week 3 chapter 3 expressions and interactivity n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
CS102 Introduction to Computer Programming PowerPoint Presentation
Download Presentation
CS102 Introduction to Computer Programming

Loading in 2 Seconds...

play fullscreen
1 / 61

CS102 Introduction to Computer Programming - PowerPoint PPT Presentation


  • 124 Views
  • Uploaded on

Week 3 Chapter 3 Expressions and Interactivity. CS102 Introduction to Computer Programming. Chapter 3 Expressions and Interactivity. The cin object Mathematical Expressions Automatic conversion and promotion Overflow and underflow The typecast operator The power of constants.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'CS102 Introduction to Computer Programming' - christophe


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
week 3 chapter 3 expressions and interactivity
Week 3

Chapter 3

Expressions and Interactivity

CS102Introduction to Computer Programming
chapter 3 expressions and interactivity
Chapter 3 Expressions and Interactivity
  • The cin object
  • Mathematical Expressions
  • Automatic conversion and promotion
  • Overflow and underflow
  • The typecast operator
  • The power of constants
  • Multiple assignments
  • Combined assignment operators
  • Formatting output with stream manipulators
  • Formatted input
  • More mathematical library functions
the cin object
The cin Object
  • cin is the standard input object
    • Causes the program to wait until information is typed at the keyboard and the enter key is pressed
    • Automatically converts the data read to the type of the variable used to store it
    • Truncates floating point numbers that are to be stored in integer variables
  • Notice the >> and << operators appear to point in the direction information is flowing.

Concept - The cin object reads information typed at the keyboard

program 3 1
Program 3-1

This program will calculate the area of any rectangle

#include <iostream.h>

void main(void)‏

{

int Length, Width, Area;

cout <<"This program calculates the";

cout <<" area of a rectangle.\n";

cout <<"What is the length of the ";

cout <<" rectangle? ";

cin >>Length;

cout <<"What is the width of the";

cout <<" rectangle? ";

cin>>Width;

Area = Length * Width;

cout <<"The area of the rectangle is "

cout << Area << ".\n";

}

Program Output

This program calculates the

area of a rectangle.

What is the length of the

rectangle?10 [Enter]

What is the width of the

rectangle?20 [Enter]

The area of the rectangle is 200.

program 3 2
Program 3-2

/* This program reads the length and width of a rectangle. It calculates the rectangle's area and displays the value on the screen. */

#include <iostream.h>

void main(void)‏

{

int Length, Width, Area;

cin >> Length;

cin >> Width;

Area = Length * Width;

cout << "The area of the rectangle is " << Area << endl;

}

This program does not let the user know what is needed as input.

Program Output

10 [Enter]

20 [Enter]

The area of the rectangle is 200.

the cin object1
The cin Object
  • Multiple values are separated by spaces
  • The Variables are assigned values in the order they are entered.
  • cin can read character strings into a properly defined variable
    • If the input string is too large, adjacent memory can be corrupted
    • Don't forget to leave room for the null character
    • The string can not contain spaces

Concept - The cin object can gather multiple values at once

program 3 3
Program 3-3

This program accepts multiple entries on one line

#include <iostream.h>

void main(void)‏

{

int Length, Width, Area;

cout <<"This program calculates";

cout <<" the area of a rectangle.\n";

cout <<"Enter the length and width";

cout <<" of the rectangle separated";

cout <<" by a space. \n";

cin >> Length >> Width;

Area = Length * Width;

cout <<"The area of the rectangle is ";

cout << Area << endl;

}

Program Output

This program calculates

the area of a rectangle.

Enter the length and width

of the rectangle separated

by a space.

10 20 [Enter]

The area of the rectangle is

200

program 3 4 or 3 3 version 4
Program 3-4 or3-3 version 4

/* This program demonstrates how cin can read multiple values of different data types. */

 #include <iostream.h>

 void main(void)‏

{

int Whole;

float Fractional;

char Letter;

cout << "Enter an integer, a float, ";

cout << "and a character: ";

cin >> Whole >> Fractional >> Letter;

cout << "Whole: " << Whole << endl;

cout << "Fractional: " << Fractional << endl;

cout << "Letter: " << Letter << endl;

}

Values of different data types can be

entered on the same line. They must be

entered in the correct order

Program Output

Enter an integer, a float,

and a character: 4 5.7 b [Enter]

Whole: 4

Fractional: 5.7

Letter: b

program 3 5 or 3 4 version 4
Program 3-5 or3-4 version 4

// This program demonstrates how cin can read a string into a character array. */

#include <iostream.h>

void main(void)‏

{

char Name[21];

cout << "What is your name? ";

cin >> Name;

cout << "Good morning ";

cout << Name << endl;

}

cin can read strings as well as numbers. Strings are stored in character arrays.

