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11 Programming
11.1 Programming basics
Key terms
Constant – a named value that cannot
change during the execution of a program.
Variable – a named value that can change
during the execution of a program.
Function – a set of statements that can
be grouped together and easily called
in a program whenever required, rather
than repeating all of the statements
each time. Unlike a procedure, a function
always returns a value.
Library routine – a tested and ready-to-
use routine available in the development
system of a programming language that
can be incorporated into a program.
Procedure – a set of statements that can
be grouped together and easily called
in a program whenever required, rather
than repeating all of the statements
each time.
11 Programming
In this chapter, you will learn about
★ declaring and assigning values to variables and constants
★ using programming constructs, including iteration with IF and CASE
structures
★ using programming constructs, including selection with three
different types of loop: count controlled, post-condition and
pre-condition
★ writing structured programs defining and using procedures and
functions.
WHAT YOU SHOULD ALREADY KNOW
Try this activity before you read the first part of
this chapter.
Write an algorithm, using pseudocode, to sort a list
of ten numbers. The numbers are to be input with
appropriate prompts, stored in an array, sorted in
ascending order and then searched for the number
27. The sorted list is to be output, as well as a
message stating whether 27 was found or not.
Write and test your algorithm using your chosen
programming language. Ensure that you test
your program with test data that includes 27 and
test data without 27.
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In order to write a program that performs a specific task or solves a given
problem, the solution to the task or problem needs to be designed and then
coded. This chapter demonstrates the programming tools used when coding a
solution, including basic statements, constructs and structures.
11.1.1 Constants and variables
A constant is a named value that cannot change during the execution of a
program. A variable is a named value that can change during the execution of
a program. All variables and constants should be declared before use. Constants
will always be assigned a value when declared. It is good practice to assign a
value to any variables that are used, so that the programmer is certain of the
starting value.
It is good practice to create an identifier list and check that every variable on
that list has been declared and a value assigned before any data manipulation
is programmed.
Note that some programming languages (for example, Python) do not support
the declaration of variables and the concept of a constant; in such cases, the
assignment of a value at the start of a program will ensure that a variable
of the correct data type can be used. An identifier that is to be used as a
constant can also be assigned a value. However, it is important that the
programming concepts of data declaration and the difference between
variables and constants are clearly understood and can be demonstrated using
pseudocode.
Write an algorithm using pseudocode to calculate and output the volume and
surface area of a sphere for any radius that is input.
Example 11.1
Solution
First create an identifier table.
Identifier name Description
radius
Stores radius input
volume
Stores result of volume calculation
surfaceArea
Stores result of surface area calculation
pi
Constant set to 3.142
Then declare constants and variables in pseudocode.
DECLARE radius : REAL
DECLARE volume : REAL
DECLARE surfaceArea : REAL
CONSTANT pi ← 3.142
Provide pseudocode for input, process and output.
Input usually includes some output in the form of prompts stating what should be
input.
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Table 11.1 shows the declaration of some of the constants and variables from
Example 11.1 in the three prescribed programming languages.
While the Cambridge International AS Level syllabus does not require you
to be able to write program code, the ability to do so will increase your
understanding, and will be particularly beneficial if you are studying the full
Cambridge International A Level course.
OUTPUT "Please enter the radius of the sphere "
INPUT radius
Check the value of the radius, to ensure that it is suitable.
WHILE radius <= 0 DO
OUTPUT "Please enter a positive number "
INPUT radius
ENDWHILE
Calculate the volume and the surface area; this is the processing part of the
algorithm.
volume ← (4 / 3) * pi * radius * radius * radius
surfaceArea ← 4 * pi * radius * radius
Finally, the results of the calculations need to be output.
OUTPUT "Volume is ", volume
OUTPUT "Surface area is ", surfaceArea
Declarations of constants and variables Language
pi = 3.142
Python does not require any separate
declarations and makes no difference
between constants and variables
Dim radius As Decimal
Dim volume As Decimal
Dim surfaceArea As Decimal
Const pi As Decimal = 3.142
Or
Dim radius, volume, surfaceArea As Decimal
Public Const pi As Decimal = 3.142
In VB, constants and variables are
declared before use. Declarations
can be single statements or can
contain multiple declarations in a
single statement. Constants can
be explicitly typed as shown or
implicitly typed, for example:
Const pi = 3.142
final double PI = 3.142;
:
:
double volume = (4 / 3) * PI * radius * radius * radius;
In Java, constant values are declared
as variables with a final value so no
changes can be made. These final
variable names are usually capitalised
to show they cannot be changed.
