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01 c++ Intro.ppt
01 c++ Intro.ppt
01 c++ Intro.ppt
01 c++ Intro.ppt
01 c++ Intro.ppt
01 c++ Intro.ppt
01 c++ Intro.ppt
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01 c++ Intro.ppt

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  • 1. C++
  • 2. 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
    1
  • 3. 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
    1
  • 4. 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 )
    1
  • 5. 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
    1
  • 6. 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)
    1
  • 7. 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++
    1
  • 8. 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
    1
  • 9. 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
    1
  • 10. 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
    1
  • 11. 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
    1
  • 12. Common C++ Keywords
  • 13. 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
    1
  • 14. 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
    1
  • 15. 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
  • 16. 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
    1
  • 17. 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
    1
  • 18. 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
    1
  • 19. 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
    1
  • 20. 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
    1
  • 21. 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 (+) – subtraction (-)
      • multiplication (*) – division (/)
      • modulus (%)
    • 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
    2
  • 22. C++ Binary Arithmetic Operators 2
  • 23. 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
    2
  • 24. 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
    2
  • 25. 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
    2
  • 26. 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
    2
  • 27. Shortcut Arithmetic Operators
    • As you might expect, you can use two minus signs (--) before or after a variable to decrement it
    2
  • 28. 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
    2
  • 29. 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
    2
  • 30. 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 <<(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
    2
  • 31. Evaluating Boolean Expressions
    • The unary operator ! Means not, and essentially reverses the true/false value of an expression
    2
  • 32. 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
    2
  • 33. Some Sample Selection Statements within a C++ Program 2
  • 34. 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
    2
  • 35. The if Statement 2
  • 36. Multiple Executable Statement in an if-else 2
  • 37. The if Statement
    • Any C++ expression can be evaluated as part of an if statement
    2
  • 38. 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
    2
  • 39. The if Operator
    • 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
    2
  • 40. 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
    2
  • 41. Logical AND and Logical OR 2
  • 42. 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
    2
  • 43. 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
    2
  • 44. Using the Logical OR 2
  • 45. 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
    2
  • 46. A Typical Run of the Decisions.cpp Program 2
  • 47. 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
    2
  • 48. The while Loop 2
  • 49. The while Loop 2
  • 50. The for Statement
    • 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 ;
    2

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