Declarations in C programming

A declaration associates a group of variables with a specific data type. All variables must be declared before they can appear in executable statements. A declaration consists of a data type, followed by one or more variable names, ending with a semicolon. Each array variable must be followed by a pair of square brackets, containing a positive integer which specifies the size (i.e. the number of elements) of the array.

A C program contains the following type declarations:

int a, b, c ;

float root1, root2 ;

char flag, text [80],

Thus, a, b and c are declared to be integer variables, root1 and root 2 are floating variables, flag is a char-type variable and text is an 80-element, char-type array. Square brackets enclosing the size specification for text.

These declarations could also have been written as follows:

int a ;

int b ;

int c ;

float root1 ;

float root2 ;

char flag ;

char text [80] ;

# A C program contains the following type declarations:

short int a, b, c ;

long int r, s, t ;

int p, q ;

Also written as

short a, b, c ;

long r, s, t ;

int p, q ;

short and short int are equivalent, as are long and long int.

# A C program contains the following type declarations

float c1, c2, c3 ;

double root1, root2 ;

also written as

long float root1, root2 ;

# A C program contains the following type declarations.

int c = 12 ;

char star = ‘*’ ;

float sum = 0. ;

double factor = 0.21023e-6

Thus, c is an integer variable whose initial value is 12, star is a char type variable initially assigned the character ‘*’, sum is a floating point variable whose initial value is 0. , and factor is double precision variable whose initial value is 0.21023 × 106.

# A C program contains the following type declarations.

char text [ ] = “California” ;

This declaration will cause text to be an 11-element character array. The first 10 elements will represent the 10 characters within the word California, and the 11th element will represent the null character (\0) which automatically added at the end of the string.

Te declaration could also have been written

char text [11] = “California” ;

Where size of the array is explicitly specified. In such situations, it is important, however, that the size be specified correctly. If the size is too small, eg. ,

char text [10] = “California” ;

The character at the end of the string (in this case, the null character) will be lost. If the size is too large e.g.,

char text [20] = “California” ;

The extra array elements may be assigned zeros, or they may be filled with meaningless characters.

c    a    l    i     f     o     r    n     i    a   \0

The array is another kind of variable that is used extensively in C. An array is an identifier that refers to collection of data items that have the same name. The data items must all be of the same type (e.g. all integers, all characters). The individual data items are represented by their corresponding array element (i.e. the first data item is represented by the first array element, etc). The individual array elements distinguished from one another by the value that is assigned to a subscript.

Subscript: 0    1     2   3    4    5    6    7    8    9    10