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Computer Science > Chapter 9. Algorithm Design and Problem Solving > Flashcards

Chapter 9. Algorithm Design and Problem Solving Flashcards

1
Q

Comments

A

// This is a comment

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2
Q

Datatypes

A
  • INTEGER a whole number
  • REAL a number capable of containing a fractional part
  • CHAR a single character
  • STRING a sequence of zero or more characters
  • BOOLEAN the logical values TRUE and FALSE
  • DATE a valid calendar date
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3
Q

Literals

A
  • Integer Written as normal in the denary system, e.g. 5, –3
  • Real Always written with at least one digit on either side of the decimal point, zeros being added if
    necessary, e.g. 4.7, 0.3, –4.0, 0.0
  • Char A single character delimited by single quotes e.g. ꞌxꞌ, ꞌCꞌ, ꞌ@ꞌ
  • String Delimited by double quotes. A string may contain no characters (i.e. the empty string)
    e.g. “This is a string”, “”
  • Boolean TRUE, FALSE
  • Date This will normally be written in the format dd/mm/yyyy. However, it is good practice to state
    explicitly that this value is of data type DATE and to explain the format (as the convention for
    representing dates varies across the world).
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4
Q

Variable declarations

A

DECLARE <identifier> : <data>
DECLARE Counter : INTEGER
DECLARE TotalToPay : REAL
DECLARE GameOver : BOOLEAN</data></identifier>

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5
Q

Constants

A

CONSTANT <identifier> = <value>
CONSTANT HourlyRate = 6.50
CONSTANT DefaultText = "N/A"</value></identifier>

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6
Q

Assignments

A

<identifier> ← <value>
Counter ← 0
Counter ← Counter + 1
TotalToPay ← NumberOfHours * HourlyRate
</value></identifier>

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7
Q

Declaring arrays

A

A one-dimensional array is declared as follows:
DECLARE <identifier>:ARRAY[<lower>:<upper>] OF <data>
A two-dimensional array is declared as follows:
DECLARE <identifier>:ARRAY[<lower1>:<upper1>,<lower2>:<upper2>] OF <data>
Example – array declarations
DECLARE StudentNames : ARRAY[1:30] OF STRING
DECLARE NoughtsAndCrosses : ARRAY[1:3,1:3] OF CHAR</data></upper2></lower2></upper1></lower1></identifier></data></upper></lower></identifier>

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8
Q

Using arrays

A

StudentNames[1] ← “Ali”
NoughtsAndCrosses[2,3] ← ꞌXꞌ
StudentNames[n+1] ← StudentNames[n]
FOR Index ← 1 TO 30
StudentNames[Index] ← “”
NEXT Index

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9
Q

Defining user-defined data types

A

Non-composite-Enumerated data types
TYPE <identifier> = (value1, value2, value3, ...)
TYPE Season = (Spring, Summer, Autumn, Winter)</identifier>

Pointer data types
TYPE TIntPointer = ^INTEGER
DECLARE MyPointer : TIntPointer

Composite datatype-Record
TYPE <identifier1>
DECLARE <identifier2> : <data>
DECLARE <identifier3> : <data>
...
ENDTYPE</data></identifier3></data></identifier2></identifier1>

TYPE StudentRecord
DECLARE LastName : STRING
DECLARE FirstName : STRING
DECLARE DateOfBirth : DATE
DECLARE YearGroup : INTEGER
DECLARE FormGroup : CHAR
ENDTYPE

Set
TYPE <identifier1> = SET OF <data>
DEFINE <identifier2> (value1, value2, value, … ) : <identifier1></identifier1></identifier2></data></identifier1>

TYPE LetterSet = SET OF CHAR
DEFINE Vowels (‘A’,’E’,’I’,’O’,’U’): LetterSet

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10
Q

Using user defined data types

A

DECLARE Pupil1 : StudentRecord
DECLARE Pupil2 : StudentRecord
DECLARE Form : ARRAY[1:30] OF StudentRecord
DECLARE ThisSeason : Season
DECLARE NextSeason : Season
DECLARE MyPointer : TIntPointer
Pupil1.LastName ← “Johnson”
Pupil1.Firstname ← “Leroy”
Pupil1.DateOfBirth ← 02/01/2005
Pupil1.YearGroup ← 6
Pupil1.FormGroup ← ꞌAꞌ
Pupil2 ← Pupil1
FOR Index ← 1 TO 30
Form[Index].YearGroup ← Form[Index].YearGroup + 1
NEXT Index
ThisSeason ← Spring
MyPointer ← ^ThisSeason
NextSeason ← MyPointer^ + 1
// access the value stored at the memory address

