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Operating System Unit 1

The document provides an overview of operating systems (OS), detailing their roles and components such as memory management, processor management, device management, and file management. It categorizes OS into types, including batch, interactive, real-time, hybrid, and embedded systems, while also discussing the historical development and advancements from mainframes to modern microcomputers and virtualization technologies. Key concepts such as multiprogramming, threading, and the kernel are explained, highlighting the evolution of OS functionality and architecture.

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Overview of Operating Systems• User Interface•Memory Management•
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OPERATING SYSTEMS- 16SCCCA6 UNIT I PREPARED BY, V.SANTHI ASSISTANT PROFESSOR DEPT.OF COMPUTER APPLICATIONS, BON SECOURS COLLEGE FOR WOMEN, THANJAVUR.
WHAT IS OS? • An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
EXAMPLE OS: • Windows 7 • Windows 10 • Windows XP • Apple's macOS • Linux
OS SOFTWARE: • User Interface • Memory manager • File manager • Processor manager • Device Manager User Interface Device Manager Processor manager Memory manager File manager
BASE OF A PYRAMID FOR A NETWORKED OS: • It’s the additional part of the OS Manager. • When n/w needed we can connect . • N/W not always an Integral part of Operating system. • Most of the Operating System Routinely supports N/w Manager Process manager Device manager File manager Network manager memory manager Keyboar d, printer CPU Network communica tions, Protocols Main memor y Program files, data files, compiler
COOPERATION: • Device manager processor(R/W) • Memory manager File manager •
MAIN MEMORY MANAGEMENT  The Memory Manager is in charge of main memory, also known as RAM, short for Random Access Memory. The Memory Manager checks the validity of each request for memory space and, if it is a legal request.  It allocates a portion of memory that isn’t already in use.  The Memory Manager deallocates memory.  A primary responsibility of the Memory Manager is to protect the space in main memory occupied bythe operating system itself.
PROCESSOR MANAGEMENT • The Processor Manager decides how to allocate the central processing unit (CPU). • The Processor Manager is to keep track of the status of each process. A process is defined here as an instanceof execution of a program. • The Processor Manager monitors whether the CPU is executing a process or waiting for a READ or WRITEcommand to finish execution
DEVICE MANAGEMENT  The Device Manager monitors every device, channel, and control unit. Its job is to choose the most efficient way to allocate all of the system’s devices, printers, ports, disk drives, and so forth, based on a scheduling policy chosen by the system’s designers.  The Device Manager does this by allocating each resource, starting its operation, and, finally, deallocating the device, making it available to the next process or job. •
FILE MANAGEMENT  The File Manager keeps track of every file in the system, including data files, program files, compilers, and applications.  The File Manager also controls what users are allowed to do with files once they access them.  The File Manager allocates the necessary resources and later deallocates them.
NETWORK MANAGEMENT • Operating systems with Internet or networking capability have a fifth essential manager called the Network Manager that provides a convenient way for users to share resources while controlling users’ access to them.
USER INTERFACE • Portion of the OS that users interact with directly. • Olden days, the user interface consisted of commands typed on a keyboard and displayed on a monitor.
HISTORY OF MACHINE HARDWARE • Main Memory • where the data and instructions must reside to beprocessed. • I/O Device • include everyperipheral unit in the system such as printers,disk drives, CD/DVD drives, flash memory, keyboards • CPU • brains with the circuitry (sometimes called the chip) to control the interpretation and execution of instructions.
MAIN FRAME: 1964 • Mainframe was a large machine- in size and in internal memory capacity • IBM 360 model 3 required an A.C Room and its 18 ft square to house. – its CPU 5ft high & 6 ft Wide – memory 64k • Use:bulk data processing, such as census, industry and consumer statistics,
MINI COMPUTER -1970’S • Its developed to give smaller Instructions-Size & memory capacity Smaller than main frames. • Use-Large schools & colleges, Computer centers.
SUPER COMPUTER- • Its developed for government applications-fast & massive amount of data. • Also scientific research & Oil companies.
MICRO COMPUTER- LATE 1970’S • Inexpensive –single user handling- 64k memory • Smaller than mini computer- faster & large capacity • Used for commercial-such as educational ,government & Enterprise its also called workstations. • When workstations are connected to n/w its supports engineering & technical use.ex.CAD
SERVER- (LARGE COLLECTION OF HARD DRIVES)) • Powerful computers that provide specialized services to other computers on Client /server. • E.g: print server, Internet server , e-mail server. • Manages file storage and retrieval.
• Now a days the most mainframes has multiple processor capacity Coordinated by processor manager. • Now its classified by its Processor only not by memory. • N/W is the internal part of todays modern computer, Once computer connect to the N/W ,it connect to the workstations,servers & peripheral devices.
TYPES OF OS: 5 TYPES Batch System Interactive System Real time system Hybrid System Embedded system
BATCH SYSTEM • The users of a batch operating system do not interact with the computer directly. Each user prepares his job on an off-line device like punch cards and submits it to the computer operator.
