TABLE OF CONTENTS
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INTRODUCTION TO PROGRAMMING .................................................................. 1
SELECTION S TATEMENTS ................................................................................ 10
LOOP STATEMENTS ........................................................................................ 2 4
ARRAYS ......................................................................................................... 36
TRACING ....................................................................................................... 43
CODE ERRORS ............................................................................................... 64
DATABASES ................................................................................................... 7 5
DEFINITIONS ................................................................................................. 100
THEORY QUESTIONS .................................................................................... 109
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Introduction to programming
Definition of a program:
A list of instructions that does a specific task.
Example:
Write a program that reads two numbers from the user and print out their sum.
In other words, we need to write a program to solve the following equation:
Z=A+B
Solution:
To write the program we go through four phases:
1
Analysis
2
Design
3
Implementation
4
Testing
1.1 Analysis
In the analysis phase we try to figure out what are the inputs of the program, processing that it
should do and the outputs it shall produce.
Back to our program:
 Inputs: A, B
Processing: Z = A + B
 Output: Z
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Introduction to programming
Operators
Types of operators:
1
Arithmetic operators
2
Logic operators
3
Assignment operator
Arithmetic Operators
The following table shows the various Arithmetic operators and what they do:
Arithmetic operators
Operator
Symbol
Description
Multiplication
*
Division
/
Divides the left operand by the right operand
Example: x/y
Subtraction
-
Subtracts the right operand from the left operand
Example: x - y
Addition
+
Adds the left operand to the right operand
Example: x + y
Power
^
Raises the left operand to the power of the right operand
Example: ! ! is written as x ^ y
Multiplies the left operand by the right operand.
Example: x * y
Logic Operators
The following table shows some Logic operators:
Comparison Operators
Operator
Symbol
Greater than
>
Less than
<
Equal
=
Greater than or equal to
>=
Less than or equal to
<=
Not equal to
<>
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Introduction to programming
Assi gnment Operator
This operator assigns a value or an expression to a variable.
The symbol used for this operator is an arrow pointing left: 
Examples of assignment operator:
Cost ← 10
Price ← Cost * 2
Tax ← Price * 0.14
Service ← Price * 0.12
PaidAmount ← Tax + Service
1.2 Design
After the analysis phase is done, we design the Algorithm.
An algorithm is a step-by-step solution to a given problem.
We design algorithm using one of two methods:
 Flowcharts
 Pseudocode
1.2.1 Flowcharts
Definition:
Diagram that designs the steps of a program by using a standard set of symbols joined by
lines to show the direction of flow.
Flowcharts have some shapes that we use to draw the diagram with:
Shape
Name
Description
Start/End
An oval represents a start
or end point
Arrows
A line is a connector that
shows the relationship
between the shapes
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Introduction to programming
Input / Output
A parallelogram
represents output or input
Process
A rectangle is a process
Decision
A diamond indicates a
decision
Solving our problem using the flowchart design: Z = A + B
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Introduction to programming
1.2.2 Pseudocode
Definition:
Uses English words and mathematical notations to design the steps of a program.
INPUT Keywords
To allow the user to input a value we use one of two keywords:
INPUT
READ
OUTPUT Keywords
To show the user the value of a variable we use one two keywords:
OUTPUT
PRINT
Writing the program in pseudocode:
O U T P U T “ P l e a s e en t e r t w o n u m b e r s t o a d d ”
INPUT A
INPUT B
Z ← A + B
OUTPUT Z
1.3 Implementation
After designing the algorithm, the algorithm is transformed into code using a programming
language.
Examples of programming languages:
 C++
Java
 Python
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Introduction to programming
1.4 Testing
The last phase of the programming, this phase is done after implementation by testing how the
program works, we will discuss this later.
Variables
Definition:
A variable is a named memory location that stores a value that can change during the
execution of a program.
Rules for naming variables:
Variable names cannot contain spaces
Variable names cannot start with numbers
 Variable name should not be a keyword of pseudocode
Variable names should be meaningful to the value it stores
Examples of valid variable names:
number
total
  c o u n t
  c o u n t 1
count_students
countStudents
Examples of invalid variable names:
count
  1 c o u n t
OUTPUT
students
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Constants
Definition:
A constant is a named memory location that stores a value that does not change during the
execution of a program.
Note that:
Constants have the same naming rules as variables.
Data Types
Computers need to know the data type for every variable, to make the processing on this
variable as effective as possible.
The following table shows the data types used in programs:
Data type
Definition
Examples
Integer
A positive or negative whole number be used in
mathematical operations
150, -100, 0
Real
A positive or negative number that has a fractional
part that can be used in mathematical operations
100.5, -15.2
Char
A single character from the keyboard
H
String
A sequence of characters
Boolean
Data with two possible values
Hello World,
A312_@odq
TRUE/FALSE
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Introduction to programming
D eclaration
When declaring a variable you have to do two
Give your variable a valid name
Give it a data type
things:
Declaration syntax in pseudocode:
DECLARE [VARIABLE NAME] : [VARAIBLE DATA TYPE]
The complete pseudocode solution:
DECLARE Num1: REAL
DECLARE Num2: REAL
DECLARE Sum: REAL
O U T P U T “ P l e a s e ent er t w o n u m b e r s t o a d d ”
INPUT Num1
INPUT Num2
Sum Num1 + Num2
O U T P U T “The number is ”,Su m
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Introduction to programming
Sequential Exercise
1
Write a program to input length, width and depth of a pool. The program should
output the volume and price of pool.
The price of the pool is dependent on the volume: $1 per 100 cm 3 .
2
Write a program that inputs a mark and raw score. The program should output the
percentage
3
Write a program that converts a person’s height in inches to centimeters and their
weight in stones into kilograms [1 inch = 2.54 cm and 1 stone 6.364 kg]
4
Write a pseudocode that inputs days from the user. The program should output how
many weeks and days. A function INT( ) should be used.
The function takes a number and returns the whole number .
For example INT(1.5) = 1
5
Write a program that inputs diameter and depth of a round concrete slab in mm. The
price of one slab is $0.05 per 10000 mm 3 .
HINT: Volume of a cylinder = π*radius 2 *depth
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Part I
IF..THEN..ENDIF
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Conditional Statements
Definition of Sequential statements:
Statements are executed one after another according to their order.
Definition of Conditional/Selection statements:
Selective statement(s) are executed depending on meeting certain criteria.
Purpose of Conditional statements:
To allow different paths through a program depending on meeting certain criteria.
