File allocation methods explained

 

File allocation methods

Certainly! Let's take a look at an example diagram illustrating the three file allocation methods: contiguous allocation, linked allocation, and indexed allocation.

1. Contiguous Allocation:

In contiguous allocation, each file occupies a contiguous block of storage space. Here's an example diagram showing three files (A, B, and C) allocated using contiguous allocation:

```

---------------------------

| File A |

---------------------------

| File B |

---------------------------

| File C |

---------------------------

```

2. Linked Allocation:

In linked allocation, files are divided into blocks, and each block contains a pointer to the next block in the file. Here's an example diagram showing three files (A, B, and C) allocated using linked allocation:

```

Block 1 Block 2 Block 3 Block 4

-------- -------- -------- --------

|A| --> | |B| --> | |C| --> | | NULL |

-------- -------- -------- --------

```

In this example, File A starts at Block 1 and points to Block 2, File B starts at Block 2 and points to Block 3, and File C starts at Block 3 and points to Block 4. The last block of each file contains a NULL pointer to indicate the end of the file.

3. Indexed Allocation:

In indexed allocation, each file has its own index block or table containing pointers to the actual data blocks. Here's an example diagram showing three files (A, B, and C) allocated using indexed allocation:

```

Index Block Data Blocks

------------- -------------

| File A | | Data 1 |

------------- -------------

| File B | | Data 2 |

------------- | Data 3 |

| File C | | Data 4 |

------------- -------------

```

In this example, each file (A, B, and C) has its corresponding entry in the index block, which points to the actual data blocks containing the file's contents (Data 1, Data 2, Data 3, and Data 4).

These diagrams provide a visual representation of how files are allocated using different methods. Remember that these are simplified examples, and actual file allocation may involve more complex structures and considerations.