Computer Science Chapter 5: Arrays

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Questions and Answers

What does the logical size of an array represent?

The total number of occupied slots within the array (correct)

The total number of elements in the defined array space

The maximum size the array can grow to

The number of memory slots allocated to the array

In the context of arrays, what is the meaning of the expression Abc[i+2]?

The sum of the two elements at index i and index 2

The 2nd element of the array Abc

The ith element plus two positions ahead in the array (correct)

The first element of the array Abc

What does the statement A[i] = 5; accomplish in C language?

It assigns the value 5 to the variable A

It assigns the value 5 to the ith position of array A (correct)

It allocates memory for the ith element

It outputs the value of 5 into the array A

If an array has a physical size of 100, what is a possible value for its logical size?

80 Signup and view all the answers

Which of the following statements is correct regarding array elements?

An array element can be treated like a single variable Signup and view all the answers

What is the primary reason for using an array instead of multiple variables to store student marks?

An array allows for easier data management and access. Signup and view all the answers

How is a one-dimensional array defined in an algorithm?

Array [1..N] of DataType. Signup and view all the answers

Which of the following statements about arrays is true?

An array holds a fixed-size collection of elements of the same type. Signup and view all the answers

In C programming, how is a one-dimensional array declared?

DataType ArrayName[Size]; Signup and view all the answers

What is the typical index range for a one-dimensional array declared with 100 elements?

0 to 99 Signup and view all the answers

What distinguishes a two-dimensional array from a one-dimensional array?

A two-dimensional array uses two indices to access its elements. Signup and view all the answers

Which of the following is a characteristic of arrays?

They must have a constant size at compile time. Signup and view all the answers

How is a two-dimensional array conceptually similar to a mathematical structure?

It corresponds to a matrix. Signup and view all the answers

What is the correct way to declare an array of four floats named 'Mark' in C?

float Mark; Signup and view all the answers

When an array is initialized without specifying the size, how does the compiler determine the size?

It counts the number of elements provided in the initialization. Signup and view all the answers

What is the first index of an array in C?

0 Signup and view all the answers

To access the last element of an array with size N, which index should be used?

N-1 Signup and view all the answers

In the provided example, how are elements accessed in the array 'myfirstarray'?

By placing the index in square brackets after the name. Signup and view all the answers

Which of the following is NOT correct regarding array initialization in C?

You must specify the size during initialization. Signup and view all the answers

What error will occur if you try to access an index equal to the array size?

You will receive a segmentation fault or out-of-bounds error. Signup and view all the answers

What is the purpose of the variable 'S' in the algorithm 'SumArray'?

To hold the total sum of the array elements. Signup and view all the answers

Study Notes

Chapter 5: Arrays

Arrays are linear data structures storing elements of the same type.
Array size is constant.
One-dimensional arrays: have a single index.
Two-dimensional arrays (matrices or 2D arrays): require two indices (row and column).
Arrays use contiguous memory locations.
Arrays size is known at compile time.

Outcomes

Students will be able to define, declare, and fill one-dimensional arrays.
Students will be able to define, declare, and fill two-dimensional arrays.
Students will know how to read array and matrix elements using algorithms and C programs.

Why Use Arrays?

Storing multiple data items efficiently is more effective than using individual variables (for example, storing 100 student marks).
Arrays avoid declaring 100 variables.

Arrays Definition

Arrays are linear data structures holding elements of the same type (homogeneous).
Array size must be fixed.
One-dimensional arrays are used in this course, in addition to two-dimensional arrays.

1D Arrays Declaration

A one-dimensional array has a single column, each element can be accessed by a single index.
The compiler needs the number of elements to reserve memory.
Algorithm Example: <ArrayName>: Array [1..<Size>] of <DataType>
C Program Example: <DataType> <ArrayName> [ <Size>];
int A1 [100];
Index values start at 0 in C.

1D Arrays Representation

Algorithm representation: Abc[1], Abc[2], ..., Abc[10].
C language representation: Abc[0], Abc[1], ..., Abc[9].
Element access: Abc[i], where i is the index/position.
Index can be an arithmetic expression (e.g. Abc[i+2], Abc[i*2+j]).

Arrays Representation (Usage)

Array elements can be used in expressions, assignment statements, output operations, and input operations.

Arrays Physical and Logical Sizes

Physical size: The total number of slots reserved in memory.
Logical size: The number of slots actually occupied in the array.
Logical size must be less than or equal to physical size.

1D Arrays Declaration - Example 1

Declare an array of 4 floats: float Mark[4];
First index is 0, Last index is length-1

1D Arrays Initialization- Remarks

Arrays can be initialized during declaration: float Mark[4] = {88.5, 64, 90.25, 100};
In initialization, the array size can often be omitted. The compiler determines the size based on the number of initial values.

1D Arrays Data Access

Accessing elements using index: Mark[1], where 1 is the index.
First index starts from 0, last element has index (n-1). (n = size of array)

1D Arrays Data Access – Example 2

C Code example for accessing and filling elements.

1D Arrays - Example 3

Algorithm and C program to read, compute the sum, and display N elements of an array.

1D Arrays - Example 4

Algorithm and C program to read elements, count null/zero elements, and display the count

Exercise 1

Given two arrays, calculate their schtroumpf (multiply elements and sum).

Exercise 2 (To Do)

Algorithm to fill an array, find the greatest value and its position.

Two-Dimensional Arrays (2D)

Simplest form of multi-dimensional arrays, often called matrices.
Two indices required to access an element; row index and column index.

2D Arrays in Algorithms

Visual representation of 2D array structure using rows and columns.

2D Arrays in C Programming

C representation of 2D arrays in memory. Explanation of indices starting at 0.

2D Arrays Declaration

Algorithm and C syntax for declaring two-dimensional arrays.
Specifying row and column sizes.

2D Arrays Initialization

How to initialize 2D arrays in algorithms and C.
Ways to specify values during declaration.

2D Arrays Data Access

Explain how to access elements using row and column indices.
Example C program for populating and displaying the values in a 2D array.
Loops to process rows and columns for accessing data.

Exercise 3

Algorithm to read elements, and find sum of main diagonal elements of a matrix.

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Description

Explore the fundamentals of arrays in programming through this quiz. Learn about one-dimensional and two-dimensional arrays, their structure, and how to manipulate them using algorithms and C programs. Test your understanding of these linear data structures and their applications.