GATE CS 2002 Q2.22 — File Systems

In an indexed allocation scheme, a file's directory entry points to an index block (or a set of index blocks) containing pointers to the actual data blocks of the file.

To determine the maximum possible size of a file, we need to calculate the maximum number of data blocks that can be addressed. Let us define the key parameters:

• Block Size ($B$): The size of each disk block (in bytes).
• Block Address Size ($A$): The number of bytes required to store a single disk block address.
• Number of Index Blocks ($N$): The total number of blocks allocated to hold the index pointers (which can be organized as a single block, linked index blocks, or multi-level index blocks).

Using these parameters:

1. The number of pointers that can fit into a single index block is given by $\lfloor B / A \rfloor$. This directly depends on the size of the blocks ($B$) and the size of the address of the blocks ($A$).
2. The total number of data blocks that can be indexed is determined by the number of blocks used for the index ($N$) multiplied by the capacity of each index block.
3. Finally, the maximum file size is calculated as: $$\text{Maximum File Size} = (\text{Total addressable data blocks}) \times B$$

Thus, the maximum possible file size depends on all three factors: the size of the blocks, the number of blocks used for the index, and the size of the address of the blocks.

Therefore, the correct option is C.