Programming with Visual C++:
Concepts and Projects
Chapter 2A:
Reading, Processing and Displaying Data
(Concepts)
Objectives
In this chapter, you will:
• Develop algorithms to solve a problems
• Learn about the standard C++ data types
• Declare and initialize variables
• Read data using the TryParse() method
• Use the standard C++ arithmetic operators
Programming with Visual C++: Concepts and Projects
Objectives (continued)
• Process data using arithmetic expressions
• Abbreviate lines of code using shorthand
assignment operators
• Use the Math::Pow() and
Math::Sqrt() methods
• Display output using the ToString()
method
Programming with Visual C++: Concepts and Projects
Solving Problems
• An algorithm is an ordered list of steps
required to solve a problem
• Algorithms are written in pseudocode
• Algorithms are programming language
independent
– Written in English pseudocode
– Not written in a programming language
Programming with Visual C++: Concepts and Projects
Solving Problems (continued)
• High-level algorithms provide general list of
tasks (as shown in Algorithm 2-1)
• Low-level algorithms provide specific details
Programming with Visual C++: Concepts and Projects
Data and Data Types
• Data includes everything entered into your
program (numbers and characters for
example)
• Data is represented using binary digits called
bits
• A grouping of eight bits is called a byte
• Different kinds of data are called data types
Programming with Visual C++: Concepts and Projects
Data and Data Types (continued)
Programming with Visual C++: Concepts and Projects
Data and Data Types (continued)
Programming with Visual C++: Concepts and Projects
Data and Data Types (continued)
• Primitive data types
– Boolean (bool) used to represent true or false
– Character (char) represents a single character
• ASCII codes represent char data in one byte
– Integer (int) includes positive and negative whole
numbers and zero
– Real numbers (float and double) includes all
values that may have decimal places
• float – Represents single precision numbers
• double – Represents double-precision numbers
Programming with Visual C++: Concepts and Projects
Data and Data Types (continued)
Programming with Visual C++: Concepts and Projects
Data and Data Types (continued)
• Derived data types
• Built on primitive types
• The String data type is used to represent text
strings
• Text strings
• Example: “Hello world!”
Programming with Visual C++: Concepts and Projects
Variables
• A variable is a named location in memory that
stores data
• Variables are created by a process called
declaration
• When a variable is declared:
• One or more memory cells are allocated in
memory
• The allocated space is assigned a name
• The allocated space is associated with a data type
Programming with Visual C++: Concepts and Projects
Variables (continued)
• Variables may be declared on separate lines
• Or all on one line (if they are the same data
type)
Programming with Visual C++: Concepts and Projects
Variables (continued)
Programming with Visual C++: Concepts and Projects
Variables (continued)
• Examples of valid variable declarations
Programming with Visual C++: Concepts and Projects
Variables (continued)
• Variable naming conventions
• Names must begin with letter or underscore (_)
and can only use letters, digits or underscores in
the body of the name
• Names are case sensitive (height is not the
same name as Height)
• Spaces cannot be used as separators
Programming with Visual C++: Concepts and Projects
Variables (continued)
• Invalid variable names
Programming with Visual C++: Concepts and Projects
Variables (continued)
• Valid variable names
Programming with Visual C++: Concepts and Projects
Initializing Variables
• Initialization refers to the act of assigning a value to a
variable before it is used
• By default, Visual C++ initializes all numeric variables to
0 when the variable is declared
• The programmer can initialize variables using
assignment statements
Programming with Visual C++: Concepts and Projects
Initializing Variables (continued)
• Variables can also be initialized when they are declared
• In Example 2-5, num1 and num2 are declared as
integers.
