System Calls

Library calls like printf or scanf, it searches through libraries. A system call is a mechanism that provides the interface between a process and the operating system.

• It is typically written in high level language (C, C++) and is accessed through Application Programming Interface (APIs) rather than direct system calls
  • Common APIs are Win32 for windows, POSIX API for POSIX-based systems (LINUX and Mac OS)
• System calls are the interface between an application program and the operating system.
• They provide a way for the application to request and carry out low-level services such as reading and writing files, creating processes, and allocating memory.
• The system calls are typically the most basic functions provided by the operating system, and higher-level libraries and APIs are built on top of them.

→ Sequence of systems calls to copy contents of one file to another

Device Status Table

Device-status table contains entry for each I/O device indicating its type, address, and state.

Direct Memory Access Structure

• Direct Memory Access (DMA) is a capability provided by some computer bus architectures that allows data to be sent directly from an attached device (such as a disk drive) to the memory on the computer's motherboard.
• Device controller transfers blocks of data from buffer storage directly to main memory without CPU intervention
• Only one interrupt is generated per block, rather than the one interrupt per byte

Cache

• Cache is a high-speed data storage layer which stores a subset of data, typically transient in nature, so that future requests for that data are served up faster than is possible by accessing the data's primary storage location.
• Copying information into faster storage system; main memory can be viewed as a cache for secondary storage

<aside> 💡 There are different algorithms to determine which data to put in cache

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Parallel Computing

• Parallel computing is a type of computing where multiple processors work together to solve a problem.
• It is designed to take advantage of multiple processors, cores, or computers to increase the speed of processing and to solve problems faster.
• In parallel computing, the problem is divided into smaller tasks that can be executed simultaneously by different processors, reducing the time it takes to solve the problem as a whole.

Distributed Computing (can’t confirm the info, this was written by notion’s AI)

• Distributed computing is a type of computing where multiple computers are connected together to solve a single problem.
• It involves the sharing of computing resources, data, and storage across multiple computers, enabling them to work together to solve a problem.
• In distributed computing, multiple computers can work on the same task in parallel, reducing the time it takes to complete the task.
• It is used in various applications, such as cloud computing, big data, and scientific computing.

Reliable Computing

To do one program on different processors, so that you get more reliable outcome, Ex: Setting coordinates for a satellite launch

Multiprocessing

A type of computing where multiple processors work together to solve a problem. It involves multiple CPUs or cores working together to perform tasks, with the goal of increasing processing power and improving system performance.

Symmetric Multiprocessing

• All processors have equal access to all system resources and work together to share the workload.
• Each processor can run any task at any time
• The operating system manages the distribution of tasks among the processors.
• Shared memory

Asymmetric Multiprocessing

• One processor is designated as the master and is responsible for managing the system, while the other processors are slaves and only perform tasks assigned by the master.
• The master processor has direct access to all system resources and communicates with the slave processors to coordinate the distribution of tasks.
• No shared memory

<aside> 💡 In general, SMP provides a more flexible and scalable solution for multiprocessing, while AMP is used in specialized systems where one processor needs to have more control over the system.

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A Dual-Core Design

• A dual-core system is a computer that has two processing cores integrated into a single physical processor.
• Each core is a separate processing unit that can execute instructions independently, allowing for multiple tasks to be processed simultaneously.
• A mode of operation in which two or more processors in a computer simultaneously process two or more different portions of the same program
• A bus which connects all the processors or cores in the memory (accessing the same memory)
• All the processors on the same device will have same time difference but on multiple devices, it will be different

Advantages of Dual-Core Systems

1. Increased Performance
2. Better Multitasking
3. Improved Power Efficiency
4. Improved Price-Performance Ratio

Disadvantages of Dual-Core Systems:

1. Limited Compatibility
2. Higher Complexity
3. Increased Cost (Relatively expensive)
4. Limited Scalability