Array in c

Array tutorials in c programming language by examples

An array is derived data type in c programming language which

can store similar type of data in continuous memory location.

Data may be primitive type (int, char, float, double…), address of

union, structure, pointer, function or another array.

Example of array declaration:

int arr[5];
char arr[5];
float arr[5];
long double arr[5];
char * arr[5];
int (arr[])();
double ** arr[5];

Array is useful when:

(a) We have to store large number of data of similar type. If we

have large number of similar kind of variable then it is very

difficult to remember name of all variables and write the

program. For example:

//PROCESS ONE
#include<stdio.h>
int main(){
    int ax=1;
    int b=2;
    int cg=5;
    int dff=7;
    int am=8;
    int raja=0;
    int rani=11;
    int xxx=5;
    int yyy=90;
    int p;
    int q;
    int r;
    int avg;
    avg=(ax+b+cg+dff+am+raja+rani+xxx+yyy+p+q+r)/12;
    printf("%d",avg);

    return 0;      
}
If we will use array then above program can be written as:

//PROCESS TWO
#include<stdio.h>
int main(){
    int arr[]={1,2,5,7,8,0,11,5,50};
    int i,avg;
    for(int i=0;i<12;i++){
         avg=avg+arr[i];
    }
    printf("%d",avg/12);
    return 0;      
}

Question: Write a C program to find out average of 200 integer

number using process one and two.

(b) We want to store large number of data in continuous memory

location. Array always stores data in continuous memory location.

(q) What will be output when you will execute the following

program?

#include<stdio.h>
int main(){
int arr[]={0,10,20,30,40};
    char *ptr=arr;
    arr=arr+2;
    printf("%d",*arr);
    return 0;      
}

Advantage of using array:

1. An array provides singe name .So it easy to remember the

name of all element of an array.

2. Array name gives base address of an array .So with the help

increment operator we can visit one by one all the element of an

array.

3. Array has many application data structure.

Array of pointers in c:

        Array whose content is address of another variable is known

as array pointers.  For example:

#include<stdio.h>
int main(){
float a=0.0f,b=1.0f,c=2.0f;
    float * arr[]={&a,&b,&c};
    b=a+c;
    printf("%f",arr[1]);
    return 0;      
}

Complex arrays in c

1. Declaration of an array of size five which can store address

such functions whose parameter is void data type and return type

is also void data type:


void ( arr[5] )( );

2. Declaration of an array of size five which can store address

such function which has two parameter of int data type and

return type is  float data type:

float ( arr[5] )(int, int);

3. Declaration of an array of size two which can store the address

of printf or sacanf function:

int ( arr[2] )( const char *, … );

Note: prototype of printf function is:  int printf( const char *, … );

Different type of array in c:

(a) Array of integer
    An array which can hold integer data type is known as array of

integer.

(b) Array of character
    An array which can hold character data type is known as array

of character.

(c) Array of union
    An array which can hold address of union data type is known as

union of integer.

For example:

(1) What will be output when you will execute the following

program?

#include<stdio.h>
union A{
char p;
float const * const q;
};
int main(){
    union A arr[10];
    printf("%d",sizeof arr);
   return 0;    
}

Output: 20

(2) What will be output when you will execute the following

program?

#include<stdio.h>
union A{
    char character;
    int ascii;
};
int main(){
    union A arr[2]={{65},{'a'}};
    printf("%c %c",arr[0],arr[1]);
       return 0;    
}

Output: A a

(d) Array of structure
 An array which can hold address of structure data type is known

as array of structure. For example:

(1) What will be output when you will execute the following

program?

#include<stdio.h>
typedef struct stu{
    char * name;
    int roll;
}s;
int main(){
    s arr[2]={{"raja",10},{"rani",11}};
    printf("%s %d",arr[0]);
    return 0;      
}

Output: raja 10

(2) What will be output when you will execute the following

program?

#include<stdio.h>
struct A{
    int p;
    float q;
    long double *r;
};
int main(){
    struct A arr[10];
    printf("%d",sizeof arr);
 
    return 0;      
}

Output: 80

(e) Array of string
    An array which can hold integer data type is known as array of

integer.

(f) Array of array
    An array which can hold address of another array is known as

array of array.

(g) Array of address of integer
    An array which can hold address integer data type is known as

array of address of integer.

Pointer to array

A pointer which holds base address of an array or address of any

element of an array is known as pointer to array. For example:

(a)

#include<stdio.h>
int main(){
    int arr[5]={100,200,300};
    int *ptr1=arr;
    char *ptr2=(char *)arr;
    printf("%d   %d",*(ptr1+2),*(ptr2+4));

       return 0;    
}
Output: 300   44

(b)

#include<stdio.h>
int main(){
    static int a=11,b=22,c=33;
    int * arr[5]={&a,&b,&c};
    int const * const *ptr=&arr[1];
    --ptr;
    printf("%d ",**ptr);
        return 0;      
}

Output: 11