– num1 is initialized to 0 by default
– num2 is initialized to 5
Programming with Visual C++: Concepts and Projects
Initializing Variables (continued)
Programming with Visual C++: Concepts and Projects
Data Input
• Data input refers to the process of reading
data from an object on the interface (like a
Textbox) into a variable
• Remember that variables exist in memory,
they are not the same as visible objects like
textboxes
Programming with Visual C++: Concepts and Projects
Data Input (continued)
Programming with Visual C++: Concepts and Projects
The TryParse() Method
• Used to get data from a TextBox on the
interface into a variable in the program’s
memory
• Parses the Text contained in a TextBox
• Parsing is the process of extracting data from a
string of text
• Every data type class has a built-in
TryParse() method
Programming with Visual C++: Concepts and Projects
The TryParse() Method
(continued)
• The scope resolution operator (::) identifies the data
type class that TryParse() belongs to (for example:
Int32)
• In Example 2-6 TryParse() is used to parse the
contents of textBox1->Text as a 32-bit integer
and assign the integer result to variable age
Programming with Visual C++: Concepts and Projects
The TryParse() Method
(continued)
• The TryParse() method makes use of
two parameters
– textBox1->Text
– age
• Parameters are items of information that a
method requires
• A parameter list is a groups of parameters
separated by commas
Programming with Visual C++: Concepts and Projects
The TryParse() Method
(continued)
Programming with Visual C++: Concepts and Projects
Data Processing
• Computations often involve arithmetic
expressions
• An arithmetic operator is a symbol that stands for
an arithmetic operation
• Arithmetic operations are
–
–
–
–
–
Multiplication (*)
Division (/)
Mod (%)
Addition (+)
Subtraction (-)
Programming with Visual C++: Concepts and Projects
Arithmetic Operators
• Operands are variables or values that arithmetic
operations are performed on
• Arithmetic operators are binary (require two
operands, one to the left and another to the right
of the operator)
• Arithmetic operations are performed from left to
right (left to right associative)
• Examples:
– num = num1 + num2;
– num = num + 1;
Programming with Visual C++: Concepts and Projects
Arithmetic Operators (continued)
Programming with Visual C++: Concepts and Projects
Arithmetic Operators (continued)
Programming with Visual C++: Concepts and Projects
Operator Precedence in Arithmetic
Expressions
• Complex arithmetic expressions have more than
one arithmetic operator
• Operator precedence rules dictate which
operations are performed first
• Multiplication (*), division (/) and mod (%) have
higher precedence than addition (+) and
subtraction (-)
• When two or more operators of the same
precedence are in an expression they are
performed from left to right
Programming with Visual C++: Concepts and Projects
Operator Precedence in Arithmetic
Expressions (continued)
Programming with Visual C++: Concepts and Projects
Operator Precedence in Arithmetic
Expressions (continued)
Programming with Visual C++: Concepts and
Projects
Operator Precedence in Arithmetic
Expressions (continued)
• Parentheses have higher precedence than all
arithmetic operators
• Parentheses can be used to perform lower
precedence operations before higher ones
• Expression trees are used to illustrate the
order in which operations are completed
when a complex expression is evaluated
Programming with Visual C++: Concepts and Projects
Operator Precedence in Arithmetic
Expressions (continued)
Programming with Visual C++: Concepts and Projects
Operator Precedence in Arithmetic
Expressions (continued)
Programming with Visual C++: Concepts and Projects
Arithmetic Operators and Strings
• Addition operator (+) is used to add numeric
data
• When the operator (+) is used with strings it
does not perform addition, instead, it joins the
strings together into one (this is called
concatenation)
• Example:
– textBox3->Text = textBox1->Text + textBox2->Text;
Programming with Visual C++: Concepts and Projects
Arithmetic Operators and Strings
(continued)
Programming with Visual C++: Concepts and Projects
Shorthand Assignment
• Shorthand operators are abbreviations for
assignment statements involving arithmetic
operations
• Shorthand operators: +=, /=, %=, +=, -=
• Example:
– The shorthand version of num1 = num1 + num2;
– is num1 += num2;
Programming with Visual C++: Concepts and Projects
The Math Library
• The system-defined Math class contains methods
that perform commonly-used tasks
• Example:
– To perform exponentiation (23)
• Math::Pow(2,3)
– To find the square root of 45
• Math::Sqrt(45)
– To find the length of the hypotenuse of a right triangle
• c=Math::Sqrt(Math::Pow(a,2)+Math:Pow(b,2));
Programming with Visual C++: Concepts and Projects
The Math Library (continued)
Programming with Visual C++: Concepts and Projects
The Math Library (continued)
• Common Math methods
–
–
–
–
–
Exponentiation, Math::Pow()
Square Root, Math::Sqrt()
Cosine, Math::Cos()
Sine, Math::Sin()
Tangent, Math::Tan()
• There are many others
Programming with Visual C++: Concepts and Projects
Data Output
• To display a value in the Text property of a
TextBox it must be converted to a String
• The ToString() method creates a string of
text from a non-text variable
• Every primitive data type in Visual C++ has a
built-in ToString() method
• Example:
– textBox3->Text = sum.ToString();
Programming with Visual C++: Concepts and Projects
Data Output (continued)
Programming with Visual C++: Concepts and Projects
Summary
• Solving problems requires algorithms
– Step-by-step lists of instructions
• Commonly used data types are
– Bool, char, int, float, and double
– The String data type stores character strings
• Data is stored in variables
• Variable declarations allocate, name and assign a
data type to memory cells
• Assignment statements are a common way to
initialize variables
Programming with Visual C++: Concepts and Projects
Summary (continued)
• Data Input
– Captures the contents of a TextBox and stores the
result in a variable
– TryParse()
• Data Processing
– Common arithmetic operations (*,/,%,+,-)
– Precedence rules (*,/ and % before +,-)
– Expression trees are used to evaluate arithmetic
expressions
Programming with Visual C++: Concepts and Projects
Summary (continued)
• Data Output
– Transferring data from a variable to a TextBox
– Use the ToString() method
Programming with Visual C++: Concepts and Projects