuutteerr??
Step 1:
The user presses the letter T key
on the keyboard
Step 2:
An electronic signal for the letter
T is sent to the system unit
Step 3:
The signal for the letter T is
converted to its ASCII binary
code (01010100) and is stored in
memory for processing
Step 4:
After processing, the binary code
for the letter T is converted to an
image on the output device

7. DDaattaa RReepprreesseennttaattiioonn
HHooww iiss aa cchhaarraacctteerr sseenntt ffrroomm tthhee kkeeyybbooaarrdd ttoo
tthhee ccoommppuutteerr??
Step 1:
The user presses the letter T key
on the keyboard
Step 2:
An electronic signal for the letter
T is sent to the system unit
Step 3:
The signal for the letter T is
converted to its ASCII binary
code (01010100) and is stored in
memory for processing
Step 4:
After processing, the binary code
for the letter T is converted to an
image on the output device