2.1 IF .. THEN .. ELSE .. ENDIF:
Definition:
A conditional structure with different outcomes for true and false.
Purpose:
It allows for checking complex conditions.
IF [CONDITION] THEN
// What to do if the condition is true
ELSE
// What to do if the condition is false
ENDIF
Example 2.1.1:
Design a program, using pseudo-code and flowchart, which takes a number as input and
outputs whether the number is zero or non-zero.
Pseudo-code Solution:
DECLARE num: REAL
OUTPUT “Enter a number”
INPUT num
IF num = 0 THEN
OUTPUT “The number is zero”
ELSE
OUTPUT “The number is non-zero”
ENDIF
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Conditional Statements
Flowchart Solution:
Example 2.1.2:
Design a program, using pseudo-code and flowchart, which takes a number as input and
outputs whether the number is positive or negative or zero.
Pseudo-code Solution:
DECLARE num: REAL
OUTPUT “Enter a number”
INPUT num
IF num > 0 THEN
OUTPUT “The number is positive”
ELSE
IF num < 0 THEN
OUTPUT “The number is negative”
ELSE
OUTPUT “The number is negative”
ENDIF
ENDIF
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Conditional Statements
Flowchart Solution:
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Conditional Statements
Validation
Often we need to check that the user has not entered unacceptable data, take the example of
dividing two numbers, you cannot divide by zero. So we have to anticipate mistakes users
might do, this is called Validation.
Example:
Read two numbers and divide them Z = A / B.
Pseudo-code Solution:
DECLARE Num1,Num2,Result: REAL
INPUT Num1,Num2
IF Num2 = 0 THEN
OUTPUT “MATH ERROR”
ELSE
Result   Num1 / Num2
OUTPUT Result
ENDIF
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Conditional Exercise 1
1
Design a program, using pseudocode and flowchart, which inputs from the user length
of a square. The program calculates the perimeter of the square.
AN ERROR MESSAGE SHOULD BE DISPLAYED WHEN NEEDED.
2
Design a program using pseudocode which inputs a number from the user and outputs
the square root. Use a function called Sqrt, which takes a number and returns the
square root of the number
DONOT FORGET TO VALIDATE THE NUMBER.
3
Design a program, using pseudocode and flowchart, which takes a number between 1
and 7 and outputs the day name (Day 1= Sunday).
A n error message should be displayed if the user enters invalid day number
4
Design a program, using pseudocode and flowchart, that takes two numbers and the
operation as input and performs a basic operation (+, - or *) as per user requires.
A n error message should be displayed if the user enters invalid operation
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Part II
IF..THEN..ENDIF
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Conditional Statements
Example 2.1.3:
Design a program, using pseudo-code and flowchart, which takes a number and prints
“In range” if the number is between 1 and 10 inclusive, otherwise the program outputs
“Outside range”.
Pseudo-code Solution:
DECLARE Num: REAL
O U T P U T “Enter a number”
INPUT Num
IF Num >= 50 AND Num <= 100 THEN
O U T P U T “In range”
ELSE
O U T P U T “Outside range”
ENDIF
Flowchart Solution:
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Conditional Statements
Example 2.1.4:
Design a program, using pseudocode and flowchart, which takes marks in an exam as input
and outputs the grade according to the following grade boundaries:
Mark
Grade
90 - 100
A
80 – 89
B
70 – 79
C
< 70
F
Pseudo-code Solution:
DECLARE Mark: INTEGER
O U T P U T “Enter the mar k”
INPUT Mark
IF Mark >= 90 AND Mark <= 100 THEN
OUTPUT “A”
ELSE
IF Mark >= 80 AND Mark <= 89 THEN
OUTPUT “B”
ELSE
IF Mark >= 70 AND Mark <= 79 THEN
OUTPUT “C”
ELSE
IF Mark >= 0 AND Mark <= 69 THEN
OUTPUT “F”
ELSE
O U T P U T “Invalid m a rk”
ENDIF
ENDIF
ENDIF
ENDIF
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Conditional Statements
Flowchart Solution:
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Conditional Statements
Conditional Exercise 2
1
Write a pseudocode that reads a number and prints “Correct range” in case the
number is between 30 and 50 exclusive. Otherwise the program outputs “Wrong
range”.
2
Extend the above pseudocode so that if the number is in wrong range, a message will
be displayed saying whether the number is above range or below range.
3
Design a program, using pseudocode and flowchart, which takes three numbers from
the user and outputs the minimum.
4
Design a program, using pseudocode and flowchart, that takes the salary of 3 months
(salaries cannot be negative) as inputs and output the financial status according to the
following table:
Average salary of 3 months
Financial Status
>10,000
Rich
2,000 – 10,000
Moderate
<2,000
Poor
DO NOT VALIDATE THE SALARIES.
5
Design a program, using pseudocode and flowchart, that:
 T akes from the user the number of hours worked this week and their hourly
rate of pay.
 The program should calculate and output the gross pay.
 If the number of hours worked is more than 40, then the extra hours are paid 1.5
times the rate.
The program should stop and display an error message if the number of hours worked is not in
the range of 0 to 60 OR if the user entered a negative hourly rate of pay.
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Part III
CASE..OTHERWISE..ENDCASE
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Conditional Statements
2.2 CASE .. OF .. OTHERWISE .. ENDCASE:
Definition:
A conditional structure that allows selection to be made based on value of a variable.
Purpose:
Used to test for a large number of discrete values.
CASE [ANY VARIABLE] OF
1: // do something if the variable equals 1
2: // do something if the variable equals 2
OTHERWISE:
// do something if the variable doesn’t equal any of the cases.
ENDCASE
Example 2.2.1:
Design a program, using pseudocode and flowchart, which takes a course number as input and
outputs the corresponding course name according to this table:
Course Number
Course Name
1
Computer Science
2
ICT
3
Math
4
Biology
Pseudocode Solution:
DECLARE CourseNo: INTEGER
OUTPUT “Enter the course number“
INPUT CourseNo
CASE CourseNo OF
1: OUTPUT “Compute
2: OUTPUT “ICT”
Science”
3: OUTPUT “Math”
4: OUTPUT “Biology”
OTHERWISE
OUTPUT “Invalid Course number”
ENDCASE
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Conditional Statements
Flowchart Solution:
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Conditional Statements
E x a m p l e 2 .2.2:
Write pseudocode that takes two numbers as input and performs any of the basic operation
(+, -, *, /) as per user requires.
Solution:
DECLARE FirstNumber, SecondNumber, Result: INTEGER
DECLARE Operation: CHAR
OUTPUT “Enter the first number”
INPUT FirstNumber
OUTPUT “Enter the second number”
INPUT SecondNumber
OUTPUT “Enter the operation”
INPUT Operation
CASE Operation OF
‘+’:
Result FirstNumber + SecondNumber
OUTPUT Result
‘-’:
Result FirstNumber - SecondNumber
OUTPUT Result
‘*’:
Result FirstNumber * SecondNumber
OUTPUT Result
‘/’:
Result FirstNumber / SecondNumber
OUTPUT Result
OTHERWISE
OUTPUT “Invalid operation”
ENDCASE
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Conditional Statements
Conditional Exercise 3
1
Write a pseudocode that takes from user: length, width and depth of an object. The
user also inputs the object code from the following table:
Object code
Object name
1
Square
2
Rectangle
3
Cylinder
Output the volume of the object based on the user’s choice.
HINT:
Volume of cylinder: π*r 2*depth
2
Design a program, using pseudocode and flowchart, that takes three numbers from the
user and prints the numbers in descending order.
3
Write a pseudocode that takes a number from the user and displays whether it’s a
negative or zero (don’t output anything if it’s positive).
1
Write a pseudocode that inputs the savings of a bank client without interest rate. The
program outputs the updated amount after applying interest according to the
following criteria:
 If savings exceed 500,000, the interest rate is 10%

