1 CS 192 Lecture 5 Winter 2003 December 10-11, 2003 Dr. Shafay Shamail

2 Constants Constants are specific values of any data type, such as ‘f’“hello” Character constants are enclosed in single quotes char ch = ‘z’; String constants are enclosed in double quotes string message = “Hello”;

3 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

4 #include int main() { char ch = ‘M’; //assign ASCII code for M to c int 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; }

5 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

6 Scope of Variables Local Global Block Function File Program Class ?

7 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

8 #include 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; }

9 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

10 #include int i = 2;//global void func() { cout << i << endl; int i = 3;//local cout << i << endl; } int main() { cout << i << endl; func(); cout << i << endl; int i = 5; cout << i << endl; return 0; }