One-dimensional arrays in C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a one-dimensional array in C?

A one-dimensional array in C is a collection of elements of the same type stored in contiguous memory locations. It is like a list where each element can be accessed by its index.

beginner

How do you declare a one-dimensional array of 5 integers in C?

You declare it like this: int arr[5]; This creates an array named arr that can hold 5 integers.

beginner

How do you access the third element of an array named arr?

You access it using the index 2: arr[2]. Remember, array indexes start at 0, so the first element is arr[0].

intermediate

What happens if you try to access an array element outside its declared size?

Accessing outside the array size causes undefined behavior. It may read or write memory it shouldn't, leading to bugs or crashes.

beginner

How can you initialize a one-dimensional array with values at the time of declaration?

You can write: int arr[3] = {10, 20, 30}; This sets the first element to 10, second to 20, and third to 30.

What is the index of the first element in a C array?

A 0

B 1

C -1

D Depends on the array size

In C, array indexing always starts at 0.

Which of the following declares an array of 10 floats?

A int arr[10];

B float arr[10];

C float arr;

D float arr(10);

The correct syntax for declaring an array of 10 floats is float arr[10];.

What will happen if you write to arr[5] when arr is declared as int arr[5];?

A It causes undefined behavior

B It writes to the last element safely

C It throws a compile-time error

D It automatically resizes the array

Accessing arr[5] is outside the bounds since valid indexes are 0 to 4, causing undefined behavior.

How do you initialize an array with all zeros in C?

A int arr[5] = NULL;

B int arr[5] = 0;

C int arr[5]; // automatically zeroed

D int arr[5] = {0};

Initializing with {0} sets the first element to zero and all others to zero by default.

Which statement correctly accesses the last element of int arr[7];?

A arr[-1]

B arr[7]

C arr[6]

D arr[0]

The last element index is size minus one, so for 7 elements, it is arr[6].

Explain what a one-dimensional array is and how you use it in C.

Think of it like a row of boxes where each box holds a value.

Describe how to declare, initialize, and access elements in a one-dimensional array in C.

Remember the array size and zero-based indexing.