Basic Elements of C Language

2 | Basic Elements of C Language

2.0 | Contents :

     1.   Characters
     2.   Keywords
     3.   Identifiers
     4.   Constants
     5.   Data Types
     6.   Escape Sequences

2.1 | Characters :

Characters used in C language are classified into four types :

Letters
Digits
Special Characters
White Spaces

Characters	Elements
Letters	Uppercase A - Z Lowercase a - z
Digits	0 to 9
Special Characters	, comma	; semicolon
	? question mark	$ dollar symbol
	# number sign	~ tild
	* asterisk	+ plus
	- minus	% percentage
	< less than	> greater than
	! exclamation mark
White Spaces	Blank Space	New Line
	Form Feed	Horizontal Tab
	Carriage Return

2.2 | Keywords :

Keywords are standard predefined words to use in C language. The user/programmer can't change its meaning. Keywords are always written in the lower case. Keywords given below are used in C language :

Keywords of C Language
switch	for	char	default
while	include	nested	int
boolean	case	sizeof	do
double	void	const	break
continue	go to	for	if
else	float	long	char
auto	static	signed	volatile
register	union	short	struct

2.3 | Identifiers :

Names of variables, functions or arrays are called as identifiers. Identifiers are defined by user (for eg.: int a ; here, a is the name of variable of integer data-type defind/written by user/programmer).

Rules for naming of identifiers :

Identifiers are formed with alphabates, digits and only one special character i.e. underscore ( _ ).
The first character of an identifier must be an alphabate no matter it is in uppercase or in lowercase.
No special characters are usable for identifiers except underscore.
White spaces aren't allowed in between the naming of identifiers.
Identifiers are case sensitive (i.e. main is different from MAIN).

Valid Identifiers	Invalid Identifiers
app12	12app
app_11	app _ 11
App32	App 32

2.4 | Constants :

A constant is a quantity whose value does not change during the execution of C program. There are three types of constants in C language :

Numeric Constants
Character Constants
String Constants

1. Numeric Constants :
This constant is made up of digits. There are two types of numeric constant :

Integer or Fixed Point Constants :
It is made up of only integer digits i.e there is no decimal point in integer or fixed point constants. Its range is from -32,768 to 32,767. For eg.: -121, 546, etc.
Real or Floating Point Constants :
It consist of any number with one decimal point. For eg.: 54.746

2. Character Constants :
This type of constants are used to represent an alphabet. Alphabet used for character constant is written in single quotes. For eg.: 'A', 'b', etc.

3. String Constants :
This type of constants are used to represent a word (i.e. set of characters) in double quotes. For eg.: "Study", "language", etc.

2.5 | Data Types :

Data-types are used to store various types of data that is processed by the program. Data-type is used with the name of variables, functions or arrays to define there data-types. Data-types used in C language are given below :

Data Type	Type of Variable	Size (in bytes)	Range
char	Character	1	-128 to 127
unsigned char	Unsigned Character	1	0 to 255
int	Integer	2	-32,768 to 32,767
short / short int	Short Integer	1	-32,768 to 32,767
long	Long Integer	4	-2,14,74,83,648 to 2,14,74,83,648
unsigned int	Unsigned Integer	2	0 to 65,535
unsigned short	Unsigned Short Integer	2	0 to 65,535
unsigned long	Unsigned Long Integer	4	0 to 4,29,49,67,295
float	Floating Point Digits	4	3.4e-38 to 3.4e+38
double	Floating Point Digits	8	1.7e-308 to 1.7e+308

Note :
Characters, keywords, identifiers, constants and data-types these all are integral parts of variables in C language. So we read the topic variable in next lesson seperately.

2.6 | Escape Sequences :

Escape Sequences	Meaning
\\	\ character
\'	' character
\"	" character
\?	? character
\a	alert OR bell
\b	backscape
\f	form feed
\n	new line
\r	carriage return
\t	horizontal tab
\v	vertical tab
\ooo	octal number of one to three digits

C Programming Language

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