Description
Program Design
A fundamental concept in DBMS is the table. A table consists of zero or
more records or entries, and each record can have one or more fields or
columns. An example of a table that stores information about music albums is shown below:
id title year artist
10 The Dark Side of the Moon 1973 Pink Floyd
14 Back in Black 1980 AC/DC
23 Their Greatest Hits 1976 Eagles
37 Falling into You 1996 Celine Dion
43 Come Away With Me 2002 Norah Jones
55 21 2011 Adele
This table contains 6 records. Each record has 4 fields, namely, id, title,
year, and artist.
In this assignment, you will focus on implementing a single database
table with 4 fields (id, title, year, and artist). To guide you in the implementation, a high-level design of the table is shown below:
The design consists of a C++ class and an array of structures. The C++ class
should have the following member variables:
• table: a pointer to an array of structures that is dynamically allocated
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NWEN 241 2019-T1 “Database Management System” Assignment 3
• rowsTotal: the total number of rows in the array of structures
• rowsUsed: the number of rows in the array of structures that contains valid records.
The array of structures will hold the records. This array should be dynamically adjusted using the following scheme:
• Upon instantiation of the class, memory should be dynamically allocated for holding 5 records. rowsTotal should be set to 5 and
rowsUsed should be set to 0.
• When adding a record and there is unused space in the table (rowsUsed
is less than rowsTotal), the record is stored in the next unused row,
and rowsUsed is updated accordingly.
• When adding a record and there is no space in the table (rowsUsed
is equal to rowsTotal), additional memory for holding 5 records
should be allocated. Then, the record is stored in the next unused
row, and rowsUsed and rowsTotal are updated accordingly.
• When removing a record, records after the removed record should be
moved up by one row so that there will be no gaps in between used
rows. When the number of unused rows reaches 5, the unused rows
should be released, and rowsUsed and rowsTotal are updated accordingly. When removing the last remaining record, do not release
the remaining unused rows.
• Upon destruction of the class, allocated memory should be freed.
Task 1.
Basics [15 Marks]
In this task, you will declare a C structure for holding one (1) table record.
The structure should have a tag album with the following members:
• id: an unsigned long integer
• title: an array of characters with length 100
• year: an unsigned short integer
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NWEN 241 2019-T1 “Database Management System” Assignment 3
• artist: an array of characters with length 100
The structure should be defined within dbms namespace.
Save the structure in a header file named dbms.hh.
Task 2.
Basics [15 Marks]
Declare a C++ class for holding information about the table, as well as supporting table operations specified in Tasks 5–7. The class should be named
DbTable and should be defined within dbms namespace.
Minimally, the class should have member variables table, rowsTotal,
and rowsUsed as described in the Program Design section. These variables
should be unsigned integers and should be private.
In addition to the member functions specified in Tasks 5–7, the class should
have the following public member functions that are defined inline:
• A function named rows() which should return rowsUsed.
• A function named allocated() which should return rowsTotal.
You may declare additional member variables and functions needed by
your implementations.
Save the class in a header file named dbms.hh.
Task 3.
Basics [15 Marks]
Provide an implementation of the default constructor for the DbTable class.
As mentioned in the Program Design section, during instantiation, memory should be dynamically allocated for holding 5 records. Use either
malloc() or calloc() for this purpose.
Save the implementation in dbms.cc.
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NWEN 241 2019-T1 “Database Management System” Assignment 3
Task 4.
Completion [15 Marks]
Provide an implementation of a destructor for the DbTable class.
As mentioned in the Program Design section, during destruction, allocated
memory should be freed.
Save the implementation in dbms.cc.
Task 5.
Completion [15 Marks]
Provide an implementation of a member function for displaying the information stored in a row. You are free to format the print out, but all fields of
the row should be displayed. The function should be called show() and
should take an unsigned integer as parameter. This parameter indicates the
row number of the record to be displayed.
If the record exists, the function should return true, otherwise, it should
return false.
Task 6.
Completion [15 Marks]
Provide an implementation of a member function for a adding a record
into the database table. The function should be called add() and should
take a reference to album structure as input parameter. The input parameter
contains the record details to be stored in the table.
As mentioned in the Program Design section:
• When adding a record and there is unused space in the table (rowsUsed
is less than rowsTotal), the record is stored in the next unused row,
and rowsUsed is updated accordingly.
• When adding a record and there is no space in the table (rowsUsed
is equal to rowsTotal), additional memory for holding 5 records
should be allocated. Then, the record is stored in the next unused
row, and rowsUsed and rowsTotal are updated accordingly.
The function should always return true unless the allocation of additional
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NWEN 241 2019-T1 “Database Management System” Assignment 3
memory (when needed) fails.
Task 7.
Challenge [10 Marks]
Provide an implementation of a member function for a removing a record
from the database table. The function should be called remove() and
should take an unsigned long integer as input parameter. The input parameter specifies the id of the record to be removed.
As mentioned in the Program Design section:
• When removing a record, records after the removed record should be
moved up by one row so that there will be no gaps in between used
rows. When the number of unused rows reaches 5, the unused rows
should be released, and rowsUsed and rowsTotal are updated accordingly. When removing the last remaining record, do not release
the remaining unused rows.
The function should return true if the removal was successful, otherwise,
it should return false.
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NWEN 241 2019-T1 “Database Management System” Assignment 3
Marking Criteria for Tasks 3–7:
Criteria Weight Expectations for Full Marks
“Compilability” 10% Source code compiles without warnings
Commenting 10% Source code contains sufficient and appropriate
comments
Coding Style 10% Source code is formatted, readable and uses a
coding style consistently
Dynamic Memory Allocation
30% Uses the specified dynamic memory allocation
functions correctly
Correctness 40% Handles all possible cases correctly
100%
Marking Criteria for Tasks 1 and 2:
Criteria Weight Expectations for Full Marks
Commenting 10% Source code contains sufficient and appropriate
comments
Coding Style 10% Source code is formatted, readable and uses a
coding style consistently
Correctness 40% Addresses all specifications and correctly uses
syntax in the declarations and/or definitions
Completeness 40% Declaration and/or definition of all required
members
100%
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