Understanding Data Representation on Computer Systems

 
INFS 211:
 Introduction to Information Technology
 
Session 2 – 
Data Representation on a Computer System
 
Lecturer: Dr. Ebenezer Ankrah, Dept. of Information Studies
Contact Information: eankrah@ug.edu.gh
 
Session Overview
 
Unlike humans, computer systems work exclusively with numbers
(binary system) to process data into information. Computer systems
need to work in a language they understand. However, the question
is how does the computer convert data into binary system? This
session seeks discuss how data is represented in the computer
system.
 
At the end of the session, the student will
Understand the difference between data and information
Understand how data is converted to information
Understand the binary coding schemes
Be able to covert data into binary forms.
Be able to differentiate between the various elements in the data
hierarchy
 
 
Slide 2
 
Session Outline
 
The key topics to be covered in the session are as
follows:
Binary Digits
Bites and Bytes
Binary Coding Schemes
Data Hierarchy
 
 
 
 
Slide 3
 
Reading List
 
 
Lucas, H. C. (1997). 
Information Technology for Management
(6
th
 ed.)
. R. R. Donnelly & Sons Company. (Chapter 6)
 
Williams, B. K., & Sawyer, S. C. (2014). 
Using Information
Technology: A practical introduction to computers and
communications (11
th
 ed.). 
McGraw-Hill Education.
 (Chapter
4)
 
 
Slide 4
 
BINARY DIGITS
 
Topic One
 
 
Slide 5
 
Binary Digits
 
Data representation on a computer system uses a simple 
on
 or
off
 system. This is usually called a binary system.
 
A computer is
structured in such a way that it operates with devices having only
two states: electric switches which are open or closed; electrical
pulses high or not high; or magnetized elements having one of
two directions or polarities.
 
These two states are represented by 0 or 1 and are referred to as
BINARY DIGITS or BITS. Internally, the microprocessor recognizes
only these two symbols. Documents, photographs, drawings,
recordings of sound or video have to be converted into this 0/1
data before IT can handle them. This conversion process is
known as digitization (i.e. converting into the digits 0 and 1).
 
 
Slide 6
 
Binary Digits
 
Digitized information can be numbers, text, images,
audio or video. Digitization is the key to making use of
information technology. Once information has been
digitized it can be subjected to a wide variety of
manipulations. If information is not digitized, it cannot be
handled by IT.
 
The binary system means that the individual storage unit
of a computer consists of a simple on or off circuit that is
used to represent all types of data on a computer system
no matter how complex it may seem
 
 
Slide 7
 
BITS AND BYTES
 
Topic Two
 
 
Slide 8
 
Bits and Bytes
 
BITS
The numbers 1 and 0 are used to express the two states –
on or off respectively. Any piece of data or instruction must
be coded in these symbols before processing can be done.
Each 1 or 0 in the binary system is a bit.
 
A bit
 
is thus a binary digit of either 0 or 1. A bit is the
smallest unit in which data can be represented on a
computer. The size of a bit is very small. It is ⅛ of a
character.
 
 
Slide 9
 
Bits and Bytes
 
BYTE
A byte is a group of eight bits and is thus equivalent
to a character that can either be a letter, a number or
another symbol.
 
Since a byte has eight bits, there are 2
8
, or 256,
different combinations of (ones) 1s and zeros (0s),
which is sufficient to cover numeric digits, upper and
lower case alphabets, punctuation marks and other
symbols.
 
 
Slide 10
 
Bits and Bytes
 
The capacity of computer memory (primary and
secondary) is determined by the number of bytes it can
hold. Capacity of bytes is usually calculated in kilobytes
(Kb).
 
In this case a kilobyte refers to (1 kilobyte =2
10
 (1024)
bytes. Even though it is customary to assume a kilo being
equivalent to 1000, it is different in the case and actually
equates 1024 bytes.
 
A megabyte (Mb) is equivalent to 2
20
 i. e. (1024x1024)
bytes
 
 
Slide 11
 
Bits and Bytes
 
Gigabyte (Gb) i.e. (1gigabyte = 2
30
 (1048576x1048576) byte)
 
Terabyte (Tb) which is about one trillion bytes.
 
kilobytes (Kb) = 2
10
 (1024) bytes (about 1,000 bytes)
 
megabyte (Mb)  = 2
20
 (1024x1024) bytes (about 1,000,000
bytes)
 
gigabyte (Gb) (1gigabyte = 2
30
 (1048576x1048576) bytes
(about 1,000,000,000 bytes)
 
 
Slide 12
 
BINARY CODING SCHEMES
 
Topic Three
 
 
Slide 13
 
Binary coding schemes
 
Data and instructions are represented electronically with a
binary numbering system. ASCII, EBCDIC, and Unicode are
binary Coding schemes.
 
