Memory management pdf

This PDF will help the reader to better understand how to manage memory in the C programming language. It also helps the reader to recognize problems that may occur in this process.

C programming memory management is a set of techniques for managing memory in the C programming language. Also, the C programming language is a programming language that has been widely used since the s and is still being today.

As mentioned earlier, the C programming language emerged in This language is to be one of the most important languages because it is simple and easy to use. It has been widely used in embedded systems and operating systems. This document can be a reference for students, professionals, and even teachers who are in learning about the C programming language.

For students, this PDF will help them understand how to manage memory in C programming. For teachers, this document provides a way to teach students about memory management and memory leak problems, which are important concepts when it comes to handling memory.

As for professionals, this PDF can be a guide to help them identify the issues that may arise during the process of managing memory in the C programming language. As a result, it is an important topic to be studied. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.

Objectives The main objective of this PDF is to provide an overview of the basic functions provided by the C language for memory management. The following are some of the methods used by this PDF: provides an overview of the C programming language and how it is by a compiler. C Programming Memory Management: What is it? History As mentioned earlier, the C programming language emerged in C Programming Memory Management PDF: How to use it This document can be a reference for students, professionals, and even teachers who are in learning about the C programming language.

Click to rate this post! Next Programming For Environmental Management. Leave a Reply Cancel reply Your email address will not be published. Leave this field empty. A stub is a small piece of code. When the stub is executed, it checks whether the needed routine is already in memory or not. If not available then the program loads the routine into memory.

Swapping : When a process is executed it must have resided in memory. Swapping is a process of swap a process temporarily into a secondary memory from the main memory, which is fast as compared to secondary memory. A swapping allows more processes to be run and can be fit into memory at one time. The main part of swapping is transferred time and the total time directly proportional to the amount of memory swapped. Swapping is also known as roll-out , roll in, because if a higher priority process arrives and wants service, the memory manager can swap out the lower priority process and then load and execute the higher priority process.

After finishing higher priority work, the lower priority process swapped back in memory and continued to the execution process. Contiguous Memory Allocation : The main memory should oblige both the operating system and the different client processes.

Therefore, the allocation of memory becomes an important task in the operating system. The memory is usually divided into two partitions: one for the resident operating system and one for the user processes.

We normally need several user processes to reside in memory simultaneously. Therefore, we need to consider how to allocate available memory to the processes that are in the input queue waiting to be brought into memory.

In adjacent memory allotment, each process is contained in a single contiguous segment of memory. Memory allocation: To gain proper memory utilization, memory allocation must be allocated efficient manner. One of the simplest methods for allocating memory is to divide memory into several fixed-sized partitions and each partition contains exactly one process. Thus, the degree of multiprogramming is obtained by the number of partitions.

Multiple partition allocation : In this method, a process is selected from the input queue and loaded into the free partition. When the process terminates, the partition becomes available for other processes. Fixed partition allocation: In this method, the operating system maintains a table that indicates which parts of memory are available and which are occupied by processes.

Initially, all memory is available for user processes and is considered one large block of available memory. When the process arrives and needs memory, we search for a hole that is large enough to store this process. If the requirement fulfills then we allocate memory to process, otherwise keeping the rest available to satisfy future requests. While allocating a memory sometimes dynamic storage allocation problems occur, which concerns how to satisfy a request of size n from a list of free holes.

There are some solutions to this problem: First fit:- In the first fit, the first available free hole fulfills the requirement of the process allocated. Here, in this diagram 40 KB memory block is the first available free hole that can store process A size of 25 KB , because the first two blocks did not have sufficient memory space. Best fit:- In the best fit, allocate the smallest hole that is big enough to process requirements. For this, we search the entire list, unless the list is ordered by size.

Here in this example, first, we traverse the complete list and find the last hole 25KB is the best suitable hole for Process A size 25KB. In this method memory utilization is maximum as compared to other memory allocation techniques. Worst fit:- In the worst fit, allocate the largest available hole to process. This method produces the largest leftover hole. Inefficient memory utilization is a major issue in the worst fit.

Fragmentation: A Fragmentation is defined as when the process is loaded and removed after execution from memory, it creates a small free hole. These holes can not be assigned to new processes because holes are not combined or do not fulfill the memory requirement of the process. To achieve a degree of multiprogramming, we must reduce the waste of memory or fragmentation problem.

In operating system two types of fragmentation: Internal fragmentation:. Internal fragmentation occurs when memory blocks are allocated to the process more than their requested size. Due to this some unused space is leftover and creates an internal fragmentation problem. Example: Suppose there is a fixed partitioning is used for memory allocation and the different size of block 3MB, 6MB, and 7MB space in memory. Now a new process p4 of size 2MB comes and demand for the block of memory.

It gets a memory block of 3MB but 1MB block memory is a waste, and it can not be allocated to other processes too. This is called internal fragmentation. External fragmentation: In external fragmentation, we have a free memory block, but we can not assign it to process because blocks are not contiguous. After allocating process p1 process and p2 process left 1MB and 2MB. Suppose a new process p4 comes and demands a 3MB block of memory, which is available, but we can not assign it because free memory space is not contiguous.

This is called external fragmentation. Both the first fit and best-fit systems for memory allocation affected by external fragmentation. To overcome the external fragmentation problem Compaction is used. In the compaction technique, all free memory space combines and makes one large block.

So, this space can be used by other processes effectively. Another possible solution to the external fragmentation is to allow the logical address space of the processes to be noncontiguous, thus permit a process to be allocated physical memory where ever the latter is available.

Paging: Paging is a memory management scheme that eliminates the need for contiguous allocation of physical memory. This scheme permits the physical address space of a process to be non-contiguous.

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