L-5.3: Internal Fragmentation | Fixed size Partitioning | Memory management | Operating System

Summary

The video script discusses Fixed Partitioning, an early memory allocation method where RAM is divided into a fixed number of partitions. It explains the concept with diagrams, illustrating how processes are allocated to these fixed-size slots, leading to internal fragmentation when processes don't fully utilize a partition. The script also covers external fragmentation, which occurs when a process can't be accommodated despite available memory due to the contiguous allocation constraint. The method's simplicity is highlighted, but its limitations, including a fixed degree of multiprogramming and process size restrictions, are critiqued. The script concludes by noting the method's historical use in mainframes and its simplicity, despite its drawbacks.

Takeaways

• 📚 Fixed Partitioning, also known as Static Partitioning, is a method of contiguous memory allocation where the RAM is divided into a fixed number of partitions.
• 🖥️ The Operating System occupies a portion of the RAM, and the remaining space is divided into fixed partitions for process allocation.
• 🔢 The number of partitions is fixed during system configuration, but the size of each partition can be the same or different.
• 🚫 Contiguous allocation does not allow for spanning, meaning a process must fit entirely within one partition or not at all.
• 💾 Internal Fragmentation occurs when a process occupies a partition but does not use all of its space, leading to wasted memory.
• 🚫 There is a limit on the size of processes that can be accommodated, as it cannot exceed the size of the largest partition.
• 🔑 The Degree of Multiprogramming is limited by the number of fixed partitions, restricting the number of processes that can be in RAM at one time.
• 🔄 External Fragmentation happens when there is enough total free memory across partitions to accommodate a new process, but no single partition is large enough to hold it.
• 🛠️ Fixed Partitioning was easier to implement in the past, especially in mainframes, but it has several limitations leading to its reduced use in modern systems.
• 📈 The script suggests that while Fixed Partitioning has its advantages, such as simplicity, it also presents significant challenges like Internal and External Fragmentation, and limitations on process size and multiprogramming degree.

Q & A

What is Fixed Partitioning in memory allocation?

Fixed Partitioning, also known as Static Partitioning, is a method in contiguous memory allocation where the RAM is divided into a fixed number of partitions of either the same or different sizes before the system starts. Processes are then allocated to these partitions.

Why is the number of partitions in Fixed Partitioning considered important?

The number of partitions is important because it determines how the RAM is divided and how many processes can be accommodated. Each partition can only hold one process at a time, and the size of the partitions dictates the size of the processes that can be accommodated.

What is the concept of Internal Fragmentation in Fixed Partitioning?

Internal Fragmentation occurs when a process occupies an entire partition but does not fully utilize its memory, leaving some memory space unused. This happens because processes must fit entirely within a partition and cannot span across multiple partitions.

Can you explain the External Fragmentation issue mentioned in the script?

External Fragmentation happens when there is a sum of free memory in different partitions that is sufficient to accommodate a new process, but the process cannot be allocated because the free memory is not contiguous. This is due to the constraint of contiguous allocation in Fixed Partitioning.

What is the limitation on process size in Fixed Partitioning?

The limitation on process size in Fixed Partitioning is determined by the maximum size of the partitions. If a process requires more memory than the largest partition, it cannot be accommodated, regardless of the total available memory.

How does Fixed Partitioning affect the Degree of Multiprogramming?

Fixed Partitioning limits the Degree of Multiprogramming because the number of partitions dictates the maximum number of processes that can be simultaneously loaded into the RAM. If the number of partitions is fixed, it restricts the number of processes that can be run concurrently.

What are the advantages of using Fixed Partitioning?

Fixed Partitioning is easy to implement because the number and size of partitions are predetermined, making the allocation and deallocation of memory straightforward. It was commonly used in the 1960s with mainframes where system configuration was done beforehand.

Why is Fixed Partitioning not used today?

Fixed Partitioning is not used today due to its inefficiencies, such as Internal and External Fragmentation, and the limitations it imposes on process size and Degree of Multiprogramming. Modern systems use more flexible memory management techniques like Dynamic Partitioning and Paging.

How does the size of partitions in Fixed Partitioning affect memory utilization?

If partitions are of fixed sizes, it can lead to underutilization of memory if processes are smaller than the partition size, causing Internal Fragmentation. Conversely, if partitions are too small, they might not accommodate larger processes, leading to External Fragmentation.

What are the disadvantages of Fixed Partitioning as discussed in the script?

The disadvantages of Fixed Partitioning include Internal Fragmentation, External Fragmentation, a limitation on process size, and a limitation on the Degree of Multiprogramming. These issues reduce the efficiency of memory utilization and the flexibility of the system.