The decimal system that we are all familiar with has 10
digits (0, 1, 2, 3, 4, 5, 6, 7, 8
, 
9).  The
 
binary system,
however, consists of only two digits - 0 and 1. Each 0 or 1 is
called a bit-short or binary digit.  In the system
 
unit, the 0
can be represented by electricity being off and the 1 by
electricity being on.
 
 
Slide 14
 
Binary coding schemes
 
In order to represent numbers, letters, and special
character, bits are combined into
 
groups of eight bits
called bytes. Each byte typically represents one
character. The characters represented as 0s and 1s
(“off” and “on” electrical states) in the computer
make use of binary coding schemes.
 
Two of the most popular binary coding schemes use
eight bits or one byte. These two coding schemes are
ASCII and EBCDIC. A recently developed code,
Unicode, uses sixteen bits.
 
 
Slide 15
 
Binary coding schemes
 
ASCII
,
 pronounced “as-key,” stands for American
Standard Code for Information Interchange. This is the
most widely used binary code for microcomputers. For
example, the number 3 is represented in ASCII code as
0011 0011.
 
When you press a key on the keyboard, a character is
automatically converted into a series of electronic pulses
that the system can recognise. For example, pressing the
number 3 on a keyboard causes an electronic signal to be
sent to the microcomputer's system unit where it is
converted to the ASCII code of 0011 0011.
 
 
Slide 16
 
Binary coding schemes
 
 
Character 
  
ASCII
A 
   
0100 0001
Q
   
0101 0001
+ 
   
0010 1011
/ 
   
0010 1111
0 
   
0011 0000
9 
   
0011 1001
 
 
Slide 17
 
Binary coding schemes
 
EBCDIC
,
 pronounced “eb-see-dick,” stands for
Extended Binary Coded Decimal Interchange Code. It
was developed by IBM and is used primarily for large
computers. For example, the number 3 is
represented in EBCDIC code as 1111 0011.
 
Unicode
 is a 16-bit code designed to support
international languages like Chinese and Japanese.
These languages have too many characters to be
represented by the eight-bit ASCII and EBCDIC codes.
 
 
Slide 18
 
Binary coding schemes
 
Coding schemes are particularly important to computer
specialists to track down errors and other types of problems.
 
There are several reasons, one of the most important is that
data created by one computer system using one coding
scheme cannot be directly accessed and used by another
computer system using a different coding scheme.
 
Generally, this is not a problem if both computers are
microcomputers since both would most likely use ASCII
 
code.
 
 
Slide 19
 
Binary coding schemes
 
However, problems occur when data is shared
between microcomputers and larger computers that
use EBCDIC code.
 
The data must be translated from one coding scheme
to the other before processing can begin.
Fortunately, special Conversion programs are
available to help with this translation.
 
 
Slide 20
 
DATA HIERARCHY
 
Topic Four
 
 
Slide 21
 
Data hierarchy
 
A bit represents the smallest unit of data a computer can
handle. A group of bits is called a BYTE and represents a
single character, which can be a letter, number or other
symbol.
 
A grouping of characters is called a FIELD. Field is an item of
data about an entity. Terms such as attribute or data
element are sometimes used to represent the same thing
as a field.
 
An entity is any person, place, event or thing about which
data is held.
 
 
Slide 22
 
Data hierarchy
 
Record is a grouping of related data elements that
represents one specific entity. A record forms a single
entry in a file or database.
 
Each record consists of several fields, and shares field
names in common with the other records. File is a
collection of related records.
 
 Database is a well-defined and managed collection of
data. It may consist of a number of related files, for
example student, course, tutor, etc.
 