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11
Q

Input and output

A

INPUT <identifier>
OUTPUT <value(s)>
INPUT Answer
OUTPUT Score
OUTPUT "You have ", Lives, " lives left"</identifier>

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12
Q

Arithmetic operations

A

+ Addition
– Subtraction
* Multiplication
/ Division (The resulting value should be of data type REAL, even if the operands are integers.)
DIV Integer division: Used to find the quotient (integer number before the decimal point) after division.
MOD or Modulus: The remainder that is left over when one number is divided by another

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13
Q

Relational operations

A

> Greater than
< Less than
= Greater than or equal to
<= Less than or equal to
= Equal to
<> Not equal to
The result of these operations is always of data type BOOLEAN.

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14
Q

String functions and operations

A

RIGHT(ThisString : STRING, x : INTEGER) RETURNS STRING
returns rightmost x characters from ThisString
Example: RIGHT(“ABCDEFGH”, 3) returns “FGH”
LENGTH(ThisString : STRING) RETURNS INTEGER
returns the integer value representing the length of ThisString
Example: LENGTH(“Happy Days”) returns 10
MID(ThisString : STRING, x : INTEGER, y : INTEGER) RETURNS STRING
returns a string of length y starting at position x from ThisString
Example: MID(“ABCDEFGH”, 2, 3) returns “BCD”
LCASE(ThisChar : CHAR) RETURNS CHAR
returns the character value representing the lower-case equivalent of ThisChar
If ThisChar is not an upper-case alphabetic character, it is returned unchanged.
Example: LCASE(ꞌWꞌ) returns ꞌwꞌ
UCASE(ThisChar : CHAR) RETURNS CHAR
returns the character value representing the upper-case equivalent of ThisChar
If ThisChar is not a lower-case alphabetic character, it is returned unchanged.
Example: UCASE(ꞌhꞌ) returns ꞌHꞌ
In pseudocode, the operator & is used to concatenate (join) two strings.
Example: “Summer” & “ “ & “Pudding” produces “Summer Pudding”

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15
Q

Numeric functions

A

INT(x : REAL) RETURNS INTEGER
returns the integer part of x
Example: INT(27.5415) returns 27
RAND(x : INTEGER) RETURNS REAL
returns a random real number in the range 0 to x (not inclusive of x)
Example: RAND(87) may return 35.43

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16
Q

If statements

A

IF <condition> THEN
<statement(s)>
ENDIF
IF <condition> THEN
<statement(s)>
ELSE
<statement(s)>
ENDIF</condition></condition>

*There are no elseif statements you have to use case or nest if statements

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17
Q

CASE statements

A

CASE OF <identifier>
<value 1> : <statement1></statement1></identifier>

<statement2>
...
<value 2> : <statement1>
<statement2>
...
OTHERWISE : <statement1>
<statement2>
...
ENDCASE

Each value may be represented by a range, for example:
<value1> TO <value2> : <statement1>
<statement2>

INPUT Move
CASE OF Move
ꞌWꞌ : Position ← Position − 10
ꞌSꞌ : Position ← Position + 10
ꞌAꞌ : Position ← Position − 1
ꞌDꞌ : Position ← Position + 1
OTHERWISE : CALL Beep
ENDCASE
</statement2></statement1></value2></value1></statement2></statement1></statement2></statement1></statement2>

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18
Q

FOR loops

A

FOR <identifier> ← <value1> TO <value2>
<statement(s)>
NEXT <identifier></identifier></value2></value1></identifier>

FOR <identifier> ← <value1> TO <value2> STEP <increment>
<statement(s)>
NEXT <identifier></identifier></increment></value2></value1></identifier>

Total ← 0
FOR Row ← 1 TO MaxRow
RowTotal ← 0
FOR Column ← 1 TO 10
RowTotal ← RowTotal + Amount[Row, Column]
NEXT Column
OUTPUT “Total for Row “, Row, “ is “, RowTotal
Total ← Total + RowTotal
NEXT Row
OUTPUT “The grand total is “, Total

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19
Q

REPEAT loops

A

REPEAT
<statement(s)>
UNTIL <condition></condition>

REPEAT
OUTPUT “Please enter the password”
INPUT Password
UNTIL Password = “Secret”

20
Q

WHILE loops

A

WHILE <condition>
<statement(s)>
ENDWHILE</condition>

WHILE Number > 9
Number ← Number – 9
ENDWHILE

21
Q

Defining and calling procedures

A

PROCEDURE <identifier>(<param1> : <data>, <param2> : <data>...)
<statement(s)>
ENDPROCEDURE</data></param2></data></param1></identifier>

