1 cs 192 lecture 5 winter 2003 december 10-11, 2003 dr. shafay shamail

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CS 192

Lecture 5

Winter 2003

December 10-11, 2003

Dr. Shafay Shamail

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Constants

• Constants are specific values of any data type, such as

2 3.145 -2.3 ‘f’ “hello”

• Character constants are enclosed in single quoteschar ch = ‘z’;

• String constants are enclosed in double quotes

string message = “Hello”;

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Types of Constants

Character constants char c = ‘z’

Numeric constants int a = 10;

Hexadecimal constants int hex = 0xFF;

Octal constants int oct = 011;

String constants char greetings = “Hello”;

Backslash constants \b, \f, \n, \r, \t, \”, \’, \0, \\,

\v, \a, \?, \OCTAL, \xHEX

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#include <iostream.h>

int main(){

char ch = ‘M’; //assign ASCII code for M to cint number = ch; //store same code in an int

cout << “The ASCII code for “ << ch << “ is ” << in << ‘\n’;

cout << “Add one to the character code\n”;ch = ch + 1;in = ch;cout << “The ASCII code for “ << ch << “ is “

<< in << endl;

return 0;}

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Variables

• Needed to store information• Program must remember three properties: where,

what value, what kind int age; age = 40; double radius = 0.0;

• Have to be declared first; why?• Uninitialized variables have garbage values• C++ is case-sensitive

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Scope of Variables

• Local• Global

• Block• Function• File• Program

• Class ?

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Local Variables• Declared inside a function

• Die when function finishes; unknown outside their function

• Initialized each time the function containing them is entered; uninitialized have garbage values

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#include <iostream.h>

void func(){ int x; // local to func()

x = -199; cout << x; // displays ?}

int main(){ int x; // local to main() x = 10;

func();

cout << "\n"; cout << x; // displays ?

return 0;}

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Global Variables

• Declared outside any function; have life as long as the program runs

• Can be used by all following functions• Usually placed at the beginning of program• Initialized only at the start of the program;

uninitialized default to zero• An identically named local variable masks global one• Should be avoided if possible

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#include <iostream.h>

int i = 2; //global

void func(){

cout << i << endl;int i = 3; //localcout << i << endl;

}

int main(){

cout << i << endl;

func();

cout << i << endl;

int i = 5;cout << i << endl;

return 0;}