MIS 315 - Bsharah
Digital Data Representation
Class Handout
MIS 315 - Bsharah
Digital Data Representation
• Data Representation Basics
• Representing Numbers, Text, and Pictures
• Quantifying Bits and Bytes
• Circuits and Chips
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MIS 315 - Bsharah
Data Representation
• Data representation refers to the form in which data is
stored, processed, and transmitted.
• Digital devices work with distinct and separate data.
• Analog devices work with continuous data.
• Digitizing is the process of converting analog data
into a digital format.
Digital=Distinct
On / Off
Analog=Continuous
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MIS 315 - Bsharah
Representing Numbers, Characters
(Text), Pictures, and Sound
• Numeric data
– Composed of numbers that might be used in
arithmetic operations.
– Decimal number system has 10 symbols.
– Binary number system has only two
symbols (0, 1).
• Character data
– Composed of letters, symbols, and numerals
that are not used in arithmetic operations.
– ASCII, Extended ASCII, EBCDIC, and
Unicode.
• Picture Data
– Composed of a series of dots.
– Each dot is assigned a binary number for
color.
• Sound Data
– Is characterized by the properties of a sound
wave.
– The wave can be represented digitally by
sampling it a various points and converting
those points into digital numbers.
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MIS 315 - Bsharah
Memory Capacity
• Bit:
– Short for binary digit (0s and 1s), the only data that a CPU
can process.
• Byte:
– An 8-bit string of data, needed to represent any one
alphanumeric character or simple mathematical operation.
In this picture, one byte,
01001000, represents
the letter H
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MIS 315 - Bsharah
Numeric and Character Data
Representation
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MIS 315 - Bsharah
Hierarchy of Memory Capacity
-Quantifying Bits and Bytes
• Bit
– One binary digit
• Byte
– 8 bits
• Kilobyte (KB)
– Approximately one thousand
bytes, (1024 or 210 bytes)
• Megabyte (MB)
– Approximately one million
bytes (1,048,576 bytes, or
1,024 x 1,024 or 220 bytes).
• Gigabyte (GB)
– Actually 1,073,741,824 bytes
(1,024 x 1,024 x 1,024 or 230
bytes).
• Terabyte
– One trillion bytes, or 240
bytes.
• Petabyte
– One thousand terabytes,
or 250 bytes.
• Exabyte
– One thousand petabytes,
or 260 bytes.
• Zettabyte
– One thousand exabytes.
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MIS 315 - Bsharah
Circuits and Chips
• An integrated circuit (computer chip) is a super-thin
slice of semiconducting material packed with
microscopic circuit elements.
– DIP=Dual In-line Package PGA=Pin Grid Array
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MIS 315 - Bsharah
How do bits and bytes fit together with
chips and circuits?
• Bits take the form of
electrical pulses that can
travel over circuits.
– The 1 bit might represent
an elevated voltage, such
as 5 volts, whereas a 0
bit is represented by a
low voltage, such as 0.
• The system board is a
circuit board to which a
multitude of electronic
components are
mounted.
– Motherboard
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MIS 315 - Bsharah
Digital Processing
• Programs and Instruction Sets
• Processor Logic
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MIS 315 - Bsharah
Programs and Instruction Sets
• Computers, portable media players, handheld
computers, and smart phones all work with digital
data.
• Computer programmers create programs that control
digital devices. These programs are usually written in
a high-level programming language.
– The human-readable version of a program created in a highlevel language is called the source code.
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MIS 315 - Bsharah
Programs and Instruction Sets
• The procedure for translating source code into 0’s and 1’s
can be accomplished by a compiler or an interpreter.
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MIS 315 - Bsharah
Programs and Instruction Sets
• A collection of preprogrammed activities a
microprocessor is hardwired to perform is called an
instruction set.
– Additions, subtractions, counting, comparisons, etc
• Each instruction has a corresponding sequence of 0s
and 1s. 00000100 might = Add.
• The list of codes for a microprocessor’s instruction
set, called machine language, can be directly executed
by the processor’s circuitry.
• This end product, the 1s and 0s, is called machine
code.
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MIS 315 - Bsharah
Programs and Instruction Sets
• A machine code instruction has two parts.
– The op code and the operand.
• An op code (short for operation code) is a command
word for an operation such as add, compare, or jump.
• The operand for an instruction specifies the data (or
the address of the data) for the operation.
Op Code
00000100
00000001
00100100
00011001
01010100
00100001
Operand
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MIS 315 - Bsharah
Programs and Instruction Sets
• Many machine language instructions might be needed
to equal a simple high-level program that counts to
100.
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MIS 315 - Bsharah
Processor Logic-What happens inside a
computer chip
• The arithmetic logic unit (ALU) is the part of the
microprocessor that performs arithmetic operations.
• The ALU uses registers to hold data that is being
processed.
• The microprocessor’s control unit fetches each
instruction, just as you get each ingredient out of a
cupboard or the refrigerator.
• The term instruction cycle refers to the process in
which a computer executes a single instruction.
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MIS 315 - Bsharah
Processor Logic-What happens inside a
computer chip
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MIS 315 - Bsharah
Processor Logic-What role does the
Control Unit play
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