Variables are often declared as they
are used rather than at the start of
the code
▲ Table 11.1
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11.1 Programming basics
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Table 11.3 below shows how to check the value of the radius in each of the
three programming languages.
Check that the value of the radius is a
positive number
Language
while radius <= 0:
Python uses a check at the start of
the loop
Do
:
Loop Until radius > 0
VB uses a check at the end of the
loop
do
{
:
}
while (radius <= 0);
Java uses a check at the end of the
loop
▲ Table 11.3
Table 11.4 below shows how to calculate the volume and the surface area in
each of the three programming languages.
Table 11.2 below gives examples of the input statements in the three
prescribed programming languages.
Calculate the volume and the surface area Language
volume = (4 / 3) * pi * radius * radius * radius
surfaceArea = 4 * pi * radius * radius
Python
volume = (4 / 3) * pi * radius * radius * radius
surfaceArea = 4 * pi * radius * radius
VB
double volume = (4 / 3) * PI * radius * radius * radius;
double surfaceArea = 4 * PI * radius * radius;
Java (variables declared as used)
▲ Table 11.4
Input statements Language
radius = float(input("Please enter the radius of the sphere "))
Python combines the prompt
with the input statement and
the type of the input
Console.Write("Please enter the radius of the sphere ")
radius = Decimal.Parse(Console.ReadLine())
VB uses a separate prompt
and input. The input specifies
the type
import java.util.Scanner;
:
Scanner myObj = new Scanner(System.in);
:
System.out.println("Please enter the radius of the sphere ");
double radius = myObj.nextDouble();
In Java, the input library has
to be imported at the start of
the program and an input object
is set up. Java uses a separate
prompt and input. The input
specifies the type and declares
the variable of the same type
▲ Table 11.2
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The complete programs are shown below:
Python
pi = 3.142
radius = float(input("Please enter the radius of the sphere "))
while radius <= 0:
radius = float(input("Please enter the radius of the sphere "))
volume = (4 / 3) * pi * radius * radius * radius
surfaceArea = 4 * pi * radius * radius
print("Volume is ", volume)
print("Surface area is ", surfaceArea)
VB
Module Module1
Public Sub Main()
Dim radius As Decimal
Dim volume As Decimal
Dim surfaceArea As Decimal
Const pi As Decimal = 3.142
Do
Console.Write("Please enter the radius of the sphere ")
radius = Decimal.Parse(Console.ReadLine())
Loop Until radius > 0
volume = (4 / 3) * pi * radius * radius * radius
surfaceArea = 4 * pi * radius * radius
Console.WriteLine("Volume is " & volume)
Console.WriteLine ("Surface area is " & surfaceArea)
Console.ReadKey()
End Sub
End Module
Table 11.5 below shows how to output the results in each of the three
programming languages.
Output the results Language
print("Volume is ", volume)
print("Surface area is ", surfaceArea)
Python uses a comma
Console.WriteLine("Volume is " & volume)
Console.WriteLine ("Surface area is " & surfaceArea)
VB uses &
System.out.println("Volume is " + volume);
System.out.println("Surface area is " + surfaceArea);
Java uses +
▲ Table 11.5
Every console program
in VB must contain a
main module. These
statements are shown
in red
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11.1 Programming basics
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Java
import java.util.Scanner;
class Activity11A
{
public static void main(String args[])
{
Scanner myObj = new Scanner(System.in);
final double PI = 3.142;
dou ble radius;
do
{
System.out.println("Please enter the radius of the sphere ");
radius = myObj.nextDouble();
}
while (radius <= 0);
double volume = (4 / 3) * PI * radius * radius * radius;
double surfaceArea = 3 * PI * radius * radius;
System.out.println("Volume is " + volume);
System.out.println("Surface area is " + surfaceArea);
}
}
Many programming languages contain built-in functions ready to be used.
For example, DIV returns the integer part of a division and MOD returns the
remainder. For example, DIV(10,3) will return 3, and MOD(10,3) will return 1.
See Section 11.3.2 for guidance on how to define a function.
Functions are used for string manipulation. Strings are one of the best ways
of storing data. The comparison of data stored in a string has many uses, for
example, checking passwords, usernames and other memorable data.
ACTIVITY 11A
Write and test the algorithm in your chosen programming language. Extend
the algorithm to allow for more than one calculation, ending when –1 is
input, and test it with this test data: 4.7, 34, –11, 0 and –1.
