Lecture 1
A Review of Programming and C++
COSC1567
C++ Programming
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The Task of Programming
• Programming a computer involves writing
instructions that enable a computer to carry out
a single task or a group of tasks
• A computer programming language requires
learning both vocabulary and syntax
• Programmers use many different programming
languages, including BASIC, Pascal, COBOL,
RPG, and C++
• The rules of any language make up its syntax
• Machine language is the language that
computers can understand; it consists of 1s
and 0s
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The Task of Programming
• A translator (called either a compiler or an
interpreter) checks your program for syntax
errors
• A logical error occurs when you use a
statement that, although syntactically
correct, doesn’t do what you intended
• You run a program by issuing a command to
execute the program statements
• You test a program by using sample data to
determine whether the program results are
correct
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Programming Universals
• All programming languages provide methods for
directing output to a desired object, such as a
monitor screen, printer or file
• Similarly, all programming languages provide
methods for sending input into the computer
program so that it can be manipulated
• In addition, all programming languages provide for
naming locations in computer memory
• These locations commonly are called variables (or
attributes)
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Programming Universals
• Ideally, variables have meaningful names,
although no programming language actually
requires that they meet this standard
• A variable may have only one value at a time,
but it is the ability of memory variables to
change in value that makes computers and
programming worthwhile
• In many computer programming languages,
including C++, variables must be explicitly
declared, or given a data type as well as a
name, before they can be used
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Programming Universals
• The type determines what kind of values may
be stored in a variable
• Most computer languages allow at least two
types: one for numbers and one for
characters
• Numeric variables hold values like 13 or -6
• Character variables hold values like ‘A’ or ‘&’
• Many languages include even more
specialized types, such as integer (for
storing whole numbers) or floating point (for
storing numbers with decimal places)
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Procedural Programming
• Procedural programs consist of a series of steps or
procedures that take place one after the other
• The programmer determines the exact conditions
under which a procedure takes place, how often it
takes place, and when the program stops
• Programmers write procedural programs in many
programming languages, such as COBOL, BASIC,
FORTRAN, and RPG
• You can also write procedural programs in C++
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A main( ) Function in C++
• C++ programs consist of modules called
functions
• Every statement within every C++ program is
contained in a function
• Every function consists of two parts:
– A function header is the initial line of code in a C++
which always has three parts:
• Return type of the function
• Name of the function
• Types and names of any variables enclosed in
parentheses, and which the function receives
– A function body
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Creating a main( ) Function
• A C++ program may contain many functions,
but every C++ program contains at least one
function, and that function is called main( )
• If the main function does not pass values to
other programs or receives values from
outside the program, then main( ) receives
and returns a void type
• The body of every function in a C++ program
is contained in curly braces, also known as
curly brackets
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Creating a main( ) Function
• Every complete C++ statement ends with a
semicolon
• Often several statements must be grouped together,
as when several statements must occur in a loop
• In such a case, the statements have their own set of
opening and closing braces within the main braces,
forming a block
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Working with Variables
• In C++, you must name and give a type to
variables (sometimes called identifiers) before
you can use them
• Names of C++ variables can include letters,
numbers, and underscores, but must begin with
a letter or underscore
• No spaces or other special characters are
allowed within a C++ variable name
• Every programming language contains a few
vocabulary words, or keywords, that you need
in order to use the language
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Common C++ Keywords
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Working with Variables
• A C++ keyword cannot be used as a variable
name
• Each named variable must have a type
• C++ supports three simple types:
– Integer
— Floating point
— Character
• An integer is a whole number, either positive or
negative
• An integer value may be stored in an integer
variable declared with the keyword int
• You can also declare an integer variable using
short int and long int
13
Working with Variables
• Real or floating-point numbers are numbers
that include decimal positions, such as 98.6,
1000.00002, and -3.85
• They may be stored in variables with type float,
double, and long double
• Characters may be stored in variables declared
with the keyword char
• A character may hold any single symbol in the
ASCII character set
• Often it contains a letter of the alphabet, but it
could include a space, digit, punctuation mark,
arithmetic symbol, or other special symbol
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Working with Variables
• In C++, a character value is always expressed in
single quotes, such as ‘A’ or ‘&’
• To declare a variable, you list its type and its
name
• In addition, a variable declaration is a C++
statement, so it must end with a semicolon
• If you write a function that contains variables of
diverse types, each variable must be declared in
a statement of its own
• If you want to declare two or more variables of
the same type, you may declare them in the same
statement
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Working with Variables
• Explicitly stating the value of a variable is called
assignment, and is achieved with the assignment
operator =
• The variable finalScore is declared and assigned
a value at the same time
• Assigning a value to a variable upon creation is
often referred to as initializing the variable
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The const Qualifier
• A variable that does not change in a program
should not be declared as a variable
• Instead, it should be a constant
• The statement const double MINIMUM_WAGE =
5.75; declares a constant named
MINIMUM_WAGE that can be used like a
variable, but cannot be changed during a
program
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Creating Comments
• Comments are statements that do not affect the
