C programming arrays

In this tutorial, you will learn about c programming arrays.

Arrays in C programming

An array is a collection of same types of data items that are placed in the contiguous memory location on computers memory.

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When we need to handle the multiple data of similar types arrays are used.

For example, we need 10 unique variables for 10 data items of integer type which make program bulky and tedious but with an array, we can create a single pack of 10 integer data items.

For example:

int num[10];     //num is a variable that will hold 10 integer data items

Basically, there are two types of arrays:

• One dimensional array
• Multidimensional array

Syntax of one-dimensional array

data_type variable_name[array_size];  //declaring an one dimensional 

In above syntax, the “data_type” as the name suggests defines the types of data items that the array will be holding,“variable_name” defines the unique name of an array and the “array_size” defines the number of elements contained in the array.

Array and Memory

Once the array is declared it must be initialized otherwise it will contain a garbage value.

General form of initialization an array

data_type variable_name[size] = { list };  //initializing an array

The values in the list are separated by commas.

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For example:

int a[]={1,2,3,4,5};

This declaration will create an array like this:

Or if we insert size of an array then the number of elements must not exceed the size.

int a[5]={0};  //this will assign 0 to all 5 elements

To initialize character arrays

char a[]={'a','b','c','d'};

Normally, when we declare multiple variables they occupy memory and are randomly placed in computers memory heap, however, when we declare an array of multiple data items these items occupy the continuous memory locations in computers memory heap.

For example, take an integral constant which takes 4 bytes of computers memory.

Now, if the first element of an array a[0] is stored at memory location 0x12 (say) then the second element a[1] of an array will be stored at the memory location adjacent to it which is 0x16 as integer occupies 4 bytes of memory.

Initializing an array with a symbolic constant

#include <stdio.h>
#define SIZE 5    //sizi of array
int main()
{ 
  int a[SIZE] = {1,2,3,4,5};    //array a has SIZE elements
  ....
}

Here, #define preprocessor directive defines a symbolic constant SIZE whose value is 5.

Array example: C program to print sum of first 5 numbers entered by the user

#include <stdio.h>
#include <stdio.h>
int main ()
{
 int i, a[5] ,sum = 0;  //a[5] is array that can hold 5 integer data items
 for(i=0;i<5;i++)  //loop to be repeated 5 times
  {
   printf("enter the number "<< i+1<<":");
   scanf("%d", &a[i];
   sum = sum + a[i];
  }
 printf("sum = %d",sum);
 return 0;
}  //end of program

Output

enter the number 1 : 1
enter the number 2 : 2
enter the number 3 : 3
enter the number 4 : 4
enter the number 5 : 5
sum = 15

Summary

• An array is similar to the variable except that it can store multiple elements of similar data type.
• Array elements are stored in contiguous memory locations and can be accessed using pointers.
• Array variable acts as a pointer to the zeroth element of the array.
• When the pointer is increased it points to next location of its type.