Program Output

What is your name? Charlie [Enter]

Good morning Charlie

program 3 6 or 3 5 version 4
Program 3-6 or3-5 version 4

Note that a space is used to separate the two inputs. If you want to read in a string with embedded spaces you can not use the cin command

// This program reads two strings

// into two character arrays.

#include <iostream.h>

void main(void)‏

{

char First[16], Last[16];

  cout << "Enter your first and last";

cout << " names and I will\n";

cout << "reverse them.\n";

cin >> First >> Last;

cout << Last << ", " << First;

cout <<endl;

}

Program Output

Enter your first and last

names and I will

reverse them.

Johnny Jones [Enter]

Jones, Johnny

notes on strings
Notes on strings:
  • If a character array is intended to hold strings, it must be at least one character larger than the largest string that will be stored in it.
  • The cin object will let the user enter a string larger than the array can hold. If this happens, the string will overflow the array’s boundaries and destroy other information in memory.
  • If you wish the user to enter a string that has spaces in it, you cannot use this input method.
check point 3 1
Check point 3.1
  • 3.1 What header file must be included in programs using cin?
  • 3.2 What type of variable is used to hold a C-string?
  • 3.3 Write a declaration statement for a character array named customer. It should be large enough to hold 52 characters in length.
  • 3.4 T or F: cin requires the user to press the [Enter] key when finished entering data
  • 3.5 Assume value is an integer variable. If the user enters 3.14 in response to the following programming statement, What will be stored in value
  • cin >> value;
    • 3.14
    • 3
    • 0
    • Nothing, an error message is displayed

<iostream>

char

char customer[53];

mathematical expressions
Mathematical Expressions
  • A mathematical expression is a programming statement that has a value
  • Consists of operators and their operands
    • operands can be constants or variables
  • Can be used by the cout object to display the value of the expression.

cout << (Operand1 operator Operand2);

Concept - C++ allows you to construct complex mathematical expressions using multiple operators and grouping symbols

program 3 7 or 3 6 version 4
Program 3-7 or3-6 version 4

Mathematical expressions can be used in cout statements.

Note the inputs are integers but they are converted to floats for storage

/* This program asks the user top enter the numerator and denominator of a fraction and it displays the decimal value*/

void main(void)‏

{

float Numerator, Denominator;

cout << "This program shows the ";

cout << "decimal value of a fraction.\n";

cout << "Enter the numerator: ";

cin >> Numerator;

cout << "Enter the denominator: ";

cin >> Denominator;

cout << "The decimal value is ";

cout << (Numerator / Denominator);

}

Program Output

This program shows the

decimal value of a fraction.

Enter the numerator: 3 [Enter]

Enter the denominator: 16 [Enter]

The decimal value is

0.1875

precedence
Precedence
  • If two operators share an operand the one with the highest precedence works first

highest - (Unary negation)‏

* / %

Lowest + -

  • Example 6 * 7 - 3 = 39 (not 24)‏
  • Example 3 + 12 / 3 = 7 (not 5 )‏

Mathematical expressions are evaluated left to right

associativity
Associativity
  • Associativity is either left to right or right to left
  • If two operators sharing an operand have the same precedence, they work according to their Associativity.