CALL <identifier>(value1, value2, ...)</identifier>

22
Q

Defining and calling functions

A

FUNCTION <identifier>() RETURNS <data>
<statement(s)>
ENDFUNCTION</data></identifier>

FUNCTION <identifier>(<param1> : <data>,</data></param1></identifier>

<param2> : <data>...) RETURNS <data>
<statement(s)>
ENDFUNCTION

FUNCTION Max(Number1 : INTEGER, Number2 : INTEGER) RETURNS INTEGER
IF Number1 > Number2 THEN
RETURN Number1
ELSE
RETURN Number2
ENDIF
ENDFUNCTION
OUTPUT "Penalty Fine = ", Max(10, Distance*2)
</data></data></param2>

23
Q

By value or by reference

A

If there are several parameters passed by the same method,
the BYVAL or BYREF keyword need not be repeated.
Example – passing parameters by reference
PROCEDURE SWAP(BYREF X : INTEGER, Y : INTEGER)
Temp ← X
X ← Y
Y ← Temp
ENDPROCEDURE

24
Q

Handling text files

A

OPENFILE <file> FOR <file>
The file identifier may be a literal string containing the file names, or a variable of type STRING that has been
assigned the file name.
The following file modes are used:
* READ for data to be read from the file
* WRITE for data to be written to the file. A new file will be created and any existing data in the file will
be lost.
* APPEND for data to be added to the file, after any existing data.</file></file>

A file should be opened in only one mode at a time.
Data is read from the file (after the file has been opened in READ mode) using the READFILE command as
follows:
READFILE <file>, <variable>
The variable should be of data type STRING. When the command is executed, the next line of text in the file
is read and assigned to the variable.
The function EOF is used to test whether there are any more lines to be read from a given file. It is called as
follows:
EOF(<file>)
This function returns TRUE if there are no more lines to read (or if an empty file has been opened in READ
mode) and FALSE otherwise.
Data is written into the file (after the file has been opened in WRITE or APPEND mode) using the WRITEFILE
command as follows:
WRITEFILE <file>, <data>
Files should be closed when they are no longer needed using the CLOSEFILE command as follows:
CLOSEFILE <file></file></data></file></file></variable></file>

25
Q

Handling random files

A

Random files are opened using the RANDOM file mode as follows:
OPENFILE <file> FOR RANDOM
As with text files, the file identifier will normally be the name of the file.
The SEEK command moves the file pointer to a given location:
SEEK <file>, <address>
The address should be an expression that evaluates to an integer which indicates the location of a record to be
read or written. This is usually the number of records from the beginning of the file. It is good practice to explain
how the addresses are computed.
The command GETRECORD should be used to read the record at the file pointer:
GETRECORD <file>, <variable>
When this command is executed, the record that is read is assigned to the variable which must be of the
appropriate data type for that record (usually a user-defined type).
The command PUTRECORD is used to write a record into the file at the file pointer:
PUTRECORD <file>, <variable>
When this command is executed, the data in the variable is inserted into the record at the file pointer. Any data
that was previously at this location will be replaced.</variable></file></variable></file></file></file>

DECLARE Pupil : Student
DECLARE NewPupil : Student
DECLARE Position : INTEGER
NewPupil.LastName ← “Johnson”
NewPupil.Firstname ← “Leroy”
NewPupil.DateOfBirth ← 02/01/2005
NewPupil.YearGroup ← 6
NewPupil.FormGroup ← ꞌAꞌ
OPENFILE “StudentFile.Dat” FOR RANDOM
FOR Position ← 20 TO 10 STEP -1
SEEK “StudentFile.Dat”, Position
GETRECORD “StudentFile.Dat”, Pupil
SEEK “StudentFile.Dat”, Position + 1
PUTRECORD “StudentFile.Dat”, Pupil
NEXT Position
SEEK “StudentFile.Dat”, 10
PUTRECORD “StudentFile.Dat”, NewPupil
CLOSEFILE “StudentFile.dat”

26
Q

Methods and properties

A

PRIVATE Attempts : INTEGER
Attempts ← 3
PUBLIC PROCEDURE SetAttempts(Number : INTEGER)
Attempts ← Number
ENDPROCEDURE
PRIVATE FUNCTION GetAttempts() RETURNS INTEGER
RETURN Attempts
ENDFUNCTION
Methods will be called using object methods, for example:
Player.SetAttempts(5)
OUTPUT Player.GetAttempts()

