COP4600 Computer Science Module 7 Lecture 3 Flashcards on Memory Allocation

Contiguous Allocation Acronym

All-in-a-Row

Linked List Allocation Acronym

Block

Chained Table Allocation Acronym

FAT

Indexed Allocation Acronym

Index Nodes

Chained Index Allocation Acronym

Index and Linked List

Multi-Level Indexed Allocation Acronym

Tree Structure

Contiguous Allocation

A file's contents are stored in order on the drive; all blocks of a file are kept together contiguously.

What may contiguous allocation suffer from?

External fragmentation.

Why may problems arise in contiguous allocation?

If files grow or if the exact size of a file is unknown at creation time.

Linked List Allocation

Each block holds a pointer to the next.

Why is there no external fragmentation in linked list allocation?

Because blocks of a file do not have to be contiguous, and block sizes are fixed.

What is linked list allocation efficient and inefficient for?

Efficient for sequential access files, but not for random access (must traverse all links).

What is a big problem with linked allocation?

A pointer can be lost or damaged. Doubly linked lists provide some protection, at the cost of additional overhead and wasted space.

Chained Table Allocation

The linked list is chain stored in a table to minimize disk accesses.

Indexed Allocation

Stores locations of each block in an index block referenced by the file control block.

What is limited in a pure index system?

The file size.

Multi-Level Indexed Allocation

We can use direct and indirect blocks to increase maximum file size.

Chained Indexed Allocation

Direct blocks can be used with an additional indirect pointer.

In contiguous file allocation schemes, the content of files are stored...

...purely in order on the drive.

(T/F) Performance of contiguous file allocation schemes are good.

TRUE

Contiguous file allocation may suffer from...

...fragmentation.

In the linked list allocation scheme, reliability partially depends on the pointers...

...not getting lost.

What is an improvement made in chained table allocation (FAT)?

The FAT table can be cached in memory, greatly improving random access speeds.

Indexed allocation stores locations of each block...

...in an index block referenced by the FCB.

Fill in the Blank:

We can use ______ and ________ blocks to increase maximum file size.

1. direct

2. indirect

Fill in the Blank:

Some systems use contiguous access for _____ _____ and an indexed scheme when ____ _____ surpass a certain _________.

1. small

2. files

3. file

4. sizes

5. threshold