00.1 (conspect) Challenges of OS and disadvantages of Assembler language

Operating system (OS)

is system software that manages computer hardware, software resources, and provides common services for computer programs (how to operate computer).

Functions:

• Separation
• Unification
• Account (fair consumption)

Resources:

• Operative memory(RAM) - Serves for time data storage with which the central processor works
• Processor time (measure of how much time the processor spends on any particular process, expressed in a ratio)
• Peripherals (внешние устройства такие как звуковая карта)

Multitasking

History:

• Batch mode (mode of skipping and simultaneous processing of user tasks - programs entered from external media or the terminal, taking into account their priorities and resources required by them) : Single Tasking
• Substituting multitasking (preemptive multitasking is a type of multitasking where the operating system decides to switch between tasks after a certain quantum of time has elapsed) : division of time, device lockdown
• Multiplayer mode : access sharing (including memory)

OS monolithic architecture:

• Kernel (The kernel is a computer program that is the core of a computer's operating system, with complete control over everything in the system) : implementation mechanisms (unification, separation, accounting «УРУ»)
• User space: logic of unification, separation, accounting and solving of user’s subtasks (for example, programming libraries - math libraries in c++/python);
• Computer applications: optional OS component for solving of the user task

C programming language

Disadvantages of assembler language:

• Call agreements of subtask
• Register planning / three types of variables - static, on stack and registers
• System call wrapper (numbers, various IT parameters, etc.)
• Arithmetic expressions
• Circuits and Conditional Operators
• Address arithmetic
• Compiling data types

What needs to be left behind:

• Actual memory/addressing model : The memory model corresponds to the hardware model (addresses)
• Scalar data types correspond to hardware
• The order of bytes in the machine word and its digit capacity