27
Q

Constructors and inheritance

A

Constructors will be procedures with the name NEW.
CLASS Pet
PRIVATE Name : STRING
PUBLIC PROCEDURE NEW(GivenName : STRING)
Name ← GivenName
ENDPROCEDURE
ENDCLASS
Inheritance is denoted by the INHERITS keyword; superclass/parent class methods will be called using the
keyword SUPER, for example:
CLASS Cat INHERITS Pet
PRIVATE Breed: INTEGER
PUBLIC PROCEDURE NEW(GivenName : STRING, GivenBreed : STRING)
SUPER.NEW(GivenName)
Breed ← GivenBreed
ENDPROCEDURE
ENDCLASS

To create an object, the following format is used:

<object> ← NEW <class>(<param1>, <param2> ...)
For example:
MyCat ← NEW Cat("Kitty", "Shorthaired")
</param2></param1></class></object>

28
Q

What is a database?

A
  • A structured collection of data that can be accessed, managed, and updated.
  • Used to store information systematically for easy retrieval.
29
Q

What is a Database Management System (DBMS)?

A
  • Software that interacts with the database to manage data and operations.
  • Examples: MySQL, PostgreSQL, Oracle Database.
30
Q

What are the advantages of using a DBMS?

A
  • Efficient data management and retrieval.
  • Data integrity and security.
  • Supports concurrent access and data sharing.
31
Q

What is a relational database?

A
  • A database structured to recognize relations among stored items of information.
  • Data is organized into tables (relations) with rows and columns.
32
Q

What are the key components of a relational database?

A
  • Tables: Store data in rows and columns.
  • Fields (columns): Represent attributes of the data.
  • Records (rows): Represent individual entries in a table.
33
Q

What is a primary key in a relational database?

A
  • A unique identifier for each record in a table.
  • Ensures that no two records have the same primary key value.
34
Q

What is a foreign key in a relational database?

A
  • A field in one table that references the primary key in another table.
  • Used to establish a relationship between two tables.
35
Q

What is SQL (Structured Query Language)?

A
  • A language used to communicate with and manipulate databases.
  • Used for querying, updating, and managing relational databases.
36
Q

What are common SQL commands?

A
  • SELECT: Retrieves data from a database.
  • INSERT: Adds new data to a table.
  • UPDATE: Modifies existing data in a table.
  • DELETE: Removes data from a table.
37
Q

What is normalization in databases?

A
  • The process of organizing data to reduce redundancy and improve data integrity.
  • Involves dividing large tables into smaller, related tables.
38
Q

What are the different normal forms in database normalization?

A
  • 1NF (First Normal Form): Eliminates duplicate columns and ensures that each column contains atomic values.
  • 2NF (Second Normal Form): Ensures that all non-key attributes are fully functionally dependent on the primary key.
  • 3NF (Third Normal Form): Removes transitive dependencies.
39
Q

What is a transaction in the context of databases?

A
  • A sequence of one or more SQL operations that are treated as a single unit of work.
  • Ensures data integrity by adhering to ACID properties.
40
Q

What are the ACID properties of a transaction?

A
  • Atomicity: Transactions are all-or-nothing.
  • Consistency: Ensures data remains consistent before and after a transaction.
  • Isolation: Transactions are executed in isolation from one another.
  • Durability: Once a transaction is committed, it remains so, even in the event of a system failure.
41
Q

What is a database schema?

A
  • A blueprint that defines the structure of a database.
  • Includes tables, fields, relationships, indexes, and other elements.
42
Q

What is a data warehouse?

A
  • A centralized repository for storing large amounts of structured data.
  • Used for analysis and reporting purposes.
43
Q

What are the differences between OLTP and OLAP?

A
  • OLTP (Online Transaction Processing): Focuses on managing transaction-oriented applications.
  • OLAP (Online Analytical Processing): Focuses on analyzing data for decision-making.
44
Q

What is a NoSQL database?

A
  • A non-relational database that allows for flexible data models.
  • Examples: MongoDB, Cassandra, Redis.
45
Q

What are the advantages of NoSQL databases?

A
  • Handles large volumes of unstructured data.
  • Provides scalability and flexibility.
  • Suitable for distributed architectures.
46
Q

What is data redundancy

A

and why is it a concern in databases?

47
Q

What is a database index?

A
  • A data structure that improves the speed of data retrieval operations on a database table.
  • Helps to quickly locate and access the data.

Computer Science (16 decks)

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