If savings exceed 250,000, the interest rate is 5%

If savings exceed 50,000, the interest rate is 2.5%
 Otherwise no interest is added
If the user inputs a negative saving, an error message should be displayed and
the pr ogr am stops without calculating the updated amount .
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Conditional Statements
4
Write a pseudocode that inputs the income of a worker without taxes. The program
must output the updated amount after applying taxes according to the following
criteria:
Salary
Tax Rate
>10,000
50%
2,000 – 10,000
25%
<2,000
0%
Not e that the salary cannot b e less than 0 and not mo r e than 50,000
5
Write a pseudocode that reads two integer values (x and y), which should represent the
coordinates of a point in a plane. Next, determine which quadrant the point belongs.

If the point is at the origin print “Origin”


If it’s exactly on the x-axis print “X-Axis”
If it’s exactly on the y-axis print “Y-Axis”

Otherwise print the name of the quadrant
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Part I
FOR..NEXT
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Loop Statements
Definition of Iteration/Repetition:
One or more statements are repeated till a test condition is met or whilst a test condition is TRUE.
3.1 FOR … TO … NEXT
Definition:
A loop structure that iterates a set number of times.
FOR variable [initial value] TO [final value]
// statement(s) to be repeated
NEXT
Example 3.1.1:
Design pseudo-code and flowchart that prints the integers from 1 to 10.
Pseudocode solution:
FOR i  1 TO 10
OUTPUT i
NEXT
Flowchart solution:
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Loop Statements
E x a m p l e 3 .1.2:
Write pseudo-code that prints the integers from 10 to 1.
Pseudocode solution:
FOR Count  10 TO 1 STEP -1
OUTPUT Count
NEXT
Totaling
Definition:
Totaling is a process of summing a list of number.
Examples:
Total Total + 5
Sum Sum + Num
Example 3.1.3:
Write pseudocode that reads a number N, and prints the sum of all the numbers between 1
and N.
Pseudocode solution:
DECLARE N,Sum: INTEGER
O U T P U T “Enter the number ”
INPUT N
Sum 0
FOR i 1 TO N
Sum  Sum + i
NEXT
O U T P U T “T h e summat i on is: “, S u m
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Loop Statements
Counting
Definition:
Counting is the process of finding how many numbers/items are in a list.
Examples:
Count   Count + 1
Count   Count + 5
Count   Count – 1
Example 3.1.4:
Write pseudocode that inputs 50 numbers and counts the numbers that are greater than 100.
Pseudocode solution:
DECLARE Num,Count: INTEGER
Count   0
FOR i  1 TO 100
OUTPUT “Enter the number”
INPUT Num
IF Num > 100 THEN
Count   Count + 1
ENDIF
NEXT
OUTPUT “The count of numbers greater than 100 is: “,Count
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Loop Statements
Example 3.1.5:
Write pseudocode that reads 100 numbers and prints out their minimum.
Pseudocode solution 1:
DECLARE Min, Num: INTEGER
Min  99999
FOR Counter   1 TO 100
O U T P U T “Enter number”
INPUT Num
IF Num < Min THEN
Min Num
ENDIF
NEXT
O U T P U T “ M i n i m u m n u m b e r enter ed is: “ , Mi n
Pseudocode solution 2 (better solution):
DECLARE Min, Num: INTEGER
O U T P U T “Enter number”
INPUT Num
Min Num
FOR Counter   1 TO 99
O U T P U T “Enter number”
INPUT Num
IF Num < Min THEN
Min Num
ENDIF
NEXT
O U T P U T “ M i n i m u m n u m b e r enter ed is: “ , Mi n
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Loop Statements
Example 3.1.6:
Write pseudocode that reads 100 numbers and prints out their maximum.
Pseudocode solution 1:
DECLARE Max, Num: INTEGER
Max  -99999
FOR Counter   1 TO 100
O U T P U T “Enter number”
INPUT Num
IF Num > Max THEN
Max Num
ENDIF
NEXT
O U T P U T “M a x i m u m n u mb e r entered is: “,M a x
Pseudocode solution 2 (better solution):
DECLARE Max, Num: INTEGER
O U T P U T “Enter number”
INPUT Num
Max Num
FOR Counter   1 TO 99
O U T P U T “Enter number”
INPUT Num
IF Num > Max THEN
Max Num
ENDIF
NEXT
O U T P U T “M a x i m u m n u mb e r entered is: “,M a x
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Loop Statements
Loop Exercise 1
1
Write a pseudocode that prompts the user to enter a short message and the number of
times it is to be displayed and then displays the message the required number of times
2
Write a pesudocode that reads 100 numbers from the user. Then it counts the numbers
