LESSON FOUR

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:
+ - * / ^
( [ { } ]
) < = > , (comma)
“ (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.)
lesson three lecture 3
examples of invalid identifiers are:
3ab a()test ros sal
3 keywords:
the keywords are also identifiers but cannot be user defined, since they
are reserved words. all the keywords should be in lower case letters. reserved
words cannot be used as variable names or constant. the following words are
reserved for use as keywords:
some of c++ language reserved words:
break case char cin cout
deleting double else enum false
float for goto if int
long main private public short
sizeof switch true union void
4 constants:
there are three types of constants: string constants, numeric constants,
and character constants.
1. string constants: a string constants are a sequence of alphanumeric
characters enclosed in double quotation marks whose maximum length is 255
characters. in the following are examples of valid string constants: (“the
result=”, “rs 2000.00”, “this is test program”). the invalid string constants are
like: (race, “my name, ‘this’).
2. numeric constants: numeric constants are positive or negative numbers.
there are four types of numeric constants: integer, floating point,
hexadecimal, and octal.
lesson three
(a) integer constants: do not contain decimal points: int x,y shortint x,y
longint x,y
? integer data: size (16 or 32) fill in -215 to 215-1 for 16 bit and -231 to
231-1 for 32 bit.
? short integer: fill in -215 to 215-1.
? long integer: fill in -231 to 231-1.
? unsigned: fill in (0 to 65635) for 16 bit and (0 to 4,294, 967, 295) for
32 bit.
(b) floating point constants: positive or negative numbers are represented
in exponential form. the floating point constant consists of an optionally
(signed) integer or fixed point number (the mantissa) followed by the
letter e and e and an optionally signed integer (the exponent). ex.
(9010e10, 77.11e-11).
? float 4 bytes.
? double 8 bytes.
? long double 12 or 16.
(c) hexadecimal constants: hexadecimal numbers are integer numbers of
base 16 and their digits are 0 to 9 and a to f.
integer integer
short integer (short)
long integer (long)
float single precision (float)
double precision (double)
long double
hexa short hexadecimal
long hexadecimal
unsigned
unsigned char
unsigned integer
unsigned short integer
unsigned long integer
octal short octal
long octal
lesson three
(d) octal constants: octal numbers are numbers of base 8 and their digits
are 0 to 7.