QUESTION 03 · Array Basics

What values are stored by int a[5] = {2, 4};?

2 marks

Answer

The values are 2, 4, 0, 0 and 0.

The explicit initialisers fill the first two elements.
The remaining elements are zero-initialised.

Explain array declaration and initialisation with examples.

5 marks

Answer in brief

An array declaration specifies its element type, name and size. Initialisation supplies starting values when the object is created.

Syntax and examples

int marks[4];
int scores[4] = {60, 70, 80, 90};
int values[] = {2, 4, 6};
int zeroes[4] = {0};

Meaning

marks has space for four integers. An ordinary automatic marks array without an initialiser does not have useful guaranteed starting values. scores receives all four listed values. The length of values is inferred as three from its initialisers. In zeroes, the first element is explicitly zero and the remaining elements are also zero-initialised.

Partial initialisation

int a[5] = {2, 4}; stores 2 and 4 in the first two positions and zero in the rest. Do not confuse this with int a[5]; at block scope, which does not initialise the ordinary automatic elements. Objects with static storage duration have their own default initialisation rules.

Assignment after declaration

Assign individual elements using a valid index, such as a[2] = 9;. Ordinary C arrays cannot be assigned as a whole using a = b. To copy elements between separate arrays, use a suitable loop or an appropriate library operation with correct bounds.

Size and complexity

Where the actual array declaration is visible, sizeof a / sizeof a[0] gives its element count for this ordinary array. It does not work as an array-length calculation on an adjusted array parameter. Initialising or copying n elements involves O(n) element work; one element assignment is O(1).

C program and output

Download .c Open compiler

/* CodeBhavya | PPS AR25 | Learning example */
#include <stdio.h>

int main(void)
{
    int a[5] = {2, 4};
    for (int i = 0; i < 5; ++i) { printf("%d\n", a[i]); }
    return 0;
}

Sample input and output

This example uses values already written in the program.

Output