that in the range -100 to 35 inclusive.
3
Write a pseudocode that takes 5 numbers from the user and outputs the maximum.
4
Write a pseudocode to input 250 numbers. Count how many numbers are positive, how
many are negative and how many are zeros. Then output the results.
5
Write a pseudocode that inputs 500 numbers and outputs how many of these numbers
were whole numbers (integers).
HINT: You may use INT(x) in your answer. For example, INT(3.8) gives the value 3
6
Write a pseudocode that reads a number and prints out its factorial. The factorial of a
number is calculated by multiplying all the integers smaller than or equal to it until 1.
5! = 5 x 4 x 3 x 2 x 1
FACTORIAL CANNOT BE DONE ON A NEGATIVE NUMBER!
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Part II
WHILE..DO..ENDWHILE
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Loop Statements
3.2 WHILE ... DO ... ENDWHILE
Definition:
A loop that iterates whilst a specified condition exists
Criteria is pre-tested (It has criteria check at the start)
 It may never run
WHILE (CONDITION) DO
// Code to repeat in here.
ENDWHILE
Example 3.2.1:
Write pseudocode that reads set of numbers from the user until the user enters a non-positive
number (Less than or equal to zero). The program calculates and displays the total of these
numbers.
Pseudocode solution:
DECLARE Num: REAL
DECLARE Sum: REAL
Sum 0
OUTPUT “Input a number”
INPUT Num
WHILE Num >= 0 DO
Sum Sum + Num
OUTPUT “Input another number”
INPUT Num
ENDWHILE
OUTPUT “The sum of numbers entered is: “,Sum
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Loop Statements
Example 3.2.2:
Rewrite the pseudocode given below by using WHILE...DO...ENDWHILE loop
DECLARE Num, Total : INTEGER
INPUT N
Total   0
FOR i 1 TO N
Total Total + i
NEXT
OUTPUT Total
Pseudocode solution:
DECLARE Num, Total, i : INTEGER
INPUT Num
Total   0
i  1
WHILE i <= Num DO
Total Total + i
i   i+1
ENDWHILE
OUTPUT Total
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Part III
REPEAT..UNTIL
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Loop Statements
3.3 REPEAT … UNTIL
Definition:
A loop that iterates until a condition is met
Criteria is post-tested (It has criteria check at the end)
It iterates at least once
REPEAT
// code to repeat
UNTIL (STOPPING CONDITION)
Differences between REPEAT ... UNTIL and WHILE ... DO ... ENDWHILE:
In WHILE the criteria is pre-tested but in REPEAT..UNTIL the criteria is posttested
 WHILE may never run while REPEAT UNTIL runs at least once
WHILE iterates whilst a condition is TRUE but REPEAT UNTIL iterates till a
condition is TRUE
Example 3.3.1:
Design pseudocode that inputs set of until the user enters 0. Calculate and display the total.
Pseudocode solution:
DECLARE Sum: REAL
DECLARE num: REAL
Sum 0
REPEAT
OUTPUT “Enter a number to add”
INPUT num
Sum  Sum + num
UNTIL num = 0
OUTPUT “The total of the numbers entered: “,Sum
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Loop Statements
Example 3.3.2:
Write a pseudocode that will take anything as input and will display it as output until “Stop” or
“End” is pressed
Pseudocode solution:
REPEAT
OUTPUT “Enter a number, value, character or symbol to display”
INPUT anyvalue
OUTPUT anyvalue
UNTIL anyvalue = “End” OR anyvalue = “Stop”
Example 3.3.3:
Rewrite the pseudocode given below by using REPEAT .. UNTIL loop
DECLARE Num, Total : INTEGER
INPUT N
Total   0
FOR i 1 TO N
Total Total + i
NEXT
OUTPUT Total
Pseudocode solution:
DECLARE Num, Total, i : INTEGER
INPUT Num
Total   0
i  1
REPEAT
Total Total + i
i   i+1
UNTIL i > N
OUTPUT Total
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Loop Statements
IMPORTANT:
Both REPEAT..UNTIL and WHILE..DO..ENDWHILE loops are called Condition Controlled Loops
Purpose of Iteration/Repetition statements:
To repeat same or similar code a number of times, which allows for shorter code.
Loop Exercise 2
1
Write a pseudocode using that asks the user to enter an age between 1 and 99
inclusive and will validate the input. It should repeatedly ask the user for the age until
the user enters a valid age. The age is then displayed.
DO THIS QUESTION ONCE WITH WHILE AND ONCE WITH REPREAT UNTIL
2
Write a pseudocode that asks the user to input N weights from the user. The program
then prints the average of those weights.
VALIDATE THE WEIGHTS (CANNOT BE NEGATIVE OR MORE THAN 250)
DON’T FORGET TO VALIDATE N
3
4
Write a pseudocode that:

Inputs numbers till the user inputs -1

Totals the numbers that are between 40 and 80 (inclusive)
Suppose you have designed a game that only allows people to play it if they are over
12 years of age.
Write a pseudocode that reads ages of players until the user enters zero, and prints out
the number of players who can play the game, and the number of players who cannot.
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Loop Statements
5
Rewrite the following pseudocode using WHILE .. DO .. ENDWHILE and REPEAT..
UNTIL loop:
INPUT Num
Max Num
FOR Counter ← 1 TO 49
INPUT Num
IF Num > Max THEN
Max Num
ENDIF
NEXT
OUTPUT “The maximum number is :”,Max
6
Write a pseudocode that multiplies two numbers entered by the user without using the
multiplication operator.
7
Write a pseudocode that inputs username and password of an account on a social
network website. In order to return the password for an account, a function called
GetPassword(username) is used. This function takes a username as a parameter and
returns the corresponding password.
 The program displays “Success” if the password of the account is correct
 If the password is incorrect, the program prompts the user to re-enter the
password but only for 3 attempts
ASSUME THAT THE USERNAME ENTERED EXISTS IN THE SYSTEM
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Arrays
4.1 Arrays
Consider the following example:
Example 4.1:
Write a pseudocode that reads 5 numbers from the user and prints them in reverse order.
Pseudocode solution:
DECLARE Num1,Num2,Num3,Num4,Num5: INTEGER
INPUT Num1
INPUT Num2
INPUT Num3
INPUT Num4
INPUT Num5
OUTPUT Num5
OUTPUT Num4
OUTPUT Num3
OUTPUT Num2
OUTPUT Num1
This would be okay if you want to reverse few integers, but if you want to reverse 100 integers,
maybe a 1000. We have to use something called an Array.
Array Definition:
A data structure that holds a number of elements of the same data type.
Pseudocode declaration:
DECLARE Numbers[1:N] : INTEGER
N is the number of elements in the array
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Accessing an element in an array:
In order to access an element of the array, the index should be specified.
For example:
OUTPUT Numbers[1]
This statement will output the value stored in the first place in the array Nu mber s
Example 4.2:
Write pseudocode that reads 1000 numbers from the user and prints them in reverse order.
Pseudocode solution:
DECLARE Numbers[1: 1000] : INTEGER
F O R Counter  1 T O 1000
I N P U T N u mb er s[ C ou nt er ]
NEXT
F O R Counter  1000 T O 1 S T EP -1
O U T P U T N umbers[Counter ]
NEXT
Purpose of using arrays:
To store multiple values under the same identifier making the code shorter
Allows for simpler programming
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Example 4.3:
Write pseudocode that reads the ages of a 100 student from the user and stores them. Then
use the stored values to find the count of students who are older than 18 years.
Pseudocode solution:
DECLARE Ages[1:100]: INTEGER
DECLARE Count: INTEGER
FOR i  1 TO 100
INPUT Ages[i]
NEXT
Count   0
FOR i  1 TO 100
IF Ages[i] > 18 THEN
Count   Count + 1
ENDIF
NEXT
OUTPUT “Count of students older than 18 is: ”,Count
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Arrays
4.1 Associative Arrays
Sometimes you might need to store two values about a certain thing, for example, the name
and age of all students. In this case we’d need to have two arrays, one array for storing the
names, and one for storing the ages.
Example 4.4:
Write pseudocode that reads the names and marks of 50 students, stores them and then
output the name of the student who scored the highest grade. Marks are out of 100.
Pseudocode solution:
DECLARE Names[1:50]: STRING
DECLARE Marks[1:50]: INTEGER
DECLARE MaximumIndex, MaximumMark: INTEGER
MaximumMark  -1
FOR i  1 TO 50
OUTPUT “Enter the name of the student ”
INPUT Names[i]
REPEAT
OUTPUT “Enter the mark of the student ”
INPUT Marks[i]
UNTIL Marks[i]>=0 and Marks[i]<=100
NEXT
FOR i  1 TO 50
IF Marks[i] > MaximumMark THEN
MaximumMark   Marks[i]
MaximumIndex   i
ENDIF
NEXT
OUTPUT “Student with highest mark is : “,Names[MaximumIndex]
OUTPUT “The highest mark is:
“,MaximumMark
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Arrays
Arrays Exercise
1
Write a pseudocode that inputs and stores one temperature per day for a year (365
days).
Display:
The maximum temperature in the first 20 days
The maximum temperature in the last 20 days
2
Write pseudocode that will take 10 student names and 10 student ages and print the
name of the student with the maximum age.
3
A data logger records the temperature on a roof of a school twice a day, at midday and
midnight.
Task 1:

Input and store the temperatures recorded for 30 days.
o Y o u must store the temperatures in t wo arrays, o ne for mi dday
temperatures and one for midnight temperatures.

All temperatures should be validated and the user should repeatedly re-enter
the temperatures if they are invalid.
o Assume that a valid temperature is between -20 and 100
[5]
Task 2:

Calculate and output the average temperature for midday

Calculate and output the average temperature for midnight
[5]
Task 3:

Select the day with the highest midday temperature

Select the day with the lowest midnight temperature
Don’tforgettodisplayappropriatemessagesforinputandoutput.
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4
TASK 1
Input and store the names of 500 employees in a company. Also, input and store their
genders and salaries.

Gender is either “Male” or “Female”

Minimum salary is $1000 and maximum salary is $40,000
TASK 2
The program should display the name and salary of the top paid male worker and the
top paid female worker.
TASK 3
Determine and output who has higher average salary, male or female workers.
5
The height of buildings and number of floors in buildings were being analyzed.
Task 1:
Inputs the heights and number of floors of 200 buildings
o Heights should not be negative
o Number of floors cannot be less than 1 or more than 50
Task 2:
 Calculate and output the average height of all the buildings
Calculate and output the number of buildings with more than 50 floors
Task 3:
The user inputs number of floors and the program searches for buildings that
has the number of floors specified by the user and outputs the height of the
tallest one from those buildings.
(Note that: not all buildings will be considered when calculating the maximum)
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Arrays
6
Set up a voting system that chooses between 4 candidates. 50 students will vote.
Task 1:



Input and store the names of the 4 candidates
Output the candidate names with a number (1,2,3 or 4) beside each name
Set up another array for voting and set its value to zero
Task 2:


Each student inputs a choice between 1,2,3 or 4
Update the vote of the appropriate candidate

Output the name of the candidate voted for or output ‘invalid vote’ if a vote is
rejected
Task 3:

Display the name of the winner and the number of votes.
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13
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This pseudocode inputs the weight of items in kilograms to be loaded on a trailer. Any item over
25 kilograms is rejected. The trailer can take up to 100 kilograms.
TotalWeight   0
Rej ect   0
REPEAT
INPUT Weight
IF Weight > 25 THEN
Reject Reject + 1
ELSE
TotalWeight   TotalWeight + Weight
ENDIF
U N T IL TotalWeight > 100
TotalWeight   TotalWeight – Weight
OUTPUT “Weight of items ”’ TotalWeight ,” Number of items rejected “, Reject
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Databases
1. Data types used in database
Data Type
Examples
Number
12, 45, 1274, 653.12, -35.86
Currency
£12.45, -£0.01, €999.00, $5500
Text
DOG, ABC123, enquiries@bbc.co.uk
Boolean
TRUE/FALSE and YES/NO
Date
25/10/2007, 12 Mar 2008, 10-06-08
2. Selecting Data Types
When we input data to a database, we must analyse it and select appropriate data types for
each field:
Student Name:
Ben Smith
Text
Student Number:
1234
Number
Date of Birth:
10 July 1998
Date
Year Group:
6
Number
Special Diet:
Yes
Boolean
Height:
1.67
Number
Fees Paid:
$ 1500
Currency
3. Definition of Database
A structured collection of related data that allows people to extract information in a
w a y that me et s their needs.
Databases are very useful in preventing data problems occurring because:
Data is only stored once - no data duplication
 If any changes are made it only has to be done once - the data is consistent
Same data is used by everyone
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4. The structure of a database
Inside a database, data is stored in tables, which consists of many fields
and records.
The following table shows some database elements and their definitions:
Term
Definition
Examples
Table/File
A collection of related records
Table of students
For a student the fields
could include:
Student name
 Student ID
Age
 Address
Gender
Field
A column that contains one specific piece of
Field Name
Title given to each field and is always placed at
Record
A row within a table that contains data about a
Details (all information) of
single item, person or event
one student
Primary Key/
A field that contains unique data and can’t be
Key Field
repeated for more than one once
information and has one data type
the top row of table
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Databases
Note that:
Primary keys are used to:
To be sure that each record can be found easily
To prevent duplication of records
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Databases
5. Query By Example
In order to select data with some specific criteria from a database, we use queries.
Let’s consider the following example:
The following is a query-by-example grid:
Here, we enter the name of fields
that are involved in our search
We state here whether we need sorting
(Ascending/Descending) by a specific field
We write the table name of each
field. In our case it’s PROPERTY
Here, we write our
search criteria
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Databases
The following query-by-example grid selects and shows the Prices and Brochure numbers of all
houses with more than 1 bathroom and more than 2 bedrooms in ascending order of Price.
The results shown are:
399,000 H13
450,000 H10
6. Validation
Definition:
The automated checking by a program that data to be entered is sensible.
Examples of validation checks:
Type
Presence
 Range
 Length
Character
 Format
 Check digit
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5.1 Type Check
Definition:
Checks that the data entered has the appropriate data type.
Example:
A person’s age should be a number not text.
5.2 Presence Check
Definition:
Checks that some data has been entered and the value has not been left blank.
Example:
An email address must be given for an online transaction.
5.3 Range Check
Definition:
It checks that only numbers within a specified range are accepted.
Example:
Exam marks between 0 and 100 inclusive.
5.4 Length Check
Definition
It checks that data contains an exact number of characters
Example:
A password with exactly 8 characters in length. If the password has fewer or more than 8
characters, it will be rejected.
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Databases
5.6 Character Check
Definition:
It checks that a string of characters does not contain any invalid characters or symbols.
Examples:
A name would not contain characters such as %
A telephone number would only contain digits.
5.7 Format Check
Definition:
It checks that the characters entered conform to a pre-defined pattern.
Example:
A company with IDs that start with MS then three numbers would have a format of MS###
5.8 Check Digit
Definition:
A digit that it is calculated from all the other digits and appended to the number.
They can usually detect the following types of error:
An incorrect digit entered
o For example 5327 entered instead of 5307
Transposition errors where two numbers have changed order
o For example 5037 instead of 5307
Removing a digit
o For example 537 instead of 5307
Putting an extra digit
o For example: or 53107 instead of 530
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Example:
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7. Data Verification
Definition:
Checking that the data has not changed during input to a computer or during transfer
between computers.
Purpose:
To ensure the accuracy of transcription.
Verification methods include:
Screen/Visual check
Double entry
Screen/Visual Check
Definition:
 Data is compared visually with the source document by a user
The user is asked to confirm that the data entered is same as original
 If user finds a difference, the data is re-entered
Double Data Entry
Definition:
Data is entered twice (sometimes by two different people)
 A computer checks that both entries are equal
 If they are not equal, an error message requesting to re-enter the data is displayed
Note that:
Double data entry is different from Proofreading!
Proofreading is reading through the document, without referring to the original
source document, to identify grammatical and spelling mistakes.
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8. Testing Data
Definition:
Data used to check that a computer program responds correctly to correct and incorrect
data.
Normal
Definition
Examples
Correct data that should be accepted
The month can be any whole
Data
number in the range of 1 to 12
All the following values are not
allowed as inputs for the month:
Data outside the limits of acceptability,
Abnormal
or wrong type of data, and should be
Data
r ej ected
Negative numbers
Any value greater than 12
Letters or non-numeric data
Non-integer values
(e.g., 3.5,10.75, etc.)
Extreme
Data
Data at the limits of acceptability and it
The extreme values of month can
shoul d b e accept ed
be either 1 or 12
Boundary
Rejected
Data
The rejected data on the boundaries
Boundary rejected values of month
can be either 0 or 13
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Definitions
1. P r o g r a m
Definition:
A list of instructions that does a specific task
It can be written in High Level language or Low Level Language
2. P se ud oc o de
Definition:
Method that uses English words and mathematical notations to design the steps of a
program.
3. Flowcharts
Definition:
Diagram that designs the steps of a program by using a standard set of symbols joined by
lines to show the direction of flow.
4. Trace Table
Definition:
 Table that can be used to record the results from each step in an algorithm
