ch2-Streams

Chapter_2                                                                                               ch2-Strings 

Contents:

Declare.cpp     Hello.cpp     Exercise_2-1     Stream.cpp     Concat.cpp     Numconv.cpp     Exercise_2-2     CallHello.cpp

Declare.cpp     TCP1, p. 93-94     (Declaration & definition examples)     download

// Declaration & definition examples

#include <iostream> // no semicolon after directive

using std::cout; // console output

using std::endl; // newline

extern int i; // Variable declaration without definition

extern float f(float); // Function declaration

float b; // Variable declaration & definition

float f(float a) // Function definition

{

  return a + 1.0;

}

int i; // Variable definition

int h(int x) // Function declaration & definition

{

  return x + 1;

}

int main()

{

  b = 1.0;

  i = 2;

  cout << f(b) << endl;

  cout << h(i) << endl;

  int i1, i2;

  // int i3, int i4; // compile error

  int i3; int i4; // OK

  // short sh, long l; // compile error

  short sh; long l; // OK

  return 0;

}

/*

g++ Declare.cpp -o Declare

./Declare

Declare

2

3

*/

Notes:  You can write std::cout and std::endl without any using statement. Alternatively, you can  use  the standard namespace with

using namespace std;

or use only what you need from the standard namespace, as in:

using std::cout;

using std::endl;

In both cases, you can then write cout and endl instead of std::cout and std::endl respectively.

If you use the entire standard namespace, then all the names in std become available, increasing the risk of name collision.

You can run the program with

./Declare

or

Declare

"." is the current directory. Both

program

and

./program

run the program "program" from the current directory.

You can compile the program without the -o (output) option,

g++ Declare.cpp

creating the file a.out, which you can run with

a.out

./a.out

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Hello.cpp     TCP1, p. 103          download

// Saying Hello with C++

#include <iostream> // Stream declarations

using std::cout;

using std::endl;

int main()

{

  cout << "Hello, world! I am "

       << 8 << " today!" << endl;

}

/*

g++ Hello.cpp -o Hello

./Hello

Hello, world! I am 8 today!

*/

Note:  Number 8 is printed as a string, so we could have written instead

<< "8 today!" << endl;

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Exercise 2-1     TCP1, p. 119     (Hello, world; family)

Exercise 2-1. Modify Hello.cpp so that it prints out your name and age (or shoe size, or your dog’s age, if that makes you feel better). Compile and run the program.

Family.cpp          download

#include <iostream> // Stream declarations

using std::cout; // console output

using std::endl; // newline

int main()

{

  cout << "Hello, world! My name is John Doe. I am "

       << 38 << " today!" << endl;

  cout << "My dog's name is Wolfy. He is 1 year old.\n";

}

/*

g++ Family.cpp -o Family

./Family

Hello, world! My name is John Doe. I am 38 today!

My dog's name is Wolfy. He is 1 year old.

*/

Note:  See also HeYou.cpp in Section ch2-Strings.

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Stream.cpp     TCP1, p. 105-106     (Print format - decimal, octal, hex)     download

#include <iostream>

using std::cout;

using std::endl; // newline

using std::dec; // decimal (base 10)

using std::oct; // octal (base 8)

using std::hex; // hexadecimal (base 16)

int main()

{

  // Specifying formats with manipulators:

  cout << "A number in decimal: "

       << dec << 15 << '\n';

  cout << "in octal: " << oct << 15 << "\n";

  cout << "in hex: " << hex << 15 << endl;

  cout << "A floating-point number: "

       << 3.14159 << char(10); // newline (ASCII 10)

  cout << "non-printing char (escape): "

       << char(27) << char(10); // newline

}

/*

g++ Stream.cpp -o Stream

./Stream

A number in decimal: 15

in octal: 17

in hex: f

A floating-point number: 3.14159

non-printing char (escape): 

*/

Note:  See the ASCII_code.

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Concat.cpp     TCP1, p. 106     (String concatenation)     download

// Character array (string) concatenation

#include <iostream>

int main()

{

  std::cout << "This is far too long to put on a "

    "single line, but it can be broken up with\n"

    "no ill effects as long as there is no "

    "punctuation separating adjacent\n"

    "character arrays.\n";

}

/*

g++ Concat.cpp -o Concat

./Concat

This is far too long to put on a single line, but it can be broken up with

no ill effects as long as there is no punctuation separating adjacent

character arrays.

*/

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Numconv.cpp    TCP1, p. 107     (Decimal to octal and hex)     download

// Converts decimal to octal and hex

#include <iostream>

using std::cout;

using std::cin;

using std::endl;

using std::oct;

using std::hex;

int main()

{

  int number;

  cout << "Enter a decimal number: ";

  cin >> number;

  cout << "value in octal = 0" << oct << number << endl;

  cout << "value in hex = 0x" << hex << number << endl;

}

/*

g++ Numconv.cpp -o Numconv

./Numconv

Enter a decimal number: 15

value in octal = 017

value in hex = 0xf

*/

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Exercise 2-2     TCP1, p. 120     (Circle)

Exercise 2-2. Using Stream.cpp and Numconv.cpp as guidelines, create a program that asks for the radius of a circle and prints the area of that circle. You can just use the ‘*’ operator to square the radius. Do not try to print out the value as octal or hex (these only work with integral types).

Circle.cpp          download

// prints the area of a circle, knowing the radius

#include <iostream>

using std::cout;

using std::cin;

using std::endl;

int main()

{

  float radius;

  cout << "Enter the radius: ";

  cin >> radius;

  cout << "Area: " << 3.14 * radius * radius << endl;

}

/*

g++ Circle.cpp -o Circle

./Circle

Enter the radius: 2.7

Area: 22.8906

*/

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CallHello.cpp     TCP1, p. 108     (system)     download

// Call another program

#include <cstdlib> // Declare "system()"

int main()

{

  system("Hello"); // program Hello must be in the same folder

}

/*

g++ CallHello.cpp -o CallHello

./CallHello

Hello, world! I am 8 today!

*/

Note:  See Hello.cpp above.

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