compiling or running of a program
• Comments are simply explanatory remarks that
the programmer includes in a program to clarify
what is taking place
• These remarks are useful to later program
users because they might help explain the
intent of a particular statement or the purpose
of the entire program
• C++ supports both line comments and block
comments
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Creating Comments
• A line comment begins with two slashes (//) and
continues to the end of the line on which it is
placed
• A block comment begins with a single slash and an
asterisk (/*) and ends with an asterisk and a slash
(*/); it might be contained on a single line or
continued across many lines
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Using Libraries and
Preprocessor Directives
• Header files are files that contain predefined
values and routines, such as sqrt( )
• Their filenames usually end in .h
• In order for your C++ program to use these
predefined routines, you must include a
preprocessor directive, a statement that tells
the compiler what to do before compiling the
program
• In C++, all preprocessor directives begin with a
pound sign (#), which is also called an
octothorp
• The #include preprocessor directive tells the
compiler to include a file as part of the finished
product
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2
C++ Binary Arithmetic Operators
• Often after data values are input, you perform
calculations with them
• C++ provides five simple arithmetic operators for
creating arithmetic expressions:
– addition (+)
– multiplication (*)
– modulus (%)
– subtraction (-)
– division (/)
• Each of these arithmetic operators is a binary
operator; each takes two operands, one on each
side of the operator, as in 12 + 9 or 16.2*1.5
• The results of an arithmetic operation can be
stored in memory
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C++ Binary Arithmetic Operators
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C++ Binary Arithmetic Operators
• In Figure 2-2, each operation is assigned to a result
variable of the correct type
• The expression a + b has an integer result because
both a and b are integers, not because their sum is
stored in the intResult variable
• If the program contained the statement
doubleResult = a+b; the expression a+b would
still have an integer value, but the value would be
cast, or transformed, into a double when the sum is
assigned to doubleResult
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C++ Binary Arithmetic Operators
• The automatic cast that occurs when you assign
a value of one type to another is called an implicit
cast
• The modulus operator (%), which gives the
remainder of integer division, can be used only
with integers
• When more than one arithmetic operator is
included in an expression, then multiplication,
division, and modulus operations always occur
before addition or subtraction
• Multiplication, division, and modulus are said to
have higher precedence
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Shortcut Arithmetic Operators
• C++ employs several shortcut operators
• When you add two variable values and store the
result in a third variable, the expression takes the
form result= firstValue + secondValue
• When you use an expression like this, both
firstValue and secondValue retain their original
values; only the result is altered
• When you want to increase a value, the expression
takes the form firstValue = firstValue +
secondValue
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Shortcut Arithmetic Operators
• C++ provides the -= operator for subtracting
one value from another, the *= operator for
multiplying one value by another, and the /=
operator for dividing one value by another
• As with the += operator, you must not insert a
space within the subtraction, multiplication, or
division shortcut operators
• The options shown in Figure 2-4 means replace
the current value of count with the value that is
1 more than count, or simply increment count
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Shortcut Arithmetic Operators
• As you might expect, you can use two minus
signs (--) before or after a variable to decrement
it
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Shortcut Arithmetic Operators
• The prefix and postfix increment and decrement
operators are examples of unary operators
• Unary operators are those that require only one
operand, such as num in the expression ++num
• When an expression includes a prefix operator, the
mathematical operation takes place before the
expression is evaluated
• When an expression includes a postfix operator, the
mathematical operation takes place after the
expression is evaluated
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Shortcut Arithmetic Operators
• The difference between the results
produced by the prefix and postfix
operators can be subtle, but the
outcome of a program can vary greatly
depending on which increment
operator you use in an expression
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Evaluating Boolean Expressions
• A boolean expression is one that evaluates as true
or false
• All false relational expressions are evaluated as 0
• Thus, an expression such as 2>9 has the value 0
• You can prove that 2>9 is evaluated as 0 by entering
the statement code cout<<(2>9); into a C++ program
• A 0 appears on output
• All true relational expressions are evaluated as 1
• Thus, the expression 9>2 has the value 1
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Evaluating Boolean Expressions
• The unary operator ! Means not, and essentially reverses
the true/false value of an expression
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Selection
• Computer programs seem smart because of
their ability to use selections or make decisions
• C++ lets you perform selections in a number of
ways:
– The if statement
– The switch statement
– The if operator
– Logical AND and Logical OR
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Some Sample Selection
Statements within a C++ Program
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The if Statement
• If the execution of more than one statement depends on the
selection, then the statements must be blocked with curly
braces as shown in the code segment in Figure 2-8
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The if Statement
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Multiple Executable Statement
in an if-else
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The if Statement
• Any C++ expression can be evaluated as part of
an if statement
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The switch Statement
• When you want to create different outcomes depending
on specific values of a variable, you can use a series of
ifs shown in the program statement in Figure 2-14
• As an alternative to the long string of ifs shown in Figure
2-14, you can use the switch statement
• The switch can contain any number of cases in any
order
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The if Operator (NEW! )
Ex1-2.cpp
• Another alternative to the if statement involves the if
operator (also called the conditional operator), which is
represented by a question mark (?)