Every console program
in Java must contain a
class with the file name
and a main procedure.
These statements are
shown in red
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Write an algorithm using pseudocode to check that the length of a password and the
first and last letter of a password input is correct.
You can use these string manipulation functions:
LENGTH(anyString : STRING) RETURNS INTEGER returns the integer value
representing the length of anyString.
RIGHT(anyString: STRING, x : INTEGER) RETURNS STRING returns
rightmost x characters from anyString.
LEFT(anyString: STRING, x : INTEGER) RETURNS STRING returns
leftmost x characters from anyString.
MID(anyString: STRING, x : INTEGER, y : INTEGER) RETURNS
STRING returns y characters starting at position x from anyString.
Example 11.2
Solution
First create an identifier table.
Identifier name Description
storedPassword
Stores password
inputPassword
Stores password to be checked
size
Stores length of password to be checked
CONSTANT storedPassword ← "Secret"
DECLARE inputPassword : STRING
DECLARE size : INTEGER
OUTPUT "Please enter your password "
INPUT inputPassword
size ← LENGTH(inputPassword)
IF size = LENGTH(storedPassword)
THEN
IF (LEFT(inputPassword, 1) = LEFT(storedPassword, 1)) AND
(RIGHT(inputPassword, 1) = RIGHT(storedPassword, 1))
THEN
OUTPUT "Password entered has correct first and last letters"
ELSE
OUTPUT "Password entered is incorrect"
ENDIF
ELSE
OUTPUT "Password entered is incorrect"
ENDIF
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Table 11.6 below shows the string manipulation functions for Example 11.2 in
the three prescribed programming languages.
String manipulation functions Language
le n(inp utPassw ord)
inputPassword[0]
i n p u tP a s s w o r d[-1:]
Python
first character of string
last character of string
Len(inputPassw or d)
Left(inputPassword, 1)
R ig ht(i np utP a ss wor d, 1)
VB
first character of string
last character of string
int size =inputPassword.length();
inputPassword.charAt(0)
inputPassword.charAt(size - 1)
Java
first character of string
last character of string
▲ Table 11.6
11.1.2 Library routines
Many programming language development systems include library routines
that are ready to incorporate into a program. These routines are fully tested
and ready for use. A programming language IDE usually includes a standard
library of functions and procedures as well as an interpreter and/or a compiler.
These standard library routines perform tasks such as input/output that are
required by most programs.
ACTIVITY 11C
Find out about the standard libraries that are included with the
programming language you use. Identify at least six routines included in the
library.
11.2 Programming constructs
11.2.1 CASE and IF
The algorithm in Example 11.2 uses a nested IF statement, as there are two
different choices to be made. Where there are several different choices to be
made, a CASE statement should be used for clarity.
Figure 11.1 shows that choices can be made using a condition based on
» the value of the identifier being considered, for example < 10
» a range of values that the identifier can take, for example 1:10
» the exact value that the identifier can take, for example 10.
And a final catch all for an identifier that met none of the conditions given
OTHERWISE.
ACTIVITY 11B
Write the algorithm in
Example 11.2 in your
chosen programming
language and
test it with this
test data: "Sad",
"Cheese", "Secret"
and "secret". Find
out how you could
extend your program
to match upper or
lower-case letters.
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For each criterion there can be one or many statements to execute.
CASE OF
<Identifier>
OTHERWISE
Statement 5
Statement 1
Statement 2
Statement 3
Statement 4
Value
Range
Condition
▲ Figure 11.1
For example, choices from a menu can be managed by the use of a CASE statement.
Menu
1 Routine 1
2 Routine 2
3 Routine 3
4 Routine not
written
5 Routine not
written
6 Routine not
written
10 Exit
DECLARE choice : INTEGER
OUTPUT "Please enter your choice "
INPUT choice
CASE choice OF
1 : OUTPUT "Routine 1 "
2 : OUTPUT "Routine 2 "
3 : OUTPUT "Routine 3 "
4 … 6 : OUTPUT "Routine not written"
10 : Exit
OTHERWISE OUTPUT "Incorrect choice"
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11
Table 11.7 below shows the case statements in VB and Java. Python does not
use this construct.