Right to left - (Unary negation)‏

left to right * / %

left to right + -

Associativity is the order in which an operator works with its operands

grouping with parentheses
Grouping With Parentheses
  • Parentheses are used to force some operations to be performed before others
    • examples:

(5+2)*4 = 28

10 / (5-3) = 5

(4 + 17 ) % 2 -1 = 0

no exponents please
No Exponents Please
  • Include the following file in your program to deal with exponents:

#include <cmath> (or math.h, old way)‏

  • Use the pow function to raise a value (x) to the power (y) (x and y may be int or float)‏
  • example: the area of a circle is (radius2)‏

Area = 3.14 * pow(radius,2);

  • The pow function returns a double

Concept - C++ does not have an operator to raise a number to a power. A library function must be used

program 3 8 or 3 7 version 4
Program 3-8 or3-7 version 4

/*This program calculates the area of a circle. The formula for the radius of a circle is Pi times the radius squared Pi is 3.14159 */

#include <iostream.h>

#include <math.h>

void main(void)‏

{

double Area, Radius;

cout << "This program calculates the ";

cout << " area of a circle.\n";

cout << "What is the radius of ";

cout << "the circle? ";

cin >> Radius;

Area = 3.14159 * pow(Radius,2);

cout << "The area is " << Area;

}

This program uses the pow function to find the area of a circle

Program Output

This program calculates the

area of a circle.

What is the radius of the

circle?

10 [Enter]

The area is 314.159

check point 3 2
Check Point 3.2

3.11 Write C++ expressions for the following algebraic expressions:

y = 6x

a = 2b + 4c

y = x2

x + 2

g =---------

z2

  • 3.10 Complete the table below by writing the value of each expression in the "Value" column.
  • Expression Value
  • 6 + 3 * 5
  • 12 / 2 – 4
  • 9 + 14 * 2 – 6
  • 5 + 19 % 3 – 1
  • (6 + 2 ) * 3

y = 6 * x;

21

2

a = (2 * b ) + (4 * c ) ;

31

5

y = pow( x,2);

24

g = (x + 2) / pow( z,2);

3 3 when you mix apples and oranges type coercion rules
3.3 When you Mix Apples and Oranges:Type Coercion Rules
  • Rule 1 - Chars,shorts, and unsigned shorts are automatically promoted to int.
  • Rule 2 - If two values are of different types the lower-ranking one is promoted to the type of the higher-ranking on
  • Rule 3 - when the value of an expression is assigned to a variable it will be converted to the data type of the variable

Concept - When an operator's operands are of different data types, C++ will automatically convert them to the same data type

3 4 overflow and underflow
3.4 Overflow and Underflow
  • When a variable is assigned a value that is too large or too small in range for that variable’s data type, the variable overflows or underflows.
    • Overflow - when a variable is assigned a number that is too large for its data type
    • Underflow - when a variable is assigned a number that is too small for its data type
overflow and underflow
Overflow and Underflow
  • If an integer variable overflows or underflows the value wraps back around
    • no warning or error message is generated
  • If a floating point variable overflows or underflows the result depends on the compiler.

Concept - When a variable is assigned a value that is too large or too small in range for that variables data type, the variable underflows or overflows

program 3 9 or 3 8 version 4
Program 3-9 or3-8 version 4

//This program demonstrates integer overflow and underflow

#include <iostream.h>

void main(void)‏

{

short TestVar = 32767;

cout << TestVar << endl;

TestVar = TestVar + 1;

cout << TestVar << endl;

TestVar = TestVar - 1;

cout << TestVar << endl;

}

This program assumes that an integer is stored in two bytes of memory

Program Output

32767

-32768

32767

program 3 10 or 3 9 version 4
Program 3-10 or3-9 version 4

//This program can be used to see

// how your system handles floating

// point overflow and underflow.

#include <iostream.h>

void main(void)‏

{

float Test;

Test = 2.0e38 * 1000;

// Should overflow Test

cout << Test << endl;

Test = 2.0e-38 / 2.0e38;

// Should underflow Test

cout << Test << endl;

}

This compiler does not generate a runtime error but the value stored may not be usable

Program Output

1.#INF

0

3 5 the typecast operator
3.5 The Typecast Operator
  • The typecast operator manually promotes or demotes a value
    • works on either an expression or a variable
    • the conversion is temporary
    • truncation may occur

Example:

Val = int(number);

Val = float(digit1) / digit2; //prevents integer divide

Val = float (digit1/digit2); //allows integer divide

Val = (int) number; // is also correct

program 3 11 or 3 10 version 4
Program 3-11 or3-10 version 4

This program uses the type cast operator to avoid integer division

#include <iostream.h>

void main(void)‏

{

int Months, Books;

float PerMonth;

cout << "How many books do you ";

cout << "plan to read? ";

cin >> Books;

cout << "How many months will ";

cout << "it take you to read them? ";

cin >> Months;

PerMonth = float(Books) / Months;

cout << "That is " << PerMonth

cout << " books per month.\n";

Program Output

How many books do you

plan to read?

