Elements of C

Before moving into the depth of c programming language let's have a look at the different elements of c .

These elements are necessary for making the structure of a c program .

If you want to know more about c programming language then read this post "Introduction to C Programming Language - Introduction , Basic and History ".

Character Set in C :-

It  combines  small  alphabets,  capital  alphabets,  digits  and  special symbols to write a program.

·       a-z(ASCII code->97-122)

·       A-Z(ASCII code->65-90)

·       0-9(ASCII code->48-57)

·       Special  Symbols 

 Constants in c :-

Constants are the fixed quantity whose value can never be change throughout the program execution.

Types:-

1.    Integer constant-

-may be +ve or –ve.

-range is -32768 to +32767

-size is 2 bytes

-examples are 9,-346

2.    Float/real constant-

-may be +ve or _ve

-range is -3.4x10³⁸ to _3.4x10³⁸

-size is 4 bytes

-examples are 1/3,-4.89

3.    Character/string constant

-if it is a character constant then it must be enclosed within a pair of single quote and size is one byte. ex-‘s’(1 byte)

-if it is a string constant then it must be enclosed within a pair of double quote and size is not fixed. ex-“anil”(no range)

Q. As per constant definition a=2 then a can replace 2 and 2 can replace a in the program. The why we need a we can directly write 2 any where it will save 2 bytes of memory. 

Ans: Suppose we have create an application which take rate of interest while starting. 

Today return of investment (roi ) is 2% tomorrow it can be 3% if we write 2% directly into the program then we have change the code regularly  and compile it again & again.

Variables :-

These are the temporary named memory locations where the constant values are stored. 

Every constant value must be associated with a variable inside the memory.

Rules for constructing a variable:-

1.      variable name must starts with an alphabet or an underscore(_).

2.      It cannot starts with a digit.

3.      But digits can be placed after first place.

4.      No blank space is allowed while declaring a variable.

5.      Variable name length must not be more n 38 characters.

6.      No special symbols except underscore is allowed while declaring a variable.

Tokens :-

These  are  the  combinations  of  constants,  operators,  strings,  special symbols, keywords and identifiers.

Commenting Lines :-

These are used to deactivate line of code(s) which are present but not used inside the program.

Types:

1.      single line comment:-used to deactivate a single line using the symbol (//).

ex-//printf(“hello”);

2.      multiline comment:-used to deactivate more than one line at a time.(/* */)

ex-/* int a;

a=5;

printf(“%d”,a); */

Although comments are not necessary to use in a program but it increases the readibility of program and it also provided your program a professional look .

Identifiers:-

These are the user-defined words specially used for constructing variable, function or array. The length of identifiers must not be more than 31 characters.

Also , you cannot use some terms as identifier like c or microsoft as these terms are reserved for an special purpose . 

Identifiers in c are one of the most important thing.

Delimeters/literals:-

These are the special symbols which are used for specific purposes for the programming like * is used for pointer and & is used for address.

Keywords:-

These are also called as reserve words.

These are the pre-defined words which carry a special meaning for the compiler and we cannot change the name of these keywords. 

There are 32 keywords available in c language.

auto                        double                   int                     struct

break	else	long	switch
case	enum	register	typedef
char	extern	return	union
const	float	short	unsigned
continue	for	signed	void
default	goto	sizeof	volatile
do	if	static	while

Datatypes:-

 Datatypes  decides which type of dada a variable can take. 

It always used as a suffix for the variable. There are different types datatypes used in c programming language.

1. Primary datatype:- It is also called predefined/built-in/primitive datatype.

example:-

Datatype              Bytes                            RANGE                                    FS

short int	2	-32,768 to 32,767	%hd
unsigned short int	2	0 to 65,535	%hu
unsigned int	4	0 to 4,294,967,295	%u
int	4	-2,147,483,648 to 2,147,483,647	%d
long int	4	-2,147,483,648 to 2,147,483,647	%ld
unsigned long int	4	0 to 4,294,967,295	%lu
long long int	8	-(2^63) to (2^63)-1	%lld
unsigned long long int	8	0 to 18,446,744,073,709,551,615	%llu
signed char	1	-128 to 127	%c
unsigned char	1	0 to 255	%c
float	4		%f
double	8		%lf
long double	12		%Lf

2.      Secondary datatype:- It is categorized into two types.

i.                derived datatype:-

ex:-array, function, pointer

ii.               user-defined datatype:- ex-struct, union, enum

Pre-Processor directives :-

A pre-processor directive will always start with a special symbol (#) and is generally known as headerfile in the code .

It main usage is found in the process of  compilation it tells the compiler to do a specific task and finally on the basis of that compiler process the code .

If you want to know about best C or C++ compiler then read this post "Top Ide for C and C++ Developers - 2019 ".



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