Case statements for menu choices Case statements
for menu choices
Select choice
Case 1
Console.Writeline ("Routine 1")
Case 2
Console.Writeline ("Routine 2")
Case 1
Console.Writeline ("Routine 3")
Case 4, 5, 6
Console.Writeline ("Routine not written")
Case 10
Console.Writeline ("Exit")
Case Else
Console.Writeline ("Incorrect choice")
End Select
VB uses Else
instead of
OTHERWISE
switch (choice)
{
case 1:
System.out.println("Routine 1");
break;
ca se 2:
System.out.println("Routine 2");
break;
case 3:
System.out.println("Routine 3");
break;
ca se 4:
case 5:
cas e 6:
System.out.println("Routine not written");
break;
Java uses default
instead of
OTHERWISE and
uses break to pass
control to the end
of the code block
when a section is
finished
case 10:
System.out.println("Exit");
break;
default:
System.out.println("Incorrect choice");
}
▲ Table 11.7
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ACTIVITY 11D
1 Write an algorithm using pseudocode to either add, subtract, multiply
or divide two numbers and output the answer. The two numbers are
to be input with appropriate prompts followed by +, −, * or /. Any other
character is to be rejected.
2 Check that your pseudocode algorithm works by writing a short program
in your chosen programming language from your pseudocode statements
using the same names for your identifiers.
11.2.2 Loops
Loops enable sections of code to be repeated as required. They can be
constructed in different ways to meet the requirements of an algorithm.
1 a count-controlled loop FOR … NEXT
2 a post-condition loop REPEAT … UNTIL
3 a pre-condition loop WHILE … DO … ENDWHILE
In order to program efficiently, it is important to select the appropriate loop
structure to efficiently solve the problem. For example, it is better to use a
REPEAT … UNTIL loop rather than a WHILE … DO … ENDWHILE loop for
a validation check. The statements inside the loop must always be executed at
least once and there is no need for a second input statement.
For example, to check that a value is between 0 and 10 inclusive.
REPEAT … UNTIL
REPEAT
OUTPUT "Enter value "
INPUT value
UNTIL value < 0 OR value > 10
WHILE … DO … ENDWHILE
OUTPUT "Enter value "
INPUT value
WHILE value < 0 OR value > 10 DO
OUTPUT "Enter value "
INPUT value
ENDWHILE
Table 11.8 below shows post-condition loops in VB and Java. Python only uses
pre-condition loops.
Post condition loops Language
Do
<statements>
Loop Until <condition>
VB
Do
{
<statem e nts>;
}
while (<condition>);
Java
▲ Table 11.8
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11.3 Structured programming
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Table 11.9 below shows pre-condition loops in each of the three programming
languages.
Pre-condition loops Language
while <condition>:
<statements>
Python
While <condition>
<statements>
End While
VB
while (<condition>)
{
<statem e nts>;
}
Java
▲ Table 11.9
Where the number of repetitions is known, a FOR … NEXT loop is the best
choice, as the loop counter does not have to be managed by the programmer.
11.3 Structured programming
Key terms
Parameter – a variable applied to a procedure or
function that allows one to pass in a value for the
procedure to use.
By value – a method of passing a parameter to a
procedure in which the value of the variable cannot be
changed by the procedure.
By reference – a method of passing a parameter to
a procedure in which the value of the variable can be
changed by the procedure.
Header (procedure or function) – the first statement in
the definition of a procedure or function, which contains
its name, any parameters passed to it, and, for a
function, the type of the return value.
Argument – the value passed to a procedure or function.
11.3.1 Procedures
When writing an algorithm, there are often similar tasks to perform that make
use of the same groups of statements. Instead of repeating these statements
every time they are required, many programming languages make use of
subroutines or named procedures. A procedure is defined once and can be
called many times within a program.
Different terminology is used by some programming languages. Procedures are
» void functions in Python
» subroutines in VB
» methods in Java.
To be consistent, we will use the term procedure – you will need to check what
to do in your chosen programming language.
A procedure can be defined in pseudocode, as follows:
PROCEDURE <identifier>
<statements>
ENDPROCEDURE
ACTIVITY 11E
Write and test a
short program
in your chosen
programming
language to check
that an input value
is between 0 and 10
inclusive.
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The procedure can then be called many times:
CALL <identifier>
For example, a procedure to print a line of stars would be defined as follows:
PROCEDURE stars (Number : INTEGER)
FOR Counter 1 TO Number
OUTPUT"*"
NEXT Counter
ENDPROCEDURE
And used like this:
CALL stars
ACTIVITY 11F
Using the procedure
definition and
call given for
your chosen
programming
language, write a
short program to
define and call a
procedure to write a
line of stars.
Table 11.10 below shows how to define this procedure in each of the three
prescribed programming languages.