30 [Enter]

How many months will

it take you to read them?

7 [Enter]

That is 4.285714

books per month.

typecast warnings
Typecast Warnings
  • In Program 3-11, the following statement would still have resulted in integer division:

PerMonth = float(Books / Months);

  • Because the division is performed first and then the result is type cast to a float.
  • Type casting has no effect on the values it operates on. A temporary variable is created for the duration of the instruction.
program 3 12 or 3 11 version 4
Program 3-12 or3-11 version 4

/* This program uses a typecast operator to print a character from a number.*/

#include <iostream.h>

void main(void)‏

{

int Number = 65;

cout << Number << endl;

cout << char(Number) << endl;

}

Program Output

65

A

the power of constants
The Power of Constants
  • Makes the program more readable
  • Simplifies maintenance

Example:

const float PI = 3.14159;

or

#define PI 3.14159

  • Using a named constant will not make the program run more efficiently

Concept - Constants may be given names that symbolically represent them in a program

program 3 13 or 3 12 version 4
Program 3-13 or3-12 version 4

The literal 3.14159 has been replaced with a floating point constant.

#include <iostream.h>

#include <math.h>

void main(void)‏

{

const float Pi = 3.14159;

double Area, Radius;

cout << "This program calculates"; cout << " the area of a circle.\n";

cout << "What is the radius of ";

cout << " the circle? ";

cin >> Radius;

Area = Pi * pow(Radius,2);

cout << "The area is " << Area;

}

Program Output

This program calculates

the area of a circle.

What is the radius of

the circle?

5 [Enter]

The area is 78.5397

the define directive
The #define Directive
  • The older C-style method of creating named constants is with the #define directive, although it is preferable to use the const modifier.

#define PI 3.14159

  • is roughly the same as

const float PI=3.14159;

program 3 14 or 3 13 version 4
Program 3-14 or3-13 version 4

Remember that the preprocessor performs a textual substitution. So each instance of Pi becomes a floating point literal.

#include <iostream.h>

#include <math.h>

// needed for pow function

#define PI 3.14159

void main(void)‏

{

double Area, Radius;

cout << "This program calculates";

cout << " the area of a circle.\n";

cout << "What is the radius of the";

cout << " circle? ";

cin >> Radius;

Area = PI * pow(Radius, 2);

cout << "The area is " << Area;

}

Program Output

This program calculates

the area of a circle.

What is the radius of the

circle?

5 [Enter]

The area is 78.5397

multiple assignments
Multiple Assignments
  • Groups like-variables in one statement
  • May be used within an expression
    • has the lowest precedence of all arithmetic operations
    • Should be placed within parentheses
  • May be confusing if not clearly documented

Example:

a = b = c = d = 12

/

Concept - Multiple assignment means to assign the same value to several variables with one statement.

combined assignment operators
Combined Assignment Operators
  • Eliminates the need to enter the variable name twice

Operator Example usage Equivalent to

+= x += 5; x = x + 5;

-= y -=2; y = y - 2;

*= z *= 10; z = z * 10;

/= a /=b; a = a / b;

%= c %= 3; c = c % 3;

Concept - The combined assignment operators make common arithmetic operations easier

3 8 formatting output with string manipulation
3.8 Formatting Output WithString Manipulation
  • setw(n) n = the width of the display
  • setprecision(n) n = the number of significant digits or decimal places displayed
  • flags:
      • left
      • right
      • fixed
  • dec
  • hex
  • oct
  • scientific
  • showpoint
  • showpos
  • uppercase

Concept - The cout object provides ways to format data as it is being displayed.

program 3 17 or 3 15 version 4
Program 3-17 or3-15 version 4

//This program displays three rows of numbers

#include<iostream.h> 

void main(void)‏

{

int Num1 = 2897, Num2 = 5, Num3 = 837,

Num4 = 34, Num5 = 7, Num6 = 1623,

Num7 = 390, Num8 = 3456, Num9 = 12;

// Display the first row of numbers

cout << Num1 << " ";

cout << Num2 << " ";

cout << Num3 << endl;

// Display the second row of numbers

cout << Num4 << " ";

cout << Num5 << " ";

cout << Num6 << endl;

// Display the third row of numbers

cout << Num7 << " ";

cout << Num8 << " ";

cout << Num9 << endl;

}

This program displays values with no output formatting. There is no column alignment.

