Programming Chapter 2

//

Beginning of a comment

#

Beginning of preprocessor directive

<>

Enclose filename in #include

()

Used when naming a function

{}

Encloses a group of statements

“”

Encloses string of characters

;

End of programming statement

The cout Object

• Displays output on the computer screen

• You use the stream insertion operator («) to send output to cout

  • Ex. cout «“Programming is fun!”;

  • Can be used to send more than one item to cout

  • Ex. cout « “Hello” « “there!”; OR

  • cout « “Hello”;

  • cout « “there!”; which still produces one line of output

The endl Manipulator

• You can use the endl manipulator to start a new line of output. This will produce two lines of output

cout « “Programming is” « endl;

cout « “fun!”;

• DO NOT put quotation marks around endl

The \n Escape Sequence

• You can also use the \n escape sequence to state a new line of output. This will produce two lines of output:

cout « “Programming is\n”;

cout « “fun!’’;

*\n is inside the string!

The #include Directive

• Inserts the contents of another file into the program

• A preprocessor directive, not part of C++ language

• #include lines not seen by compiler

• DO NOT PLACE A SEMICOLON AT THE END OF #include line

Variable

A storage location in memory

• Has a name and a type of data it can hold

• Must be defined before it can be used: int item;

Literals

• a value that is written into a program’s code

  • String literal (“hello, there”)

  • 12 (integer literal)

Identifiers

A programmer-defined name for some part of a program (variables, functions, etc.)

YOU CANNOT USE ANY OF THE C++ KEY WORDS AS AN IDENTIFIER

Rules:

• The first character of an identifier must be an alphabetic character or an underscore

• After the first character you may use alphabetic characters, numbers, or underscore

• Upper- and lowercase characters are distinct

Defining Variables

Variables of the same time can be defined on separate lines (;;;) or the same line (,,;,;)

Variables of different types must be in different definitions

Integer Literals

An integer value that is typed into a program’s code (itemsOrdered = 15)

• Stored in memory as int by default

  • To store in a long memory location, put ‘L’ at the end of the number: 1234L

  • To store in a long long memory location, put ‘LL’ at the end of the number: 324LL

  • Constants that begin with ‘0’ are base 8: 075

  • Constants that begin with ‘0x’ are base 16: 0×75A

True or false: A variable name has no relation to the purpose of the variable

False, a variable name should represent the purpose of the variable

The char Data Type

• Used to hold characters of very small integer values

• Usually 1 byte of memory

• numeric value of character from the character set is stored in memory

  • Code: char letter; letter = ‘C’; Memory: letter 67

Character literals

• Must be enclosed in single quote marks (‘A’)

Character Strings

• A series of characters in consecutive memory locations (“Hello”)

• Stored with the null terminator (\0) at the end

• Comprised of the characters between the “” (H e l l o \0)

The C++ string Class

• Special data type supports working strings (# include <string>)

• Can define string variables in programs (string firstName, lastName;)

• Can receive values with assignment operator (firstName = “George”; lastName = “Washington”;)

• Can be displayed via cout (cout « firstName « “” « lastName;)

Floating-Point Data Types

Float, double, long double

• Can hold real numbers such as: 12.45, -3.8

• Stored in a form similar to scientific notation

• All floating-point numbers are signed

Floating Point Literals

• Can be represented in Fixed point (decimal) notation (31.4159) or E notation (3.14159E1)

• Are double by default

• Can be forced to be float (3.14159f) or long double (.0000625L)

The bool Data Type

• Represents values that are true or false

• bool variables are stored as small integers

• False is represented by 0, true by 1 (bool allDone = true; returns allDone 1)

Determining the Size of a Data Type

• the sizeof operator gives the size of any data type or variable

Variable assignments and initialization

• An assignment statement uses the = operator to store a value in a variable (item= 12; assigns the value 12 to the item variable)

• Assignment= the variable receiving the value must appear on the left side of the = operator.

True or false: this will work:

12 = item;

False, the variable receiving the value must appear on the left side of the = operator

Variable Initialization

• to initialize a variable means to assign it a value when it is defined (int length = 12;)

• Can initialize some or all variables (int length = 12, width = 5, area;)

Declaring Variables with the auto Key Word

• C++ 11 introduces an alternative way to define variables, using the auto key word and an initialization value (auto amount = 100; is an int)

• The auto key word tells the compiler to determine the variable’s data type from the initialization value.

Scope

• The scope of a variable is the part of the program in which the variable can be accessed

• A variable cannot be used before it is defined

Arithmetic Operators

• Used for performing numeric calculations

• C++ has unary, binary, and ternary opterators:

  • Unary (1 operand): -5

  • Binary (2 operands): 13 -17

  • Ternary (3 operands): exp1 ? Exp2 : exp3

• / (division) operator performs integer division if both operands are integers

  • If either operand is a floating point, the result is a floating point

• % (modulus) operator computes the remained resulting from integer division

  • requires integers for both operands (NO FLOATING POINTS)

Comments

• Used to document parts of the program

• Intended for persons reading the source code of the program

  • Indicate the purpose of the program

  • Describe the use of variables

  • Explain complex sections of code

• Are ignored by the compiler

Single-Line Comments

Begin with // through to the end of the line (Int length = 12; //length in inches OR // calculate rectangle area)

Multi-Line Comments

• Begin with /*, end with */

• Can span multiple lines

• Can begin and end on the same line

Named Constants

• Aka constant variable

• A variable whose content cannot be changed during program execution

• Used for representing constant balues with descriptive names

• Often named in uppercase letters

• “ const double TAX_RATE = 0.0675;

Programming Style

• The visual organization of the source code

• Includes the uses of spaces, tabs, and blank lines

• Does not affect the syntax of the program

• Affects the readability of the source code