Any sorting algorithm that uses the main memory exclusively during the sort is known as an internal sorting algorithm. In Internal sorting, the data can be accessed extremely fast and randomly. The internal sorting technique is used when data items are less than enough to be held in the main memory (RAM).

## Algorithms Used for Internal Sort

### Bubble Sort

In bubble sort, If the adjacent elements are in the wrong order, this technique works by comparing adjacent elements and repeatedly swapping them until all elements are in the correct order. The Bubble sort algorithm is not suitable for large data sets as its average and worst-case time complexity is quite high it’s O(n^{2}) and used the main memory in each swap.

The whole list is traversed by the algorithm until the list is completely sorted:

### Insertion Sort

Insertion sort is a sorting method in which each element is moved one at a time to the correct position. It is an algorithm that, after each iteration, puts an unsorted element in the right position. The Insertion sorting algorithm works similarly to the way we sort playing cards in our hands.

Virtually, the dataset is divided into a sorted part and an unsorted part.

what is an internal sorting algorithm (Insertion sort):

### Quick Sort

Quick sort is one of the most efficient sorting algorithms and is based on the **divide and conquer algorithm**. An element is picked by this sorting algorithm, generally known as **pivot**, and an array is partitioned into two sub-arrays one sub-array is less than the pivot element and the other sub-array is greater than the pivot element.

In order to sort the dataset as indicated below, the same procedure is repeated for sub-arrays:

what is an internal sorting algorithm (Quick Sort):

## Difference Between Internal and External Sort

Internal Sort | External Sort |
---|---|

Internal sorting is used when the input data can be adjusted in the main memory all at once. | External sorting is used when the input data cannot be adjusted in the main memory all at once. |

The data to be sorted should be small enough to fit in the main memory. | It is used when data to be sorted cannot fit into the main memory all at once. |

The storage device used in this method is only main memory (RAM) | Both Secondary memory (Hard Disk) and Main memory are used in this method. |

While sorting is in progress, all the data to be sorted is stored in the main memory at all times. | While sorting, data is loaded into the Main memory in small chunks, all data is stored outside the memory like on Hard Disk. |

Algorithms Used for Internal Sort are Bubble sort, Insertion Sort, Quick sort, Heap sort, etc. | Algorithms Used for External Sort are Merge sort, Tape Sort, External radix sort, etc. |

## Conclusion

- what is an internal sorting algorithm: Any sorting algorithm that uses the main memory exclusively during the sort is known as an internal sorting algorithm.
- The internal sorting technique is used when data items are less than enough to be held in the main memory (RAM) and the data can be accessed randomly.
- Bubble sort works by comparing adjacent elements, and repeatedly swapping them until all elements are in the correct order.
- Quick sort is one of the most efficient sorting algorithms and is based on the divide and conquer approach.
- While sorting is in progress, all the data to be sorted is stored in the main memory at all times in the internal sort whereas data is loaded in small chunks in the main memory in the external sort.