Working with Shared Libraries | Set 1 Last Updated : 23 Jul, 2025 Comments Improve Suggest changes Like Article Like Report This article is not for those algo geeks. If you are interested in systems related stuff, just read on... Shared libraries are useful in sharing code which is common across many applications. For example, it is more economic to pack all the code related to TCP/IP implementation in a shared library. However, data can't be shared as every application needs its own set of data. Applications like, browser, ftp, telnet, etc... make use of the shared 'network' library to elevate specific functionality. Every operating system has its own representation and tool-set to create shared libraries. More or less the concepts are same. On Windows every object file (*.obj, *.dll, *.ocx, *.sys, *.exe etc...) follow a format called Portable Executable. Even shared libraries (called as Dynamic Linked Libraries or DLL in short) are also represented in PE format. The tool-set that is used to create these libraries need to understand the binary format. Linux variants follow a format called Executable and Linkable Format (ELF). The ELF files are position independent (PIC) format. Shared libraries in Linux are referred as shared objects (generally with extension *.so). These are similar to DLLs in Windows platform. Even shared object files follow the ELF binary format. Remember, the file extensions (*.dll, *.so, *.a, *.lib, etc...) are just for programmer convenience. They don't have any significance. All these are binary files. You can name them as you wish. Yet ensure you provide absolute paths in building applications. In general, when we compile an application the steps are simple. Compile, Link and Load. However, it is not simple. These steps are more versatile on modern operating systems. When you link your application against static library, the code is part of your application. There is no dependency. Even though it causes the application size to increase, it has its own advantages. The primary one is speed as there will be no symbol (a program entity) resolution at runtime. Since every piece of code part of the binary image, such applications are independent of version mismatch issues. However, the cost is on fixing an issue in library code. If there is any bug in library code, entire application need to be recompiled and shipped to the client. In case of dynamic libraries, fixing or upgrading the libraries is easy. You just need to ship the updated shared libraries. The application need not to recompile, it only need to re-run. You can design a mechanism where we don't need to restart the application. When we link an application against a shared library, the linker leaves some stubs (unresolved symbols) to be filled at application loading time. These stubs need to be filled by a tool called, dynamic linker at run time or at application loading time. Again loading of a library is of two types, static loading and dynamic loading. Don't confuse between static loading vs static linking and dynamic loading vs dynamic linking. For example, you have built an application that depends on libstdc++.so which is a shared object (dynamic library). How does the application become aware of required shared libraries? (If you are interested, explore the tools tdump from Borland tool set, objdump or nm or readelf tools on Linux). Static loading: In static loading, all of those dependent shared libraries are loaded into memory even before the application starts execution. If loading of any shared library fails, the application won't run.A dynamic loader examines application's dependency on shared libraries. If these libraries are already loaded into the memory, the library address space is mapped to application virtual address space (VAS) and the dynamic linker does relocation of unresolved symbols.If these libraries are not loaded into memory (perhaps your application might be first to invoke the shared library), the loader searches in standard library paths and loads them into memory, then maps and resolves symbols. Again loading is big process, if you are interested write your own loader :). While resolving the symbols, if the dynamic linker not able to find any symbol (maybe due to older version of shared library), the application can't be started. Dynamic Loading: As the name indicates, dynamic loading is about loading of library on demand.For example, if you want a small functionality from a shared library. Why should it be loaded at the application load time and sit in the memory? You can invoke loading of these shared libraries dynamically when you need their functionality. This is called dynamic loading. In this case, the programmer aware of situation 'when should the library be loaded'. The tool-set and relevant kernel provides API to support dynamic loading, and querying of symbols in the shared library. More details in later articles. Note: If you come across terms like loadable modules or equivalent terms, don't mix them with shared libraries. They are different from shared libraries The kernels provide framework to support loadable modules. Working with Shared Libraries | Set 2 Exercise: 1. Assuming you have understood the concepts, How do you design an application (e.g. Banking) which can upgrade to new shared libraries without re-running the application. — Venki. Comment More infoAdvertise with us Next Article What is an Operating System? K kartik Follow Improve Article Tags : Operating Systems system-programming memory-management Similar Reads Operating System Tutorial An Operating System(OS) is a software that manages and handles hardware and software resources of a computing device. Responsible for managing and controlling all the activities and sharing of computer resources among different running applications.A low-level Software that includes all the basic fu 4 min read OS BasicsWhat is an Operating System?An Operating System is a System software that manages all the resources of the computing device. Acts as an interface between the software and different parts of the computer or the computer hardware. Manages the overall resources and operations of the computer. Controls and monitors the execution o 5 min read Types of Operating SystemsAn operating system (OS) is software that manages computer hardware and software resources. It acts as a bridge between users and the computer, ensuring smooth operation. 