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Contents


• Introduction to Digital Electronics
• Number Systems and Codes
• Algorithm Representation in Pseudocode

Introduction to Digital Electronics

Physical System: control of a boiler

Signals such as pos and temp that can take any
value within a continuous (and thus infinite) set
of values, are called …
ANALOG SIGNALS
Signals such as onoff whose values belong
to a finite set (in this case a 2-element set),
are called…
DIGITAL SIGNALS

Analog vs Digital




Analog Electronics:
An Analog signal is any continuous signal
for which the time varying feature
(variable) of the signal is a representation
of some other time varying quantity, i.e.,
analogous to another time varying signal.
It differs from a digital signal in terms of
small fluctuations in the signal which are
meaningful.
Digital Electronics:
A digital signal uses discrete
(discontinuous) values. By contrast, non-
digital (or analog) systems use a
continuous range of values to represent
information. Although digital
representations are discrete, the
information represented can be either
discrete, such as numbers or letters, or
continuous, such as sounds, images, and
other measurements of continuous
systems.

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Computer Information Representation

Numeration System
Most used systems:



• Decimal system
• Binary system
• Octal system
• Hexadecimal system
Conversion methods will be presented..

Exercise
Compute the decimal representation of the
following binary numbers:
a. 11012
b. 110102
c. 1010012

Exercise
Solution for c. 1010012

Binary System: representation range

Base Conversion (Decimal to Binary)

Exercise
Find Binary Representation of following numbers
a) 4310
b) 5710

Summary


Computer information representation.
Numeration systems (decimal, binary,
hexadecimal).
Pure binary system and representation range.
Base conversion.



Codes

Codes are symbols or group of symbols used to
represent numbers, letters or words.

Morse Code
Morse code uses short and long signals, called
dots and dashes, to represent letters and
numbers. Samuel Morse, an American
scientist, helped developed it to send
messages over long distances using wires,
radios, sound, or light. Messages are sent by
tapping, drumming, buzzing, clicking, or
flashing light.

Binary Coded Decimal Numbers
(BCD)

Binary-coded Decimal or BCD is a way of representing a decimal number as a string
of bits suitable for use in electronic systems. Rather than converting the whole number
into binary, BCD splits the number up into its digits and converts each digit to 4-bit
binary.
BCD was used in some of
the early decimal
computers, and the IBM
System/360 series systems.

Binary Coded Decimal Numbers (BCD)


What is the BCD value for 10?
10 (1+0) = 0001 0000

Question: write BCD values for 12, 19 and 21.

Binary Coded Decimal Numbers (BCD)

Convert(185)10 into BCD and Binary.
Advantages
It can easily be used to drive
displays, as each digit is encoded
separately.
Disadvantages
It is difficult to perform arithmetic
operations (such as adding) on BCD
numbers, as it is not as easy to
recognize carries, etc.
It allows easy conversion to decimal; It is longer than true binary, and so
true binary to decimal conversion is
difficult and gets increasingly
difficult as the number gets longer.
It allows easy scaling by factors of 10
require more storage space.

ASCII Character Code

ASCII is an acronym for American Standard Code for
Information Interchange.
It is a code that uses numbers to represent characters. Each
letter is assigned a number between 0 and 127. A upper and
lower case character are assigned different numbers.
For example the character A is assigned the decimal
number 65, while a is assigned decimal 97.


ASCII Character Code
1. What does ASCII stand for?
a) American Standard Code for Information Interchange
b) American Scientific Code for Information Interchange
c) American Scientific Code for Interchanging Information
d) American Standard Code for Interchanging Information
2. The decimal representation for the character ‘!’ in ASCII is,
a) 31 b) 32 c) 33 d) 34
3. Binary Coding for the letter X is,
a) 01011000
c) 10001000
b) 00111000
d) 00010100

When is ASCII code used?

When a computer sends data the keys you press or the text you send and
receive is sent as a bunch of numbers. These numbers represent the
characters you typed or generated. Because the range of standard ASCII is 0
to 127 it only requires 7 bits or 1 byte of data. For example to send the string
cactus.io as ASCII it would translate to 99 97 99 116 117 115 46 105 111.
Microprocessors only understand bits and bytes. To it everything is a
sequence of bits.


Summary




• Introduction to digital electronics.
• Conversion of numbers; binary to decimal.
• Familiarization with BCD.
• Discussion on ASCII and it’s usage with
practical examples.

ALGORITHM REPRESENTATION
IN PSEUDOCODE

Algorithm representation: pseudocode

• Sequence of operations whose objective is the solution of
some problem such as: complex computation, control of some
process, etc.
• The result of the algorithm execution must be independent of
the chosen type of representation.
• Some common representation methods are: natural language,
pseudocode, flow diagrams and programming languages.


Algorithm

Algorithm representation: pseudocode



 Natural language sentences,
 Programming language instructions,
 Key words that define basic structures
Pseudocode
Similar to programming language but more informal. It uses a mix of

Operations and control structures

Assignments and types of operators

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