It is used to record the value of a variable each time it changes
5. Variable
Definition:
A named data store that contains a value that can change during the execution of a program.
6. Constant
Definition:
A named data store that contains a value that does not change during the execution of a
program.
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Definitions
7. P r o g r a m d a t a t yp e s :
Definition
Examples
A positive or negative whole number be used in
150
mathematical operations
-100
Data type
Integer
A positive or negative number that has a
Real
100.5
fractional part that can be used in mathematical
-15.2
operations
Char
A single character from the keyboard
String
A sequence of characters
Boolean
Data with two possible values
H
Hello World
A312_@odq
TRUE/FALSE
8. S e q u e n t i a l s t a t eme n t s
Definition:
Statements are executed one after another according to their order.
9. Conditional/Selection st ate ment s
Definition:
Selective statement(s) are executed depending on meeting certain criteria.
Purpose:
To allow different paths through a program depending on meeting certain criteria.
10. IF .. THEN .. ELSE .. ENDIF
Definition:
A conditional structure with different outcomes for true and false.
Purpose:
It allows for checking complex conditions.
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Definitions
11. CASE .. OF .. OTHERWISE .. ENDCASE
Definition:
A conditional structure that allows selection to be made based on value of a variable.
Purpose:
Used to test for a large number of discrete values.
12 . Itera tive/Re pet ition s t a t e me n t s
Definition:
One or more statements are repeated till a test condition is met or whilst a test condition is
TRUE.
Purpose:
To repeat same or similar code a number of times, which allows for shorter code.
13. FOR .. TO .. NEXT
Definition:
A loop structure that iterates a set number of times.
14. WHILE .. DO .. ENDWHILE
Definition:
A loop that iterates whilst a specified condition exists
Criteria is pre-tested (It has criteria check at the start)
 It may never run
15. REPEAT .. UNTIL
Definition:
A loop that iterates until a condition is met
Criteria is post-tested (It has criteria check at the end)
It iterates at least once
Differences between REPEAT ... UNTIL and WHILE ... DO ... ENDWHILE:
In WHILE the criteria is pre-tested but in REPEAT..UNTIL the criteria is post-tested
WHILE may never run while REPEAT.. UNTIL runs at least once
WHILE iterates whilst a condition is TRUE but REPEAT UNTIL iterates till a condition is
TRUE
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Definitions
16. Totaling
Definition:
The process of summing a list of number.
Example:
Sum Sum + Num
17. Counting
Definition:
The process of finding how many items are in a list.
Example:
Count   Count + 1
18. Array
Definition:
A data structure that holds a number of elements of the same data type
Purpose:
To store multiple values under the same identifier making the code shorter
Allows for simpler programming
19. Top-Down design
Definition:
The breaking down of a computer system into set of sub systems and then breaking each
subsystem into set of smaller ones until each sub system performs a single action.
18. Structure C h a r t
Definition:
Diagram that shows the design of a computer system in a hierarchal way, with each level
giving a more detailed breakdown of the system.
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Definitions
19. Library routine
Definition:
It is a list of programming instructions that is:
Given a name
Already available for use
Pre-tested
Advantages of using library routines:
Library routines make writing programs easier and faster as the code is already written
 They make testing the program easier as the code has already been tested and
d eb u gged
20. Subroutine
Definition:
Set of programming statements for a given task and given a name
Subroutine is written in High Level Language
Can be procedure or function.
21. Function
Definition:
A subroutine that always returns a value.
22. Procedure
Definition:
A subroutine that doesn’t return a value.
23. Databas e
Definition:
A structured collection of related data that allows people to extract information in a way that
meets their needs.
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Definitions
2 4 . D a t a b a s e t e r ms :
Term
Definition
Examples
Table/File
A collection of related records
Table of students
For a student the fields
could include:
Student name
 Student ID
Age
 Address
Gender
Field
A column that contains one specific piece of
Field Name
Title given to each field
Record
A row within a table that contains data about a
Details (all information) of
single item, person or event
one student
Primary Key/
A field that contains unique data and can’t be
Key Field
repeated for more than one once
information and has one data type
Student ID field
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Definitions
25. Validation
Definition:
The automated checking by a program that data to be entered is sensible.
26. Examples of validation checks:
Validation
check
Type Check
Definition
Examples
Checks that the data entered has the
A person’s age should be
appropriate data type
a number not text.
An email address must be
Presence
Checks that some data has been entered
Check
and the value has not been left blank
Range Check
It checks that only numbers within a
Exam marks between 0
specified range are accepted
and 100 inclusive
Length Check
It checks that data contains an exact
A password with exactly 8
number of characters
characters in length
Character
It checks that a string of characters does not
A name would not contain
Check
contain any invalid characters or symbols
characters such as %
given for an online
transaction
A company with IDs that
Format Check
It checks that the characters entered
start with MS then three
conform to a pre-defined pattern
numbers would have a
format of MS###
Check Digit
A digit that it is calculated from all the other
digits and appended to the number
Used in barcodes
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26. Verification
Definition:
Checking that the data has not changed during input to a computer or during transfer between
computers.
Purpose:
To ensure the accuracy of transcription.
Types:
Screen/Visual Check
Double Data Entry
27. Screen/Visual Check
Definition:
 Data is compared visually with the source document by a user
The user is asked to confirm that the data entered is same as original
 If user finds a difference, the data is re-entered
28. Double Data Entry
Definition:
Data is entered twice (sometimes by two different people)
 A computer checks that both entries are equal
 If they are not equal, an error message requesting to re-enter the data is displayed
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29 . T e s t i n g d a t a
Definition:
Data used to check that a computer program responds correctly to correct and incorrect data.
30. T yp e s of test data:
Type
Definition
Examples
Normal
Correct data that should be accepted
The month can be any whole
Data
number in the range of 1 to 12
All the following values are not
allowed as inputs for the month:
Data outside the limits of acceptability,
Abnormal
or wrong type of data, and should be
Data
r ej ected
Negative numbers
Any value greater than 12
Letters or non-numeric data
Non-integer values
(e.g., 3.5,10.75, etc.)
Extreme
Data at the limits of acceptability and it
The extreme values of month can
shoul d b e accept ed
be either 1 or 12
Data
Boundary
Rejected
Data
The rejected data on the boundaries
Boundary rejected values of month
can be either 0 or 13
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