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The structure of the OS depends mainly on how the various standard components of the operating system are interconnected and merge into the kernel. This article discusses a variety of operating system implementation structu 9 min read Booting and Dual Booting of Operating SystemWhen a computer or any other computing device is in a powerless state, its operating system remains stored in secondary storage like a hard disk or SSD. But, when the computer is started, the operating system must be present in the main memory or RAM of the system in order to perform all the functio 6 min read System CallA system call is a programmatic way in which a computer program requests a service from the kernel of the operating system on which it is executed. System Calls are,A way for programs to interact with the operating system. Provide the services of the operating system to the user programs.Only entry 9 min read Process & ThreadsIntroduction of Process ManagementProcess Management for a single tasking or batch processing system is easy as only one process is active at a time. With multiple processes (multiprogramming or multitasking) being active, the process management becomes complex as a CPU needs to be efficiently utilized by multiple processes. Multipl 8 min read Process Table and Process Control Block (PCB)While creating a process, the operating system performs several operations. To identify the processes, it assigns a process identification number (PID) to each process. As the operating system supports multi-programming, it needs to keep track of all the processes. For this task, the process control 6 min read Process Schedulers in Operating SystemA process is the instance of a computer program in execution. Scheduling is important in operating systems with multiprogramming as multiple processes might be eligible for running at a time. One of the key responsibilities of an Operating System (OS) is to decide which programs will execute on the 6 min read Context Switching in Operating SystemContext Switching in an operating system is a critical function that allows the CPU to efficiently manage multiple processes. By saving the state of a currently active process and loading the state of another, the system can handle various tasks simultaneously without losing progress. This switching 4 min read Thread in Operating SystemA thread is a single sequence stream within a process. Threads are also called lightweight processes as they possess some of the properties of processes. Each thread belongs to exactly one process.In an operating system that supports multithreading, the process can consist of many threads. But threa 7 min read CPU SchedulingCPU Scheduling in Operating SystemsCPU scheduling is a process used by the operating system to decide which task or process gets to use the CPU at a particular time. This is important because a CPU can only handle one task at a time, but there are usually many tasks that need to be processed. The following are different purposes of a 8 min read Preemptive and Non-Preemptive SchedulingIn operating systems, scheduling is the method by which processes are given access the CPU. Efficient scheduling is essential for optimal system performance and user experience. There are two primary types of CPU scheduling: preemptive and non-preemptive. Understanding the differences between preemp 4 min read Multiple-Processor Scheduling in Operating SystemIn multiple-processor scheduling multiple CPUs are available and hence Load Sharing becomes possible. However multiple processor scheduling is more complex as compared to single processor scheduling. 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It ensures that a system remains in a safe state by carefully allocating resources to processes while avoiding unsafe states that could lead to deadlocks.The Banker's Algorithm is a smart way for 8 min read Wait For Graph Deadlock Detection in Distributed SystemDeadlocks are a fundamental problem in distributed systems. A process may request resources in any order and a process can request resources while holding others. A Deadlock is a situation where a set of processes are blocked as each process in a Distributed system is holding some resources and that 5 min read Deadlock Prevention And AvoidanceDeadlock prevention and avoidance are strategies used in computer systems to ensure that different processes can run smoothly without getting stuck waiting for each other forever. Think of it like a traffic system where cars (processes) must move through intersections (resources) without getting int 5 min read Deadlock Detection And RecoveryDeadlock Detection and Recovery is the mechanism of detecting and resolving deadlocks in an operating system. In operating systems, deadlock recovery is important to keep everything running smoothly. A deadlock occurs when two or more processes are blocked, waiting for each other to release the reso 6 min read Deadlock Ignorance in Operating SystemIn this article we will study in brief about what is Deadlock followed by Deadlock Ignorance in Operating System. What is Deadlock? If each process in the set of processes is waiting for an event that only another process in the set can cause it is actually referred as called Deadlock. In other word 5 min read Memory & Disk ManagementMemory Management in Operating SystemMemory is a hardware component that stores data, instructions and information temporarily or permanently for processing. It consists of an array of bytes or words, each with a unique address. Memory holds both input data and program instructions needed