1. Chapter 2 Beginning Problem-Solving Concepts for the Computer
CMPF144 Introduction to Problem Solving and Basic Computer

2. Overview Constants and Variables Data Types Functions Operators
Expressions and Equations

3. Objectives Differentiate between variables and constants.
Differentiate between character, numeric, and logical data types.
Identify operators, operands and resultants.
Identify and use functions
Identify and use operators according to placement in hierarchy chart.
Set up & evaluate expressions and equations using variables, constants, operators, and the hierarchy of operations.

4. Constant
A value (content in memory cell, can be alphabetic and/or numeric) that will never change during the execution of computer program
is referred to by its name (location of memory cell)
Name is given in CAPITAL LETTER to differentiate from variable
Example: PI = 3.142

5. Variable
A value (can be any data type)that might change during the execution of computer program
is referred to by its name
also known as identifier
there are rules for naming and using variables
Example:
number_of_student = ??
total_amount =??
depends on program execution

6. Rules for Naming and Using Variables
Name a variable according to what it represents.
Do not use spaces.
Start a variable name with a letter.
Do not use a dash or any other symbol that is used as a mathematical operator.
Consistent usage of variable name.
Consistent use of upper, lowercase characters in variable names
Use naming convention specified by your company

7. Incorrect Variable Names
Data Item
Incorrect Variable Name
Problem
Corrected Variable Name
Hours worked
Hours Worked
Space between words
HoursWorked
Name of client CN
Does not define data item
ClientName
Rate of pay
Rate-Pay
Uses a mathematical operator
PayRate
Quantity per customer
Quantity/Customer
QuantityPerCustomer
6% sales tax
6%_sales_tax
Starts with a number
SixPercentSalesTax @
SalesTax
Client address
Client_address_for_client_of_XYZ_corporation_in_California
Too long
ClientAddress
Variable name introduced as Hours
Hrs
Inconsistent name
Hours
Hours_worked
pp 51, WHAT’s WRONG WITH THIS? Q1

8. Data Type
a classification of the type of data that a variable or constant can hold in computer programming
Each data type consists of a set of permitted values, which is known as data set
Common categories of data type:
Numeric
Character
String
Logical
Date

9. Numeric Include all types of numbers
Can be used for numeric calculations
2 + 1 = ??
Subtypes include:
Integer
Whole number
Can be positive of negative
Example: 5297, -376
Real number
Also known as floating point numbers
Can be represented in scientific notation
Example: , 2.3E5 (2.3 x 105)

10. Numeric Data Types and Their Data Sets

11. Character / String
Consists of all single-digit numbers, letters and special characters available to the computer
Placed within quotation marks
Example: “a”, “2”, “=“
Cannot be used for calculation even though some are numbers
“2” + “1” = ??
Uppercase letter is different from lower case letter
“A” ≠ “a”
more than one character are combined together to form a string

12. Character / String (cont.)
Can be compared and sorted in alphabetical order (computer gives each character an ASCII number)
Banana > Apple
Joan > James
A < a
Can be joined together via concatenation (by using + operator)
“Hello” + “World” = “HelloWorld”
“4” + “4” = ??

13. Character / String Data Types and Their Data Sets

14. Logical Only consists of two value – True or False
Used to make yes-or-no decisions
Example:
result = True
badInput = “yes”
CreditOK = 1

15. Logical Data Types and Their Data Sets

16. Date
Is a numeric data type as mathematical operations can be performed onto the value
Allows user to subtract one date from another date

17. Examples of Data Types

18. Examples of Data Types (cont.)
pp. 47, QUESTIONS, Q5

19. Functions
Small sets of instructions that perform specific tasks and return values.
Requires parameter
General syntax : FunctionName (parameter)
Example: Sqrt(N) – What is this?? (╥﹏╥)
Syntax might vary for different programming language
Can be used repeatedly in a program to shorten the problem-solving time and increase program’s readability

20. Examples of Functions

21. Examples of Functions (cont.)

22. Examples of Functions (cont.)

23. Examples of Functions (cont.)

24. Operators
Tells the computer HOW to process data (example: add, subtract…)
Informs the computer WHAT type of processing (example: mathematical, logical…)
Two main concepts: OPERAND and RESULTANT
Types of operators:
Mathematical (standard mathematical calculation)
Relational (to program decision)
Logical (to connect relational expression and to perform operations on logical data)

25. Mathematical Operators and Their Computer Symbols

26. Relational Operators and Their Computer Symbols

27. Logical Operators and Their Computer Symbols

28. NOT Logical Operators

29. AND Logical Operators

30. OR Logical Operators
pp. 48, QUESTIONS, Q9

31. Hierarchy of Operations
pp. 48, QUESTIONS,
Q10

32. Expressions and Equations
Used to process data (operands) through operators
Example:
width * height
Equation:
Also known as assignment statements
Stores the resultant of an expression in a memory location of a computer through equal “=” symbol (assignment operator)
area = width * height

33. Expressions and Equations (cont.)

34. Setting Up a Numeric Expression
Mathematical expression:
X (3Y + 4) -
Appropriate computer representation: 4Y
X + 6
X * ( 3 * Y + 4) – 4 * Y / ( X + 6)
pp. 49, PROBLEMS, Q1

35. Setting Up a Mathematical Equation
Example:
Appropriate computer representation:
Only one variable on the left and an expression on the right of the “=” sign
Y + 3 = X ( Z + 5)
Y = X * ( Z + 5) - 3
pp. 49, PROBLEMS, Q2

36. Setting Up a Relational Expression
Given an expression :
Appropriate computer representation:
Computer can’t understand “is lesser than”
X is lesser than Y + 5
X < Y + 5

37. Evaluating a Mathematical Expression
pp. 49, PROBLEMS, Q5

38. Evaluating a Relational Expression

39. Evaluating a Logical Expression

40. Evaluating Equation That Uses Both Relational and Logical Operators
pp. 51, PROBLEMS, Q14

41. Developing a Table of All Possible Resultants of a Logical Expression
One unknown - A.
Two combinations:
A can be either True or False

42. Developing a Table of All Possible Resultants of a Logical Expression (cont.)
Two unknowns - A and B.
Four combinations:
B can be either True or False for each value of A.

43. Developing a Table of All Possible Resultants of a Logical Expression (cont.)
Three unknowns - A, B, and C.
Eight combinations.

44. Developing a Table of All Possible Resultants of a Logical Expression
pp. 50, PROBLEMS, Q13