Operating Systems and Programming Terminology

Programming Terminology

• Software consists of programs that carry out tasks, while a program is a sequence of instructions.
• Programs reside in main memory during execution but are stored on secondary storage devices like disks, drums, or tapes.
• The operating system (OS) creates an environment for executing programs, such as compilers.

Operating System Terminology

• A job comprises multiple activities submitted by a user to the OS.
• Jobs can be broken down into sequential units known as job steps.
• Once a job is accepted, the OS generates processes that run concurrently.
• Address spaces include I/O processes and CPU processes.

Multiprogramming

• Systems may run several processes simultaneously.
• Two main execution states exist: user state and supervisor state.

Operating System Resource Management

• The OS functions as a resource manager for memory, processors, and peripheral devices.
• It resolves conflicts for resource allocation to ensure fair and efficient operations.
• The OS maintains a status log for each resource and makes decisions on allocation and deallocation.

I/O Programming

• Early computer systems consisted of the CPU, main storage, and I/O devices.
• I/O instructions managed device operations one at a time, revealing speed disparities between the CPU and I/O devices.
• I/O processors (or channels) enable data flow between I/O devices and main memory.

Types of I/O Channels

• Simple and complex I/O channels can service multiple devices; up to 256 devices can connect to one channel.
• Selector channels attend to one high-speed device at a time.
• Multiplexor channels serve multiple slow devices simultaneously.

I/O Programming Concepts

• The CPU starts, tests, and halts I/O operations using designated instructions and communicates with the I/O processor via interrupts.
• Status codes indicate whether a device is busy, operational, or ready.

Buffering Techniques

• Single buffering uses one area for reading while the CPU processes data, often leading to idle time for either the CPU or the I/O channel.
• Double buffering accelerates card processing by reading into one buffer while another is printed.

Interrupt Structure and Processing

• An interrupt signifies an asynchronous event and saves the CPU's state for later resumption.
• The Program Status Word (PSW) preserves the CPU's condition during interrupts, influencing instruction sequence and system status.
• Interrupts classified into five types: I/O, program, supervisor call, external, and machine-check.

Memory Management

• Memory management is crucial for handling primary memory within the OS.
• Functions include tracking memory usage, deciding process allocations, and memory allocation and deallocation.

Memory Management Techniques

• Includes various strategies: contiguous, partitioned, paged, demand-paged, segmented, and combined segmented/demand-paged methods.
• Swapping and overlays are additional memory management techniques implemented for efficiency.

Contiguous vs Non-Contiguous Storage Allocation

• Contiguous allocation requires programs to occupy single memory blocks.
• Non-contiguous allocation permits programs to be divided into blocks scattered throughout memory.

Single Contiguous Allocation

• Simplistic memory management divides memory into OS and user process partitions.
• No specialized hardware is required, but it does not support multiprogramming.

Boundary Register

• The boundary register holds the highest address used by the OS, ensuring user processes do not access OS memory.
• Violations lead to interrupts, terminating the offending job with an error message.

This quiz covers essential concepts related to operating systems and programming. Topics include the relationship between programs and software, job management, multiprogramming, and resource management within an OS. Test your knowledge of how these elements interact in a computing environment.