 
Slide 23
 
Data hierarchy
 
 
 
Slide 24
The data
hierarchy
 
References
 
French, C. S. (2001). 
Data processing and information technology
(10
th
 ed.). London, Continuum: Sage Publications Ltd.
Hutchinson, S. E., & Sawyer, S. C. (2000). 
Computers,
communication and information: A user’s introduction (7
th
 ed.).
Boston: Irwin McGraw-Hill.
O’Leary, T. J. (2004). 
Computing today
. Boston: McGraw Hill.
O’Leary, T. J., & O’Leary, L. I. (2005). 
Computing Essentials
.
Boston: McGraw Hill.
Thompson, R. L., & Cats-Bail, W. L. (2003). 
Information
technology and management (2
nd
 ed.).
 Boston: Irwin McGraw-
Hill.
Williams, et al (2003). 
Using information technology: a practical
introduction of computers and communications
. Boston:
McGraw-Hill.
 
 
Slide 25
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Explore how data is converted into binary forms in computer systems, the difference between data and information, binary coding schemes, and the elements of the data hierarchy. Learn about binary digits, bites, bytes, and the essential topics covered in this educational session. Recommended reading materials for further understanding are also provided.


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  1. Data Representation on a Computer System Lecturer: Dr. Ebenezer Ankrah, Dept. of Information Studies Contact Information: eankrah@ug.edu.gh College of Education School of Continuing and Distance Education 2014/2015 2016/2017

  2. Session Overview Unlike humans, computer systems work exclusively with numbers (binary system) to process data into information. Computer systems need to work in a language they understand. However, the question is how does the computer convert data into binary system? This session seeks discuss how data is represented in the computer system. At the end of the session, the student will Understand the difference between data and information Understand how data is converted to information Understand the binary coding schemes Be able to covert data into binary forms. Be able to differentiate between the various elements in the data hierarchy Slide 2

  3. Session Outline The key topics to be covered in the session are as follows: Binary Digits Bites and Bytes Binary Coding Schemes Data Hierarchy Slide 3

  4. Reading List Lucas, H. C. (1997). Information Technology for Management (6th ed.). R. R. Donnelly & Sons Company. (Chapter 6) Williams, B. K., & Sawyer, S. C. (2014). Using Information Technology: A practical introduction to computers and communications (11th ed.). McGraw-Hill Education. (Chapter 4) Slide 4

  5. Topic One BINARY DIGITS Slide 5

  6. Binary Digits Data representation on a computer system uses a simple on or off system. This is usually called a binary system.A computer is structured in such a way that it operates with devices having only two states: electric switches which are open or closed; electrical pulses high or not high; or magnetized elements having one of two directions or polarities. These two states are represented by 0 or 1 and are referred to as BINARY DIGITS or BITS. Internally, the microprocessor recognizes only these two symbols. Documents, photographs, drawings, recordings of sound or video have to be converted into this 0/1 data before IT can handle them. This conversion process is known as digitization (i.e. converting into the digits 0 and 1). Slide 6

  7. Binary Digits Digitized information can be numbers, text, images, audio or video. Digitization is the key to making use of information technology. Once information has been digitized it can be subjected to a wide variety of manipulations. If information is not digitized, it cannot be handled by IT. The binary system means that the individual storage unit of a computer consists of a simple on or off circuit that is used to represent all types of data on a computer system no matter how complex it may seem Slide 7

  8. Topic Two BITS AND BYTES Slide 8

  9. Bits and Bytes BITS The numbers 1 and 0 are used to express the two states on or off respectively. Any piece of data or instruction must be coded in these symbols before processing can be done. Each 1 or 0 in the binary system is a bit. A bitis thus a binary digit of either 0 or 1. A bit is the smallest unit in which data can be represented on a computer. The size of a bit is very small. It is of a character. Slide 9

  10. Bits and Bytes BYTE A byte is a group of eight bits and is thus equivalent to a character that can either be a letter, a number or another symbol. Since a byte has eight bits, there are 28, or 256, different combinations of (ones) 1s and zeros (0s), which is sufficient to cover numeric digits, upper and lower case alphabets, punctuation marks and other symbols. Slide 10

  11. Bits and Bytes The capacity of computer memory (primary and secondary) is determined by the number of bytes it can hold. Capacity of bytes is usually calculated in kilobytes (Kb). In this case a kilobyte refers to (1 kilobyte =210 (1024) bytes. Even though it is customary to assume a kilo being equivalent to 1000, it is different in the case and actually equates 1024 bytes. A megabyte (Mb) is equivalent to 220 i. e. (1024x1024) bytes Slide 11