Procedure – definition Language
d e f s t a r s():
print("************")
Python
Su b sta r s()
Console.WriteLine("************")
End Sub
VB
static void stars()
{
System.out.println("***********");
}
Java
▲ Table 11.10
Table 11.11 shows how it can be used.
Procedure – call Language
sta rs()
Python
sta rs()
VB
s t a r s();
Java
▲ Table 11.11
It is often useful to pass a value to a procedure that can be used to modify the
action(s) taken. For example, to decide how many stars would be output. This is
done by passing a parameter when the procedure is called.
A procedure with parameters can be defined in pseudocode, as follows:
PROCEDURE <identifier>(<parameter1>:<datatype>, <parameter2>:<datatype>...)
<statements>
ENDPROCEDURE
The procedure can then be called many times:
CALL <identifier> (Value1, Value2...)
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11.3 Structured programming
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ACTIVITY 11G
Extend your short program in your chosen programming language to define
and use a procedure that accepts a parameter to write a line with a given
number of stars.
There are two methods of passing a parameter to a procedure: by value and by
reference. When a parameter is passed by value, if a variable is used, the value
of that variable cannot be changed within the procedure. When a parameter is
passed by reference the value of the variable passed as the parameter can be
changed by the procedure.
The procedure to print a line with a given number stars would be defined as
follows:
PROCEDURE stars (Number : INTEGER)
OUTPUT "************" ENDPROCEDURE
And used like this, to print seven stars:
CALL stars (7)
or
myNumber ← 7
CALL stars (myNumber)
The interface between a procedure and a program must match the procedure
definition. When a procedure is defined with parameters, the parameters in the
procedure call must match those in the procedure definition.
Table 11.12 below shows how to define a procedure with a parameter in each of
the three programming languages.
Procedure with parameter – definition Language
def stars(number):
for counter in range (number):
print("*", end = '')
Python
Note: end = ' ' ensures that the stars
are printed on one line without spaces
between them
Sub stars(number As Integer)
Dim counter As Integer
For counter = 1 To number
Co n sole.Write("*")
Next
End Sub
VB
static void stars(int number)
{
for (int counter = 1; counter <= number; counter ++)
{
System.out.print("*");
}
}
Java
▲ Table 11.12
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A procedure with parameters passed by reference can be defined in pseudocode
as follows:
For example, a procedure to convert a temperature from Fahrenheit to Celsius
could be defined as follows:
PROCEDURE celsius(BYREF temperature : REAL)
temperature
← (temperature – 32) / 1.8
ENDPROCEDURE
And used as follows:
C A L L celsius(m y Te m p)
Table 11.13 below shows how to pass parameters in the three programming
languages.
Passing parameters Language
Def celsius(temperature):
Python
all data is passed by value
Sub celsius(temperature As Decimal)
Sub celsius(ByVal temperature As Decimal)
Sub celsius(ByRef temperature As Decimal)
VB
parameter passed implicitly
by value
parameter passed by value
parameter passed by
reference
static void celsius(double temperature)
Java
all data is passed by value
▲ Table 11.13
ACTIVITY 11H
Write an algorithm in pseudocode to use a procedure, with a parameter
passed by reference, to convert a temperature from Celsius to Fahrenheit.
11.3.2 Functions
When writing an algorithm, there are often similar calculations or tasks to
perform that make use of the same groups of statements and always produce
an answer. Instead of repeating these statements every time they are required,
many programming languages make use of subroutines or named functions. A
function always returns a value; it is defined once and can be called many times
within a program. Functions can be used on the right-hand side of an expression.
Different terminology is used by some programming languages. Functions are
» fruitful functions in Python
» functions in VB
» methods with returns in Java.
PROCEDURE <identifier> (BYREF <parameter1>:<datatype>, <parameter2>:<datatype>...)
<statements>
ENDPROCEDURE
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11.3 Structured programming
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A function without parameters is defined in pseudocode as follows:
FUNCTION <identifier> RETURNS <data type>
<statements>
ENDFU NCTION
A function with parameters is defined in pseudocode as follows:
The keyword RETURN is used as one of the statements in a function to specify
the value to be returned. This is usually the last statement in the function
definition. There can be more than one RETURN used in a function if there are
different paths through its statements. This technique needs to be used with
great care. For example, a function to find a substring of a given length starting
at a given place in a string that returns a null string rather than an error could be:
Functions are used as part of an expression. The value returned by the function
is used in the expression.