• E.g.
• cout<<(driveAge<26)?”The driver is under 26”:”The
driver is at least 26”;
• The if operator provides a concise way to express two
alternatives
• The conditional operator is an example of a ternary
operator, one that takes three operands instead of just
one or two
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Logical AND and Logical OR
• In some programming situations, two or more
conditions must be true to initiate an action
• Figure 2-16 works correctly using a nested if—
that is, one if statement within another if
statement
• If numVisits is not greater than 5, the statement
is finished—the second comparison does not
even take place
• Alternatively, a logical AND (&&) can be used,
as shown in Figure 2-17
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Logical AND and Logical OR
41
Logical AND and Logical OR
• A logical AND is a compound boolean expression in
which two conditions must be true for the entire
expression to evaluate as true
• Table 2-3 shows how an expression using && is
evaluated
• An entire expression is true only when the expression
on each side of the && is true
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Using the Logical OR
• In certain programming situations, only one of two
alternatives must be true for some action to take
place
• A logical OR (||) could also be used
• A logical OR is a compound boolean expression in
which either of two conditions must be true for the
entire expression to evaluate as true
• Table 2-4 shows how C++ evaluates any
expression that uses the || operator
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Using the Logical OR
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Using the Logical OR
• When either expression1 or expression2 is true (or
both are true), the entire expression is true
• On pages 53 and 54 of the textbook, perform the
steps so you can write a program that makes several
decisions
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A Typical Run of the
Decisions.cpp Program
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The while Loop
• Loops provide a mechanism with which to
perform statements repeatedly and, just as
important, to stop that performance when
warranted
while (boolean expression)
statement;
• In C++, the while statement can be used to loop
• The variable count, shown in the program in
Figure 2-21, is often called a loop-control
variable, because it is the value of count that
controls whether the loop body continues to
execute
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The while Loop
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The while Loop
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The for Statement
Ex1-3.cpp
• The for statement represents an alternative to the while
statement
• It is most often used in a definite loop, or a loop that must
execute a definite number of times
• It takes the form:
for (initialize; evaluate; alter)
statement;
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More examples
• Ex1-6.cpp
• Ex1-7.cpp
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Summary
• C++ provides five simple binary arithmetic
operators for creating arithmetic expressions:
addition (+), subtraction (-), multiplication (*),
division (/), and modulus (%)
• When you mix data types in a binary arithmetic
expression, the result is always the same type as
the type that takes the most memory to store
• C++ employs several shortcut operators for
arithmetic, such as +=, prefix, ++, and postfix ++
• A boolean expression is one that evaluates as
true or false
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Summary
• C++ uses the if, if-else, switch, and conditional
operator statements to make selections
• You can use the logical AND and OR to combine
boolean evaluations
• C++ uses the while statement, the do statement,
and the for loop to create loops
• Statements that depend on the boolean evaluation
in a decision or a loop are blocked by using curly
braces
• Fields contained within class objects are used in
arithmetic and boolean expressions in the same
manner as are primitive variables
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Summary
• C++ supports line comments and block
comments
• A preprocessor directive tells the compiler to
do something, such as to include a header
file, before compiling the program
• The cout statement (along with an insertion
operator) is used to display values
• When you create a class, you create your
own C++ data type, which is a complex type
composed of simpler types
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