Transcript System Models for Distributed and Cloud Computing

Digital Systems and Information
Dr. Sanjay P. Ahuja, Ph.D.
FIS Distinguished Professor of CIS (2010-2014)
School of Computing, UNF
Digital Systems and Information
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The computer is a digital system. It manipulates discrete
elements of information from the set {0, 1}.
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Discrete information is represented in a digital system by
signals. These signals use two discrete values and
therefore are said to be binary signals (0 or 1, H or L, T or
F).
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The two discrete values are represented by voltage ranges
called HIGH and LOW.
Voltage Ranges for Binary Signals
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Input ranges are larger than output ranges to allow circuits to
function correctly, i.e. recognize logics 1 and 0, in spite of variations
in voltages due to “noise” voltages that may be added/subtracted
from the output voltages.
Information Representation
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Digital computers use the binary number system, which
has two digits, 0 and 1.
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A binary digit is called a bit.
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Example:
(1001)2 represents 9, i.e.
1 x 23 + 0 x 22 + 0 x 21 + 1 x20 = 9
Computer System
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A computer system is composed of hardware and system
software.
The hardware is divided into 3 parts: CPU, main memory,
I/O devices.
Central Processing Unit (CPU) comprises the Arithmetic and Logic Unit (ALU),
registers, control unit (CU), and cache memory (L1 and L2 caches).
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Main memory, also called RAM stores instructions and
data.
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The I/O interface or I/O cards such as graphics cards,
Network interface cards (NICs) etc., contain circuits for
communicating with and controlling the transfer of
information between the computer and the outside
world.
Binary Number System
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Allowed binary digits (bits) are 0 and 1 and the radix or
base = 2.
With 2 bits, we get 22 = 4 combinations: 00, 01, 10, 11.
With n-bits, we get 2n combinations.
With 23, we have 8 combinations:
MSB
000
001
010
011
100
101
110
111
LSB
Base Conversion – Powers of 2
Special Powers of 2
Hexadecimal Number System
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A major numbering system used in digital systems is the hexadecimal
system, also named base 16.
In this system, the numbers are counted
from 0 to 9 and, since in base 16 we
need 16 different symbols, decimal
numbers 10 through 15 are represented
by letters A through F,
respectively. So we go from 0-9, and A-F.