Operating Systems and ROM

• A brand new computer is inoperable without software.
• Between application software and hardware is a software interface: an operating system.

Operating System

• An operating system is a set of programs that lies between the application software and the computer hardware.
• Operating system software is an intermediary between hardware and applications software.
• System software means all programs related to coordinating computer operations and can be used interchangeably with an operating system.
• System software includes the operating system, BIOS software, drivers, and service programs.
• Operating systems perform three functions: manage computer resources, establish a user interface, and execute and provide services for applications software.
• Users want computers and application software rather than operating systems; however, the operating system determines what software is available.
• Booting initiates most computers.

Read Only Memory (ROM)

• ROM (Read Only Memory) permanently stores data on electronic devices.
• ROM contains the programming needed to start a PC, which is essential for boot-up.
• BIOS (Basic Input/Output System) is a program stored inside the ROM that starts a computer system.
• Further, BIOS manages data flow between the computer's operating system (OS) and attached devices, such as the hard disk, video adapter, keyboard, mouse, and printer.
• The Kernel is the central module of the operating system.
• The Kernel is the first application to run in an Operating System
• Kernel is responsible for memory management, process, task, and disk management.

Batch Operating System

• This operating system does not interact with the computer directly.
• An operator sorts similar jobs into batches, considering similar needs.
• Processors of the batch systems know how long the job would be when it is in queue, and it can be difficult to guess or know the time required by any job to complete.
• Multiple users can share the batch systems.
• Idle time is minimal, and it's easier to manage large work repeatedly.
• Disadvantages include a lack of interaction between the user and the job.
• CPU is often idle because the speed of the mechanical I/O devices is slower than the CPU.
• Prioritization is difficult, batch systems are hard to debug, and other jobs wait if one fails.

Time-Sharing Operating Systems

• Tasks get a dedicated time to execute for smooth operation, known as Multitasking.
• Each user gets time from CPU, creating a single-system experience.
• Advantages are an equal opportunity for each task and reduced CPU idle time.
• Disadvantages include reliability, security/integrity of user programs/data, and data communication issues.

Distributed Operating System

• Through communication lines (high-speed buses or telephone lines), processors communicate, known as loosely coupled or distributed systems.
• Processors in the systems vary in size and function and are referred to as sites, nodes, or computers.
• The failure of one unit does not affect network communication due to the independence of systems from each other.
• Electronic mail speeds data exchange.
• Resources are shared, making computation fast and durable while reducing the load on the host computer.
• The systems are scalable.
• Delay in data processing reduces.
• A failure of the main network will stop the entire communication.
• The language used to establish distributed systems is not well defined.
• These systems are expensive, complex, and not well understood.

Network Operating Systems

• A Network Operating System runs on a server, managing data, users, groups, security, applications, and other networking functions.
• The main goal is to allow shared file and printer access across multiple computers in a network, typically a local area network (LAN), private network, or other networks.
• Centralized servers are stable, with managed security.
• Upgrades to new hardware are easily integrated, and remote access is available.
• Disadvantages include the high cost of buying/running a server, dependency on a central location, and regular maintenance needs.
• A network OS uses software/protocols for computer network use, where users are aware of multiple machines.
• Distributed OS is like a centralized OS running on independent CPUs, where users are unaware of machine multiplicity.

Real-Time Operating System

• These OSs serve real-time systems.
• Response time, the time to process and respond to inputs, is very small.
• Maximum utilization of devices and system, thus more output from all the resources.
• Time assigned for shifting tasks in these systems are very less.
• For example, In older systems it takes about 10 micro seconds in shifting one task to another and in latest systems it takes 3 micro seconds.
• There is a focus on running applications, with less importance on applications in queue.
• Real time Operating Systems can also be used in embedded systems like in transport.
• These systems are often error free and have efficient memory allocation.
• Limits include few tasks running at once and a concentrated focus on avoiding errors.
• It use heavy and expensive system resources, and employ complex algorithms.
• Specific device drivers and interrupt signals are needed for quick response.
• It is not good to set thread priority with these systems as they are very less pron to switching tasks.