lesson 3

1 Character set:
C++ has the letters and digits, as show below:
Uppercase: A, B, C, . . ., Z
Lowercase: a, b, c, . . ., z
Digits: 0, 1, 2, . . .,9
Special Characters: All characters other than listed treated as special characters for example:
“ (Double Conations) . (Dot) : (Colon) ; (Semicolon) (Blank Space)
In C++ language, upper case and lower case letters are distinct and hence there are 52 letters in all. For example bag is different from Bag which is different from BAG.
2 Identifiers:
An identifier is a name given to some program entity, such as variable, constant, array, function, structure, or class. An identifier is a sequence of alphanumeric (alphabetic and numeric) characters, the first of which must be a letter, and can’t contain spaces. The length of an identifier is machine dependent. C++ allows identifiers of up to 127 characters.
A variable should not begin with a digit. C++ does not set a maximum length for an identifier. Some examples of valid identifiers are as follows:
My_name (7 char.)
i (1 char.)
B (1 char.)
Examples of invalid identifiers are: 3ab a()test ros sal