For example, the procedure used previously to convert a temperature from
Fahrenheit to Celsius could be written as a function:
FUNCTION celsius (temperature : REAL) RETURNS REAL
RETURN (temperature – 32) / 1.8
ENDFUNCTION
And used as follows:
myTemp ← celsiu s(m y Te m p)
The interface between a function and a program must match the function
definition. When a function is defined with parameters, the parameters in the
function call must match those in the function definition.
FUNCTION <identifier>(<parameter1>:<datatype>, <parameter2>:<datatype>...)
RETURNS <data type>
<statements>
ENDFUNCTION
FUNCTION substring (myString : STRING, start : INTEGER, length : INTEGER)
RETURNS STRING
IF LENGTH (myString) >= length + start
THEN
RETURN MID (myString, start, length)
ELSE
RETU RN ""
ENDIF
ENDFUNCTION
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Table 11.14 below shows how to write this function in each of the three
programming languages.
Function example Language
def celsius(temperature):
return (temperature - 32) / 1.8
Python
Function celsius(ByVal temperature As Decimal) As Decimal
Return (temperature - 32) / 1.8
End Function
VB
static double celsius(double temperature)
{
return (temperature - 32) / 1.8;
}
Java
▲ Table 11.14
ACTIVITY 11I
Re-write the algorithm you wrote in Activity 11H as a function, with a parameter,
to convert a temperature from Celsius to Fahrenheit. Test your algorithm by
writing a short program in your chosen programming language to define and
use this function. Note the differences in your programs and state, with reasons,
which is the better structure to use for this algorithm: a procedure or a function.
When procedures and functions are defined, the first statement in the
definition is a header, which contains
» the name of the procedure or function
» any parameters passed to the procedure or function
» the type of the return value for a function.
When procedures or functions are called, the parameters or arguments (the
values passed to the procedure or function) must be in the same order as the
parameters in the declaration header and each argument must be of the same
type as the parameter given in the header. Procedure calls are single stand-alone
statements and function calls form part of an expression on the right-hand side.
1 Use pseudocode to declare these variables and constants.
You will need to decide which identifiers are variables and which are constants.
[6]
Identifier name Description
height
Stores value input for length of height
maxHeight
Maximum height, 25
width
Stores value input for length of width
maxWidth
Maximum width, 30
hypotenuse
Stores calculated value of hypotenuse
area
Stores calculated value of area
End of chapter
questions
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11.3 Structured programming
11
2 Write a pseudocode algorithm to input the height and width of a right-angled
triangle and check that these values are positive and less than the maximum
values given in question 1. [4]
3 a) For this question, you will need to use this function, which returns the real
value of the square root of anyPosVal:
SQUAREROOT(anyPosVal : REAL) RETURNS REAL
Extend your algorithm for Question 2 to
i) calculate the hypotenuse [2]
ii) calculate the area [2]
iii) calculate the perimeter. [2]
b) Provide a menu to choose which calculation to perform. [3]
c) Check that all the above work by writing and testing a program in your
chosen programming language. [6]
4 Explain what is meant by the term library routine.
Give two examples of uses of library routines. [4]
5 Procedures and functions are subroutines.
Explain what is meant by
a) a procedure [2]
b) a function [2]
c) a parameter [2]
d) a procedure or function header. [2]
6 Explain the difference between
a) a procedure and a function [2]
b) passing parameters by value and by reference [2]
c) defining a procedure and calling a procedure. [2]
7 A driver buys a new car.
The value of the car reduces each year by a percentage of its current value.
The percentage reduction is:
– in the first year, 40%
– in each following year, 20%
The driver writes a program to predict the value of the car in future years.
The program requirements are:
– enter the cost of the new car (to nearest $)
– calculate and output the value of the car at the end of each year
– the program will end when either the car is nine years old, or when the value
is less than $1000.
a) Study the incomplete pseudocode which follows in part b) and copy and
complete this identifier table. [3]
Identifier Data type Description
➔
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11 Programming
11
b) Copy and complete the pseudocode for this design. [6]
OUTPUT "Enter purchase price"
INPUT PurchasePrice
CurrentValue
← ...............................................
YearCount ← 1
W H I L E ......................... A N D .......................
I F ........................................................
THEN
CurrentValue ← CurrentValue * (1 – 40 / 100)
ELSE
CurrentValue ← ......................................
ENDIF
OUTPUT YearCount, CurrentValue
...............................................................
ENDWHILE
Cambridge International AS & A Level Computer Science 9608
Paper 21 Q5 November 2015
457591_11_CI_AS & A_Level_CS_264-282.indd 282 25/04/19 11:21 AM