for the CPU to execute tasks.Memory works close 7 min read Fixed (or static) Partitioning in Operating SystemFixed partitioning, also known as static partitioning, is one of the earliest memory management techniques used in operating systems. In this method, the main memory is divided into a fixed number of partitions at system startup, and each partition is allocated to a process. These partitions remain 8 min read Variable (or Dynamic) Partitioning in Operating SystemIn operating systems, Memory Management is the function responsible for allocating and managing a computer’s main memory. The memory Management function keeps track of the status of each memory location, either allocated or free to ensure effective and efficient use of Primary Memory. Below are Memo 4 min read Paging in Operating SystemPaging is the process of moving parts of a program, called pages, from secondary storage (like a hard drive) into the main memory (RAM). The main idea behind paging is to break a program into smaller fixed-size blocks called pages.To keep track of where each page is stored in memory, the operating s 8 min read Segmentation in Operating SystemA process is divided into Segments. The chunks that a program is divided into which are not necessarily all of the exact sizes are called segments. Segmentation gives the user's view of the process which paging does not provide. Here the user's view is mapped to physical memory. Types of Segmentatio 4 min read Segmentation in Operating SystemA process is divided into Segments. The chunks that a program is divided into which are not necessarily all of the exact sizes are called segments. Segmentation gives the user's view of the process which paging does not provide. Here the user's view is mapped to physical memory. Types of Segmentatio 4 min read Page Replacement Algorithms in Operating SystemsIn an operating system that uses paging for memory management, a page replacement algorithm is needed to decide which page needs to be replaced when a new page comes in. Page replacement becomes necessary when a page fault occurs and no free page frames are in memory. in this article, we will discus 7 min read File Systems in Operating SystemA computer file is defined as a medium used for saving and managing data in the computer system. The data stored in the computer system is completely in digital format, although there can be various types of files that help us to store the data.File systems are a crucial part of any operating system 8 min read File Systems in Operating SystemA computer file is defined as a medium used for saving and managing data in the computer system. The data stored in the computer system is completely in digital format, although there can be various types of files that help us to store the data.File systems are a crucial part of any operating system 8 min read Advanced OSMultithreading in Operating SystemA thread is a path that is followed during a program’s execution. The majority of programs written nowadays run as a single thread. For example, a program is not capable of reading keystrokes while making drawings. These tasks cannot be executed by the program at the same time. This problem can be s 7 min read Compaction in Operating SystemCompaction is a technique to collect all the free memory present in the form of fragments into one large chunk of free memory, which can be used to run other processes. It does that by moving all the processes towards one end of the memory and all the available free space towards the other end of th 3 min read Belady's Anomaly in Page Replacement AlgorithmsBelady's Anomaly is a phenomenon in operating systems where increasing the number of page frames in memory leads to an increase in the number of page faults for certain page replacement algorithms. Normally, as more page frames are available, the operating system has more flexibility to keep the nec 11 min read Techniques to handle ThrashingPrerequisite - Virtual Memory Thrashing is a condition or a situation when the system is spending a major portion of its time servicing the page faults, but the actual processing done is very negligible. Causes of thrashing:High degree of multiprogramming.Lack of frames.Page replacement policy.Thras 6 min read Free Space Management in Operating SystemFree space management is a critical aspect of operating systems as it involves managing the available storage space on the hard disk or other secondary storage devices. The operating system uses various techniques to manage free space and optimize the use of storage devices. Here are some of the com 7 min read RAID (Redundant Arrays of Independent Disks)RAID is a technique that combines multiple hard drives or SSDs into a single system to improve performance, data safety, or both. If one drive fails, data can still be recovered from the others.RAID helps store data more reliably and efficiently by spreading or copying data across drives. Different 13 min read PracticeLast Minute Notes – Operating SystemsAn Operating System (OS) is a system software that manages computer hardware, software resources, and provides common services for computer programs. It acts as an interface between the user and the computer hardware.Table of Content Types of Operating System (OS): ThreadsProcessCPU Scheduling Algor 15+ min read Operating System Interview QuestionsAn operating system acts as a GUI between the user and the computer system. In other words, an OS acts as an intermediary between the user and the computer hardware, managing resources such as memory, processing power, and input/output operations. Here some examples of popular operating systems incl 15+ min read Operating Systems - GATE CSE Previous Year QuestionsThe Operating System(OS) subject has high importance in GATE CSE exam because:large number of questions nearly 10-12% of the total asked significant weightage (9-11 marks) across multiple years which can also be seen in the below given table:YearApprox. Marks from OSNumber of QuestionsDifficulty Lev 2 min read Like