INTERACTIVE SYSTEM • An interactive operating system is one that allows the user to interact directly with the operating system while one or more programs are running. An user interface in place to allow this to happen. • Faster turnaround than batch systems but are slower than the real-time systems. They were introduced to satisfy the demands of users who needed fast turnaround when debugging their programs.
REAL TIME SYSTEM: Real time system: (tickets booking, online shopping) • A real-time operating system is an operating system intended to serve real-time applications that process data as it comes in, typically without buffer delays. Two types: • Hard real time –risk if total system failure • Soft real time -suffer performance degradation, but not total system failure, as a consequence of amissed deadline.
HYBRID SYSTEM: • Combination of batch and interactive. • User can access the system and get fast response. • Many large systems are HYBRID. • In a hybrid operating system, two operating system may execute on a single device.(Combination of batch & Interactive) The two operating systems on a computer system may include a full-fledged operating system and a lightweight operating system. Both of these operating systems would fulfill different sets of tasks depending on their capabilities
EMBEDDED SYSTEM: • An embedded operating system (OS) is a specialized operating system designed to perform a specific task for a device that is not a computer. An embedded operating system's main job is to run the code that allows the device to do its job.
HISTORY OF OS DEVELOPMENT: • 1st generation of computer- Vacuum tube technology & computers the size of classroom- each computer was unique structure & purpose. • The typical program would include every instruction needed by the computer to perform a requested task. To explicit direction • the card reader-(to begin the instruction) • The CPU-(how & were to store instructions in memory) • The Output device(how to printout the finished products) • To run a programs, programmer would have to receive the machine for the length of time. • Rudimentary OS started to take shape with creation of Macros,library programs,standered sub routines & utility programs.-Prewritten pgms, standardized I/O devices were used. • 1940’S: (1940-1955)
1950’S • 2nd generation computers(1955-1965): (Gov,business,researchers & new markets) • Computers still expensive, but for business use the usage of computer is increasing widely. • Two Improvements: • 1.computer operator hired for operate machines • 2.Job scheduling increase the productivity. • FORTRAN were run at that times. • Card reader programs & tape programs used. Tape could be mounted when card reader is busy. Factors to improve the performance of CPU: • I/O devices drum, tape drives & disks generally increased. • More available storage area occupied by group of records. • To reduce error in speed b/w I/O & CPU control unit placed b/w them to act as buffer(temporary storage). • Spooling(printing) is developed by moving offline operation printing, punching, • 2Nd generation also developed to manage prg libraries, created and maintained each data in direct access address.
1960’S: • Faster CPU but when connect to I/O devices it run slower speed. • Multiprogramming were introduced to work many programs at a time. • Multiprogramming system allowed to service one after another • But in this process end the job an execution sequence. • To over come this problem active Multiprogramming is allowed use only a CPU time. • Job/program scheduling begin with 2nd generation still continued
1970’S • 3rd generation computer had faster CPU, faster Processing speed & reduce I/O access time. • 1976 the first cray super Computer was released, it has multiprogramming schemes to increase CPU’s limited physical capacity of main memory. • The physical limitation was the development of the virtual memory-(adv) CPU process only one instruction at a time. • In this time DBMS software become popular tool-(ADV) access data In integrated manner, Minimize redundancy, simplified updating
1980’S • Increase Cost/performance of the computer . • h/w and logical functions built on easily replaceable circuit boards. • Programs are stored on ROM. • Multiprocessing & n/w Operating system(distributed system) were introduced . • N/w operating system similar single process Operating system(each program ran its local os had its own user).
1990’S • Internet usage is high, world wide wed introduced. Internet accessible by computer user. • Web accessibility and e-mail become standard features of every OS. • A house devices also perform audio, video , graphic creation and editing. • cd,dvd, projection device, color printer & high speed internet were introduced.
2000’S • computers accommodate with multiple os running in same system at same time sharing resources.(virtual machines). • Virtualization is the creation of partitions on a single server with each partition supporting a differentoperating system. • Increased processing speed the multicore(dual) processor is introduced.
THREADS • Multi-core technology helps the OS handle threads, multiactions executed at the same time. • Processor is responsible for processing each job submitted by the user. Two characteristics: • Requires main memory-access data files and I/O devices. • Passes through several states(running, waiting, ready) • Multiprogramming & virtual memory Order the processes swapped b/w main memory and secondary storage during execution.
• A thread (lightweight process) defined as a unit smaller than a process, which can be scheduled and execute. • Manipulating threads is a less time consuming than manipulating process. Some OS support Multiprocess with single thread. • Multithreading allows applications to manage separate process with several threads of control.
OBJECT ORIENTED DESIGN: • Kernel is the part of the OS the resides memory at all time. It performs most essential task of OS & kernel protect h/w from user. Early OS contained memory allocations, process scheduling , device allocation , file management all elements in single part. • Recent OS resides memory has limited to few essential functions such as process scheduling ,memory allocation, • Another part handles devices , file , n/w allocations and so on…
EARLY OS AND OBJECT ORIENTED OS
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