C Array

It is very difficult to define multiple variable names when using more data. So we can create an array to solve this difficulty (single variable name and more data).

• If the index of the array exceeds its size, the program may crash. Modern compilers usually handle such errors.
• We cannot initialize the size of an array dynamically. A constant expression is required.

Here we will learn about C Arrays.

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Array Rules

1. Arrays can store only the same data type.
2. Arrays are always passed by reference.
3. Array list should end with a semicolon ;. Otherwise, it will show an error.

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Base Address of Array

Example:

int a[10] = {0,1,2,3,4,5,6,7,8,9};

• The starting address of the array is called the base address.
• If the array starts at address 101, then a[0] is at 101.
• When we pass an array to a function, the base address is passed.

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Array Types

1. One Dimensional Array
2. Two Dimensional Array
3. Multi Dimensional Array

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One Dimensional Array

• When an array has one index, it is called a one-dimensional array.

Syntax

data_type array_name[size];

• data_type – Type of array elements
• array_name – Name of the array
• size – Number of elements

Example Declarations

int a[100];       // int (2Byte), size 100, memory 200 bytes
float s[50];      // float (4Byte), size 50, memory 200 bytes
char name[15];    // char (1Byte), size 15, memory 15 bytes

Reading and Writing

// Reading
for(i = 0; i < 100; i++)
    scanf("%d", &a[i]);

// Writing
for(i = 0; i < 100; i++)
    printf("%d", a[i]);

Array Initialization

data_type array_name[size] = {list_of_values};

Examples

static int age[3] = {10, 20, 30};     // age[0]=10; age[1]=20; age[2]=30
static float salary[] = {1000, 2200, 3300};
static char a[10] = "ArunEworld";     // a[0]='A'; a[1]='r'; ... a[9]='d';

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Array Initialization with Zero

• Partially initialized automatic arrays: remaining elements are set to 0.

Example 1

#include <stdio.h>
int main() {
    int awe[2];
    printf("%d, %d, %d, %d, %d, %d, %d, %d\n",
           awe[0], awe[1], awe[2], awe[3], awe[4], awe[5], awe[6], awe[7]);
    return 0;
}

/* Output: 0, 0, 0, 0, -467742907, 32525, 0, 0 */

Example 2

#include <stdio.h>
int main() {
    int awe[3] = {1, 2, 3};
    printf("%d, %d, %d, %d, %d, %d, %d, %d\n",
           awe[0], awe[1], awe[2], awe[3], awe[4], awe[5], awe[6], awe[7]);
    return 0;
}

/* Output: 1, 2, 3, 0, 0, -2036674747, 32587, 0 */

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Accessing Array Elements

#include <stdio.h>
int main() {
    int arr_aew[2] = {10, 2};
    printf("%d\n", 1[arr_aew]);  // Output: 2
    return 0;
}

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Two Dimensional Array

• An array with two indices.
• We can consider it as a table (rows and columns).

Syntax

data_type array_name[size_1][size_2];

• size_1 – number of rows
• size_2 – number of columns

Declaration Example

int a[100][20];   // int (2Byte), 100 rows, 20 columns

Reading and Writing

// Reading
for(i = 0; i < 10; i++)
    for(j = 0; j < 15; j++)
        scanf("%d", &a[i][j]);

// Writing
for(i = 0; i < 10; i++)
    for(j = 0; j < 15; j++)
        printf("%d", a[i][j]);

Array Initialization

data_type array_name[size_1][size_2] = {v1, v2, ..., vn};

Examples

static int mark[3][2] = {60, 70, 80, 35, 90, 18};
// mark[0][0]=60; mark[0][1]=70; mark[1][0]=35; mark[1][1]=90; mark[2][0]=18;

static int mark2[3][2] = {{50}, {0}, {35}};
// mark2[0][0]=50; mark2[0][1]=0; mark2[1][0]=0; mark2[1][1]=0; mark2[2][0]=35; mark2[2][1]=0;

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Multi Dimensional Array

• Arrays with 3 or more dimensions.
• Maximum dimension depends on compiler.

Syntax

data_type array_name[size_1][size_2]...[size_n];

Example

int a[10][10][10];  // int (2Byte), 10x10x10 elements, memory 2000 bytes

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Array Disadvantages

1. Arrays are static, cannot easily expand or shrink.
2. Inserting or deleting elements is expensive.

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Exercises

1. Find the Number of Elements in an Array

Method 1 (Known Data Type)

#include <stdio.h>
int main() {
    int array[] = {15, 50, 34, 20, 10, 79, 100};
    int n = sizeof(array) / sizeof(int);
    printf("Number of elements: %d\n", n);
    return 0;
}

Method 2 (Unknown Data Type)

#include <stdio.h>
int main() {
    int size, i;
    int Arr[5] = {88, 97, 65, 43, 77};
    size = 5;
   
    printf("\nBefore Array value:\t");
    for(i = 0; i < size; i++)
        printf("%d\t", Arr[i]);
    
    getchar();
    return 0;
}

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2. Sum of 10 Elements in an Array

#include <stdio.h>
#include <conio.h>

int main() {
    int num_array[10], i, sum = 0;
    int *ptr;

    printf("\nEnter 10 Elements:\n");
    for(i = 0; i < 10; i++)
        scanf("%d", &num_array[i]);

    ptr = num_array;

    for(i = 0; i < 10; i++) {
        sum = sum + *ptr;
        ptr++;
    }

    printf("\nSum of the array's 10 elements: %d", sum);
    return 0;
}

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