Program Output

2897 5 837

34 7 1623

390 3456 12

program 3 18 or 3 16 version 4
Program 3-18 or3-16 version 4

The setw command is used to line up the columns. The default is right justified

/*This program displays three rows of numbers. */

#include <iostream.h>

#include <iomanip.h>

void main(void)‏

{

int Num1 = 2897, Num2 = 5, Num3 = 837,

Num4 = 34, Num5 = 7, Num6 = 1623,

Num7 = 390, Num8 = 3456,

Num9 = 12;

// Display the first row of numbers

cout << setw(4) << Num1 << " ";

cout << setw(4) << Num2 << " ";

cout << setw(4) << Num3 << endl;

// Display the second row of numbers

cout << setw(4) << Num4 << " ";

cout a<< setw(4) << Num5 << " ";

cout << setw(4) << Num6 << endl;

// Display the third row of numbers

cout << setw(4) << Num7 << " ";

cout << setw(4) << Num8 << " ";

cout << setw(4) << Num9 << endl;

}

Program Output

2897 5 837

34 7 1623

390 3456 12

program 3 19 or 3 17 version 4
Program 3-19 or3-17 version 4

/* This program demonstrates the setw manipulator being used with values of various data types. */

#include <iostream.h>

#include <iomanip.h>

void main(void)‏

{

int IntValue = 3928;

float FloatValue = 91.5;

char StringValue[14] = "John J. Smith";

cout << "(" << setw(5);

cout << IntValue << ")" << endl;

cout << "(" << setw(8);

cout << FloatValue << ")" << endl;

cout << "(" << setw(16);

cout << StringValue << ")" << endl;

}

setw can format the output of any data type

Program Output

( 3928)‏

( 91.5)‏

( John J. Smith)‏

precision
Precision
  • Floating point values may be rounded to a number of significant digits, or precision, which is the total number of digits that appear before and after the decimal point.
program 3 20 or 3 18 version 4
Program 3-20 or3-18 version 4

/* This program demonstrates how setprecision rounds floating point value. */ 

#include <iostream.h>

#include <iomanip.h>

void main(void)‏

{

float Quotient, Number1 = 132.364,

Number2 = 26.91;Quotient = Number1 / Number2;cout << Quotient << endl;cout << setprecision(5) << Quotient << endl;cout << setprecision(4) << Quotient << endl;cout << setprecision(3) << Quotient << endl;cout << setprecision(2) << Quotient << endl;cout << setprecision(1) << Quotient << endl;

}

setprecision does not truncate numbers it rounds them up

Program Output

4.91877

4.9188

4.919

4.92

4.9

5

table 3 11
Table 3-11

Number Manipulator Value Displayed

28.92786 setprecision(3) 28.9

21. setprecision(5) 21

109.5 setprecision(4) 109.5

34.28596 setprecision(2) 34

cout << fixed;

28.92786 setprecision(3) 28.928

21. setprecision(5) 21.00000

109.5 setprecision(4) 109.5000

34.28596 setprecision(2) 34.29

program 3 21 or 3 19 version 4
Program 3-21 or3-19 version 4

This program will display 5 significant digits. But what if the total takes 6

/* This program asks for sales figures for 3 days. The total sales is calculated and displayed in a table*/

#include <iostream>

#include <iomanip>

Using namespace std;

int main()‏

{

float Day1, Day2, Day3, Total;

cout << "Enter the sales for day 1: ";

cin >> Day1;

cout << "Enter the sales for day 2: ";

cin >> Day2;

cout << "Enter the sales for day 3: ";

cin >> Day3;

Total = Day1 + Day2 + Day3;

cout << "\nSales Figures\n";

cout << "-------------\n";

cout << setprecision(5);

cout << "Day 1: " << setw(8) << Day1;

cout << endl;

cout << "Day 2: " << setw(8) << Day2;

cout << endl;

cout << "Day 3: " << setw(8) << Day3;

cout << endl;

cout << "Total: " << setw(8) << Total;

cout << endl;

return 0;

