Variables and Data Types

 Variable: Portion of memory for storing a determined value.  Could be numerical, could be character or sequence of characters called strings  Variable examples: 20, “California”, ‘a’ etc…

 Valid Identifier: Used to identify a particular variable in the memory. Like a reference.  Sequence of one or more letters, digits or one underscore character.  Cannot start with number  Best practice is to start with a letter.  Examples: myValue, _num, num2 etc…

 Cannot use words like: asm, auto, bool, break, case, catch, char, class, const, const_cast, continue, default, delete, do, double, dynamic_cast, else, enum, explicit, export, extern, false, float, for, friend, goto, if, inline, int, long, mutable, namespace, new, operator, private, protected, public, register, reinterpret_cast, return, short, signed, sizeof, static, static_cast, struct, switch, template, this, throw, true, try, typedef, typeid, typename, union, unsigned, using, virtual, void, volatile, wchar_t, while  Or, cannot use and, and_eq, bitand, bitor, compl, not, not_eq, or, or_eq, xor, xor_eq

 C++ is case sensative  Name identifier like abc is not same as Abc or ABC. They are identified completely differently

 Computer needs to know what kind of data we are storing in case we will have to process those data later on for other purposes.  Fundamental data types:  char : Character or small integer, size=1 byte  short int(short) : short integer, size: 2 bytes  int: Integer, size: 4bytes  long int(long): long integer 4bytes  bool: Boolean value(true or false, 1 or 0), size: 1byte  float: decimal number, size: 4 bytes  double: double precision floating point number, size: 8 bytes  long double: size: 8bytes  wchat_t : Wide character, size: 2 or 4 bytes

 int a;  identifier is a, data type is integer  float b;  identifier is b, data type is b;  double num;  identifier is num, data type is double  int a, b, c;  3 integer variables named a, b, c  Same as int a;  int b;  int c;

 Signed: can have both positive and negative numbers  Unsigned: Only positive numbers  Example: signed int a; unsigned int b;  Default is signed in c++ so if nothing is given it takes it as signed. Example int a; is signed integer a.

#include using namespace std; int main() { int a, b; int sum; a=23; b=56; sum=a+b; cout << sum; return 0; }

 Variable needs to be declare first to be initialized.  int a;  is declaring variable, saying that make a new variable named a which is an integer  a = 23;  Initializing variable a and giving value 23 to a;  In c++ both can happen in same line  Example int a = 23;  First initialized int a( = 23;)  Then initialized int ( a = 23; )

 Can be initialized in two ways:  int a = 23;  Or  int a(23);

#include using namespace std; int main() { int a = 23; int b(56); int sum; sum=a+b; cout << sum; return 0; }

 Need to add #include to start the program  String: sequence of characters  Declaring string same as other variables except changing data type to string  Example: string myname;  Value of string data type always needs to be inside “ ”.  Example myname = “Dean”;  While declaring characters they should be given inside single quotes:  Example: char myChar=‘a’;  Character takes only one character while string is collection of character in one variable identifier

#include using namespace std; int main() { string MyName = “My name is Dean”; cout << MyName << endl; string AnotherString = “Jones”; string AddedString = MyName+AnotherString; cout << AddedString << endl; } Important!!! String Concatination (Adding two strings)

 Next Video: Constants  Then: Operators  Following with: Basic input and output to end the basics!!!