Central Processing UnitPart II

Bayram Güzer

Data Representation: On/Off

• Computers are known as complex machines but the reality is they only know two things– ON (electricity turned

on)– OFF (electricity turned

off)

• The two-state on/off system is called as binary system.

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Data Representation: On/Off

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Data Representation: On/Off

• Each 0 or 1 in the binary system is called a bit (binary digit)

• The bit is the basic unit for storing data in computer memory.

• Since single bits by themselves cannot store all the numbers, letters, and special characters, a computer must process the bits together in a group called as byte.

• There are 8 bits in a byte.

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Data Representation: On/Off

• Each byte usually represents one character of data– A letter, digit or special

character.

– There are 8 bits in a byte.

• Capacity of memory and storage are expressed in term of the number of bytes data they can hold.

Binary Character Binary Character

0110000 0 1001001 I

0110001 1 1001010 J

0110010 2 1001011 K

0110011 3 1001100 L

0110100 4 1001101 M

0110101 5 1001110 N

0110110 6 1001111 O

0110111 7 1010000 P

0111000 8 1010001 Q

0111001 9 1010010 R

1000001 A 1010011 S

1000010 B 1010100 T

1000011 C 1010101 U

1000100 D 1010110 V

1000101 E 1010111 W

1000110 F 1011000 X

1000111 G 1011001 Y

1001000 H 1011010 Z

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Data Representation: On/Off

• When number of bytes come together, they are expressed as kilobytes.– It is abbreviated as KB or K.– 1 kilobyte is equal to 1024 bytes.– Ex; Old PC memories.

• A computer word, is defined as the number of bits that constitute a common unit of data, as defined by the computer system.– 32 or 64 bits for most personal computers today.

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Data Representation: On/Off

• When number of kilobytes come together, they are expressed as megabytes.– It is abbreviated as MB which also means 1 million

bytes.– 1 megabyte is equal to 1024 KB.– Ex; Diskette, cd-rom or etc…

• When number of megabytes come together, they are expressed as gigabytes.– It is abbreviated as GB which also means 1 billions of

bytes.– 1 gigabyte is equal to 1024 megabytes.– Ex; Hard disks

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Data Representation: On/Off

• B: Byte b: bit• KB: Kilobyte - Kb: Kilobit• MB: Megabyte - Mb: Megabit• GB: Gigabyte - Gb: Gigabit• 1 B = 8 b (bit)• 1 KB = 1024 B• 1 MB = 1024 KB• 1 GB = 1024 MB

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Data Representation: On/Off

• 1024 KBps --- 1024 Kbps (128 KBps)

• 2048 KBps --- 2048 Kbps (256 KBps)

• 4096 KBps --- 4096 Kbps (512 KBps)

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8-bit Representation ?

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8-bit Representation ?

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Data Representation: On/Off

• It is known that a collection of bits can represent a character of data– But, what particular set of bits is equivalent to

which character?

• There must be an agreement on which groups of bits represent which characters.– ASCII– EBCDIC– Unicode 12

Data Representation: On/Off

• The code called ASCII, which stands for American Standard Code for Information Interchange uses 7-bit for each character which is equivalent to 128 unique combinations.

• A more common version is ASCII-8 which is also called as extended ASCII which can represent 256 different characters.

• ASCII representation has been accepted as universal character representation in computing systems.

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Data Representation: On/Off

• EBCDIC stands for Extended Binary Coded Decimal Interchange Code– It is used primarily on IBM and IBM-compatible

mainframes

• Unicode is designed to accommodate alphabets of more than 256 characters

• Uses 16 bits to represent one character– 65,536 possible values (216)

• Requires twice as much space to store data

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Data Representation: On/OffBinary Character Binary Character

0110000 0 1001001 I

0110001 1 1001010 J

0110010 2 1001011 K

0110011 3 1001100 L

0110100 4 1001101 M

0110101 5 1001110 N

0110110 6 1001111 O

0110111 7 1010000 P

0111000 8 1010001 Q

0111001 9 1010010 R

1000001 A 1010011 S

1000010 B 1010100 T

1000011 C 1010101 U

1000100 D 1010110 V

1000101 E 1010111 W

1000110 F 1011000 X

1000111 G 1011001 Y

1001000 H 1011010 Z15

Hierarchy of Instructions

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Hierarchy of Instructions

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Hierarchy of Instructions

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Hierarchy of Instructions

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References

• Capron, H. L. (2000). Computers Tools for an Information Age.(6th ed.). New Jersey, USA: Prentice Hall.

• http://homepage.cs.uri.edu/faculty/wolfe/book/Readings/Reading04.htm

• http://en.wikipedia.org/wiki/Pulse_%28signal_processing%29• http://www.yale.edu/pclt/PCHW/clockidea.htm• http://www.camiresearch.com/Data_Com_Basics/

data_com_tutorial.html• http://en.wikipedia.org/w/index.php?title=Relational_operator• http://en.wikipedia.org/wiki/Word_(computing)• http://en.wikipedia.org/wiki/32-bit• http://tldp.org/HOWTO/Unix-and-Internet-Fundamentals-

HOWTO/core-formats.html

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