}

program output
Program Output

Enter the sales for day 1: 321.57 [Enter]

Enter the sales for day 2: 269.62 [Enter]

Enter the sales for day 3: 1307.77 [Enter]

Sales Figures

-------------

Day 1: 321.57

Day 2: 269.62

Day 3: 1307.8

Total: 1899 The value has been truncated

program 3 22 or 3 20 version 4
Program 3-22 or3-20 version 4

Program Output (modified)

Enter the sales for day 1: 321.00 [Enter]

Enter the sales for day 2: 869.26 [Enter]

Enter the sales for day 3: 403.77 [Enter]

Sales Figures

-------------

Day 1: 321

Day 2: 869.26

Day 3: 403.77

Total: 1594.90

#include <iostream>

#include <iomanip>

using namespace std;

int main()‏

{

float Day1, Day2, Day3, Total;

cout << "Enter the sales for day 1: ";

cin >> Day1;

cout << "Enter the sales for day 2: ";

cin >> Day2;

cout << "Enter the sales for day 3: ";

cin >> Day3;

Total = Day1 + Day2 + Day3;

cout << "\nSales Figures\n";

cout << "------\n";

cout << setprecision(2) << fixed << showpoint;

cout << "Day 1: " << setw(8) << Day1 << endl;

cout << "Day 2: " << setw(8) << Day2 << endl;

cout << "Day 3: " << setw(8) << Day3 << endl;

cout << "Total: " << setw(8) << Total << endl;

return 0;

}

The decimal point is displayed only if there are digits to the right of it.

stream manipulator
Stream Manipulator

fixed Displays floating-point numbers in fixed point notation.

setw(n) Establishes a print field of n spaces.

showpoint Causes a decimal point and trailing zeros to be displayed, even if there is no fractional part.

setprecision(n) Sets the precision of floating-point numbers

left Causes subsequent output to be left justified.

right Causes subsequent output to be right justified.

important points about the way cin handles field widths
Important points about the way cin handles field widths:
  • The field width only pertains to the very next item entered by the user.
  • cin stops reading input when it encounters a whitespace character or when it has all the character it needs.
    • White space characters include the [Enter] key, space, and tab.
program 3 28 or 3 22 version 4
Program 3-28 or3-22 version 4

// This program demonstrates cin's

// getline member function.

#include <iostream.h>

#include <iomanip.h>

void main(void)‏

{

char String[81];

cout << "Enter a sentence: ";

cin.getline(String, 81);

cout << "You entered ";

cout << String << endl;

}

cin.getline will read one less character than the second parameter specifies to make room for the NULL character

Program Output

Enter a sentence:

To be, or not to be. [Enter]

You entered

To be, or not to be.

program 3 29 or 3 23 version 4
Program 3-29 or3-23 version 4

cin requires that the user enter only a single. non white space character. All other input is ignored.

#include <iostream.h>

#include <iomanip.h>

void main(void)‏

{

char Ch;

cout << "Type a character

cout << " and press

cout << " Enter: ";

cin >> Ch;

cout << "You entered " << Ch << endl;

}

Program Output

Type a character

and press

Enter:

A [Enter]

You entered

A

program 3 30 or 3 23 version 4
Program 3-30 or3-23 version 4

#include <iostream.h>

#include <iomanip.h>

 void main(void)‏

{

char Ch;

cout << "This program has"; cout << " paused. Press";

cout << " enter to continue.";

cin.get(Ch);

cout << "Thank you!";

cout << endl;

}

cin.get will accept any key, particularly the return key

Program Output

This program has

paused. Press

Enter to continue.

[Enter]

Thank you!

program 3 31 or 3 23 version 4
Program 3-31 or3-23? version 4

#include <iostream.h>

#include <iomanip.h>

void main(void)‏

{

char Ch;

cout << "Type a character"; cout << " and press Enter: ";

cin.get(Ch);

cout << "You entered ";

cout << Ch << endl;

cout << "Its ASCII code is ";

cout << int(Ch) << endl;

}

cin.get will accept non printable and white space characters

Program Output

Type a character and press Enter: [Enter]

