CS 1400

Pick ups from chapters 2 and 3

#include directive

• This pre-processing directive causes the textual contents of a named file to be inserted into a program file at this point.

• Include files typically contain information necessary to use externally-defined utilities (such as I/O, math, etc.)

Character variables

• A variable of type char can hold one character;

char sex;

• A character constant is delimited by single quotes;

sex = ‘f’;

if (sex == ‘m’)

cout << “male”;

char vs. literals

• A literal is different from a character! char c;

cout << “hello world”;

c = “hello world”; // ERROR!

c = ‘h’; // CORRECT

c = “h”; // ERROR!

variable types (Visual C++)

type Size Rangebool 1 byte true or false

char 1 byte any single character

short 2 bytes -32,768 to 32,767

unsigned short 2 bytes 0 to 65,535

int 4 bytes -2,147,483,648 to 2,147,483,647

unsigned int 4 bytes 0 to 4,294,967,295

long 4 bytes same as int

unsigned long 4 bytes same as unsigned int

float 4 bytes +/- 3.4E-38 to +/- 3.4E38

double 8 bytes +/- 1.7E-308 to +/- 1.7E308

*FYI

Determining the size of variables

• The library function sizeof() can be used to determine the size of variables or types on other systems:

cout << sizeof (float);

*FYI

Constants

• C++ allows the programmer to control the type and base of a constantcout << 32; // defaults to int

cout << 32L; // becomes long

cout << 3.14; // defaults to double

cout << 3.14F; // becomes float

cout << 032; // becomes base-8 or 26

cout << 3.14e-3; // becomes .00314

*FYI

Named constants

• Constants may be given symbolic names to represent them in a program;– Form: const type name = value;– Example:

const float PI = 3.14159;

const int SIZE = 24;

– Alternative Form:#define name value#define PI 3.14159

#define SIZE 24

Defines should be place above main()

cin I/O rules

• Only digit characters (and sign) can be entered for an int variable.

• Only digit, decimal, and possibly E-notation characters (and sign) can be entered for a float variable.

• Only printable characters can be entered for a char variable.

Strings or char arrays

• A message or string of characters can be stored in a special array variable; char word[80]; // holds <80 characters

cin >> word;

cout << word << endl;

• Only printable characters can be input using cin (no blanks, tabs, etc.)

Initially limit use of string arrays…

• For now, only input and output will be done on arrays;

cin >> word; // OK

cout << word; // OK

word = “hello world”; // ERROR!

if (word < “goodbye”) // ERROR!

word1 = word2; // ERROR!

Combining assignments

• Multiple assignment statements may be combined– Example:

a = b = c = 25;

• Shorthand notation for combining arithmetic operations and assignment– Example:

a = a * 2; same as a *= 2;b = b – 5; same as b -= 5;c = c / 7; same as c /= 7;

Additional shorthand notation…

• incrementing a variablevalue++ same as value = value + 1

• decrementing a variablevalue-- same as value = value - 1

Formatting output

• Requires: #include <iomanip>• cout manipulators:

setw(n)• (set the minimum spaces for the next value output)

setprecision(n)• (set the precision or rounding for a float value)

fixed• (force output of float values in fixed-point notation)

showpoint• (show a decimal point with trailing zeros)

Controlling input

• Requires #include <iomanip>• cin manipulators

setw(n)• do not input more than n-1 characters for the next

variable

textbook error, pg 128

char word[5];

cin >> setw(5) >> word; // user enters “Eureka”

cout << word; // program outputs “Eure”

Special input examples…char sentence[20], ch;

cin.getline(sentence, 20);– reads all characters on a line (up to 19 in count) from

the keyboard and stores them in array sentencecin.get(ch);

– reads the next input character (including white spaces)

cin >> ch;– reads the next printable character (ignoring white

spaces)cin.ignore ();

– ignore (discard) the next input buffer character

More math library functions…More math library functions…

Requires: #include <cmath>functions examples

abs y = abs(x);

sqrt y = sqrt(a*a + b*b);

log y = log(x);

sin y = sin(x+z);

cos y = cos(x);

tan y = tan(x);etc…

File OutputRequires: #include <fstream>

ofstream fout;fout.open (“report.txt”);fout << “hello from a file!\n”;fout.close();

To write to report.txt on the a: drive;fout.open (“a:\\report.txt”);fout.open (“a:report.txt”);fout.open (“a:\report.txt”); // ERROR!

File Input

Requires: #include <fstream>

int a, b;

ifstream fin;

fin.open (“report.txt”);

fin >> a >> b;

cout << “sum is: “ << a+b << endl;

fin.close();

Example…

• Write a program to generate a monthly report of concert hall business for a touring show. Up to 20 concerts are given.– assume: reserved seat tickets $80

stadium seat tickets $50

standing tickets $35

production company gets 80%

Input file…

line 1: tour name

line 2: reserved stadium standing

line 3: …

line n: -1 -1 -1

Example: Rolling Stones Geriatric Tour

3025 7500 4110

3026 7320 4098

3027 6432 2456

-1 -1 -1

a:tour.txt