C Mistakes – 1d array

Array is one of the important concept in c programming, while learning or practicing array most of the beginners unknowingly follow incorrect or invalid syntax of array.

Mistake 1 .Constant Expression Require

#include<stdio.h>
void main()
{
int i=10;
int a[i];
}

Consider the above example,

1. We are going to declare an array whose size is equal to the value of variable.
2. If we changed the value of variable then array size is going to change.
3. According to array concept, we are allocating memory for array at compile time so if the size of array is going to vary then how it is possible to allocate memory to an array.

Value of Const Variable Cannot be changed :

we know that value of Const Variable cannot be changed once initialized so we can write above example as as below -

#include<stdio.h>
void main()
{
const int i=10;
int a[i];
}

or

int a[10];

Recommanded Article : Compile Time Initializing an Array

Mistake 2 .Empty Valued

#include<stdio.h>
void main()
{
int arr[];
}

Consider the above example, we can see the empty pair of square brackets means we haven’t specified size of an array. In the example array ‘arr’ is undefined or empty.

#include<stdio.h>
void main()
{
int a[] = {1,1};
}

above syntax will take default array size equal to 2. [Refer Article : Section B]

#include<stdio.h>
void main()
{
int a[] = {}; // This also Cause an Error
}

Mistake 3 .Does Not Checks Bound Checking

#include<stdio.h>
void main()
{
int a[5];
printf("%d",a[7]);
}

1. Here Array size specified is 5.
2. So we have Access to Following Array Elements - a[0],a[1],a[2],a[3] and a[4]
3. But accessing a[5] causes Garbage Value to be used because C Does not performs Array Bound Check.

If the maximum size of array is “MAX” then we can access following elements of an array -

Elements accessible for Array Size "MAX" = arr[0]
                                         = .
                                         = .
                                         = .
                                         = arr[MAX-1]

Mistake 4 .Case Sensitive

#include<stdio.h>
void main()
{
int a[5];
printf("%d",A[2]);
}

Array Variable is Case Sensitive so A[2] does not print anything it Displays Error Message : “Undefined Symbol A”

Some Important Array Tips :

Tip 1 : Use #define to Specify Array Size

#include<stdio.h>
#define MAX 5
void main()
{
int a[MAX];
printf("%d",a[2]);
}

• As MAX is replaced by 5 for every Occurrence , So In due Course of time if you want to increase or decrease Size of array then change should be made in

#define MAX 10

Tip 2 : a[i] and i[a] are Same

Visit this article which will explain how to access array randomly using a[i] and i[a].