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Arrays : Definition and Classification of Arrays

✅ Arrays: Definition and Classification

✅ 1. Definition of Array

An Array is a linear data structure used to store multiple values of the same data type in continuous (contiguous) memory locations.

✅ Each element in an array is accessed using an index (subscript).

📌 Example:

int a[5] = {10, 20, 30, 40, 50};

✅ Here:

  • a is the array name
  • 5 is the size
  • 10, 20, 30, 40, 50 are elements
  • Index starts from 0

📌 Indexing:

  • a[0] = 10
  • a[1] = 20
  • a[2] = 30
  • a[3] = 40
  • a[4] = 50

✅ 2. Characteristics / Features of Array

✅ Important points:

  1. Stores similar type elements (same data type)
  2. Stored in contiguous memory
  3. Elements are accessed using index
  4. Allows random access (direct access)
  5. Size is usually fixed (static)

✅ 3. Classification of Arrays

Arrays are classified mainly into the following types:

✅ (A) One-Dimensional Array (1D Array)

A 1D array stores elements in a single row (linear form).

✅ Syntax:

datatype array_name[size];

✅ Example:

int marks[5];

📌 Representation:

marks[0]  marks[1]  marks[2]  marks[3]  marks[4]

✅ Uses:

  • Storing list of marks
  • Roll numbers
  • Temperatures of a week, etc.

✅ (B) Two-Dimensional Array (2D Array)

A 2D array stores elements in rows and columns (matrix form).

✅ Syntax:

datatype array_name[rows][cols];

✅ Example:

int matrix[2][3];

📌 Representation:

Row 0 →  a[0][0]  a[0][1]  a[0][2]
Row 1 →  a[1][0]  a[1][1]  a[1][2]

✅ Uses:

  • Matrix calculations
  • Tables
  • Storing marks of multiple students in subjects

✅ (C) Three-Dimensional Array (3D Array)

A 3D array stores elements in multiple layers (3 dimensions).

✅ Syntax:

datatype array_name[x][y][z];

✅ Example:

int arr[2][3][4];

📌 Uses:

  • Advanced matrix operations
  • 3D graphics
  • Scientific calculations

✅ (D) Multi-Dimensional Array

Arrays with more than 2 dimensions are called multi-dimensional arrays.

✅ Example:

  • 4D array, 5D array etc. (rare in basic programs)

✅ 4. Other Classification (Very Useful for Exams)

✅ 1. Static Array

A Static Array has a fixed size, decided at compile time.

✅ Example:

int a[10];

📌 Advantage:

  • Easy access and fast indexing

📌 Disadvantage:

  • Size cannot be changed

✅ 2. Dynamic Array

A Dynamic Array can grow or shrink during runtime using dynamic memory allocation.

✅ Example in C using malloc:

int *a = (int*)malloc(n * sizeof(int));

📌 Advantage:

  • Memory is used efficiently

📌 Disadvantage:

  • Complex handling

✅ 5. Advantages of Arrays

✅ Benefits:

  • Easy to store and access data
  • Fast access using index (random access)
  • Simple to use in loops
  • Useful for implementing stacks, queues, matrices

✅ 6. Disadvantages of Arrays

❌ Limitations:

  • Fixed size (in static arrays)
  • Insertion and deletion are difficult (need shifting)
  • Wastage of memory if size is larger
  • Stores only same data type elements

✅ Conclusion

An array is a linear data structure that stores similar type elements in continuous memory locations. Arrays are mainly classified as 1D, 2D, 3D and multi-dimensional arrays, and also as static and dynamic arrays, based on memory allocation.

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