You entered

Its ASCII code is

10

mixing cin and cin get
Mixing cin and cin.get
  • Mixing cin.get with cin can cause an annoying and hard-to-find problem.
  • Pressing the [Enter] key after inputting a number will cause the newline character to be stored in the keyboard buffer. To avoid this, use cin.ignore:
  • cin.ignore(20,’\n’); // will skip the next 20 chars in the input buffer or until a newline is encountered, whichever comes first
  • cin.ignore(); //will skip the very next character in the input buffer
more mathematical library functions
More Mathematical Library Functions
  • cos
    • cosine
  • sin
    • sine
  • tan
    • tangent
  • abs

Absolute Value

  • exp

ex

  • fmod
    • modulus for floating point
  • log
    • natural log
  • log10
    • base 10 log
  • sqrt
    • square root

Concept - The C++ runtime library provides several functions for performing complex mathematical operations.

table 3 14 or 3 13 version 4
Table 3-14 or3-13 version 4

abs y = abs(x);

Returns the absolute value of the argument. The argument and the return value are integers.

cos y = cos(x);

Returns the cosine of the argument. The argument should be an angle expressed in radians. The return type and the argument are doubles.

exp y = exp(x);

Computes the exponential function of the argument, which is x. The return type and the argument are doubles.

table 3 14 continued or 3 13 version 4
Table 3-14 continued or3-13 version 4

fmod y = fmod(x, z);

Returns, as a double, the remainder of the first argument divided by the second argument.

log y = log(x);

Returns the natural logarithm of the argument. The return type and the argument are doubles.

log10 y = log10(x);

Returns the base-10 logarithm of the argument. The return type and the argument are doubles.

table 3 14 continued or 3 13 version 41
Table 3-14 continued or3-13 version 4

sin y = sin(x);

Returns the sine of the argument. The argument should be an angle expressed in radians. The return type and the argument are doubles.

sqrt y = sqrt(x);

Returns the square root of the argument. The return type and argument are doubles.

tan y = tan(x);

Returns the tangent of the argument. The argument should be an angle expressed in radians. The return type and the argument are doubles.

program 3 32 or 3 24 version 4
Program 3-32 or3-24 version 4

This program uses the sqrt function to find the hypotenuse of a right triangle

#include <iostream.h>

#include <math.h> // For sqrt

void main(void)‏

{

float A, B, C;

cout << "Enter the length of side A: ";

cin >> A;

cout << "Enter the length of side B: ";

cin >> B;

C = sqrt(pow(A, 2.0) + pow(B, 2.0));

cout.precision(2);

cout << "The length of the ";

cout << "hypotenuse is "<< C << endl;

}

Program Output

Enter the length of side

A: 5.0 [Enter]

Enter the length of side B:

12.0 [Enter]

The length of the

hypotenuse is 13

random numbers
Random Numbers

y = rand(); (from the stdlib.h library)‏

  • returns pseudo-random number
  • C++ returns the same sequence of numbers each time the program executes

srand(x); (from the stdlib.h library)‏

  • seeds the random number generator so that a new sequence of numbers will be generated

Concept - Some programming techniques require the use of randomly generated numbers

program 3 33 or 3 25 version 4
Program 3-33 or3-25 version 4

// This program demonstrates random

//numbers.

 #include <iostream.h>

#include <stdlib.h>

void main(void)‏

{

unsigned Seed;

cout << "Enter a seed value: ";

cin >> Seed;

srand(Seed);

cout << rand() << endl;

cout << rand() << endl;

cout << rand() << endl;

}

It still gives the same numbers for the same seed value

Program Output

Enter a seed value: 5

1731

32036

21622

Program Output with Other Example Input

Enter a seed value: 16

5540

29663

9920

basic file i o
Basic File I/O
  • The file fstream.h contains all the declarations necessary for file operations

#include <fstream.h>

  • It declares the following data types
    • ofstream used to open a file for output
    • ifstream used to open a file for input
    • fstream used to open a file for both input and output
  • You must declare an object of one of these data types

i.e ifstream InputFile;

reading from a file
Reading from a file
  • Once the file has been opened you can read data from it similar to the way cin is used

InputFile >> Variable_Name

  • The data is read in the order found in the file
  • You can create a file using notepad or any other word processor.
  • Make sure the file name matches the file name in the open statement exactly
  • The file must be in the same directory that the executable file is located or you will need to specify the exact path.