  12. Bits and Bytes Gigabyte (Gb) i.e. (1gigabyte = 230 (1048576x1048576) byte) Terabyte (Tb) which is about one trillion bytes. kilobytes (Kb) = 210 (1024) bytes (about 1,000 bytes) megabyte (Mb) = 220 (1024x1024) bytes (about 1,000,000 bytes) gigabyte (Gb) (1gigabyte = 230 (1048576x1048576) bytes (about 1,000,000,000 bytes) Slide 12

  13. Topic Three BINARY CODING SCHEMES Slide 13

  14. Binary coding schemes Data and instructions are represented electronically with a binary numbering system. ASCII, EBCDIC, and Unicode are binary Coding schemes. The decimal system that we are all familiar with has 10 digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9). Thebinary system, however, consists of only two digits - 0 and 1. Each 0 or 1 is called a bit-short or binary digit. In the systemunit, the 0 can be represented by electricity being off and the 1 by electricity being on. Slide 14

  15. Binary coding schemes In order to represent numbers, letters, and special character, bits are combined intogroups of eight bits called bytes. Each byte typically represents one character. The characters represented as 0s and 1s ( off and on electrical states) in the computer make use of binary coding schemes. Two of the most popular binary coding schemes use eight bits or one byte. These two coding schemes are ASCII and EBCDIC. A recently developed code, Unicode, uses sixteen bits. Slide 15

  16. Binary coding schemes ASCII,pronounced as-key, stands for American Standard Code for Information Interchange. This is the most widely used binary code for microcomputers. For example, the number 3 is represented in ASCII code as 0011 0011. When you press a key on the keyboard, a character is automatically converted into a series of electronic pulses that the system can recognise. For example, pressing the number 3 on a keyboard causes an electronic signal to be sent to the microcomputer's system unit where it is converted to the ASCII code of 0011 0011. Slide 16

  17. Binary coding schemes Character A Q + / 0 9 ASCII 0100 0001 0101 0001 0010 1011 0010 1111 0011 0000 0011 1001 Slide 17

  18. Binary coding schemes EBCDIC,pronounced eb-see-dick, stands for Extended Binary Coded Decimal Interchange Code. It was developed by IBM and is used primarily for large computers. For example, the number 3 is represented in EBCDIC code as 1111 0011. Unicode is a 16-bit code designed to support international languages like Chinese and Japanese. These languages have too many characters to be represented by the eight-bit ASCII and EBCDIC codes. Slide 18

  19. Binary coding schemes Coding schemes are particularly important to computer specialists to track down errors and other types of problems. There are several reasons, one of the most important is that data created by one computer system using one coding scheme cannot be directly accessed and used by another computer system using a different coding scheme. Generally, this is not a problem if both computers are microcomputers since both would most likely use ASCIIcode. Slide 19

  20. Binary coding schemes However, problems occur when data is shared between microcomputers and larger computers that use EBCDIC code. The data must be translated from one coding scheme to the other before processing can begin. Fortunately, special Conversion programs are available to help with this translation. Slide 20

  21. Topic Four DATA HIERARCHY Slide 21

  22. Data hierarchy A bit represents the smallest unit of data a computer can handle. A group of bits is called a BYTE and represents a single character, which can be a letter, number or other symbol. A grouping of characters is called a FIELD. Field is an item of data about an entity. Terms such as attribute or data element are sometimes used to represent the same thing as a field. An entity is any person, place, event or thing about which data is held. Slide 22

  23. Data hierarchy Record is a grouping of related data elements that represents one specific entity. A record forms a single entry in a file or database. Each record consists of several fields, and shares field names in common with the other records. File is a collection of related records. Database is a well-defined and managed collection of data. It may consist of a number of related files, for example student, course, tutor, etc. Slide 23

  24. Data hierarchy Bit Byte Field The data hierarchy Record File Database Slide 24

  25. References French, C. S. (2001). Data processing and information technology (10th ed.). London, Continuum: Sage Publications Ltd. Hutchinson, S. E., & Sawyer, S. C. (2000). Computers, communication and information: A user s introduction (7th ed.). Boston: Irwin McGraw-Hill. O Leary, T. J. (2004). Computing today. Boston: McGraw Hill. O Leary, T. J., & O Leary, L. I. (2005). Computing Essentials. Boston: McGraw Hill. Thompson, R. L., & Cats-Bail, W. L. (2003). Information technology and management (2nd ed.). Boston: Irwin McGraw- Hill. Williams, et al (2003). Using information technology: a practical introduction of computers and communications. Boston: McGraw-Hill. Slide 25

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