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**Operatsion Tizimda Oqimlarni (Thread) Boshqarish Modellari**
**Kirish**
Oqimlar (threads) operatsion tizimlarning asosiy tarkibiy qismlaridan biridir. Ular dasturlarni parallel ishlash imkonini beradi, bu esa tizimning samaradorligini oshiradi. Ushbu maqolada oqimlarni boshqarish modellari, ularning turlari va ishlash prinsiplari ko‘rib chiqiladi. Oqimlarni samarali boshqarish operatsion tizimlar uchun juda muhimdir, chunki bu tizimning umumiy ishlashiga katta ta’sir ko‘rsatadi.
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**1. Oqimlarni Boshqarishning Asosiy Konseptsiyalari**
1.1 **Oqim (Thread) Nima?**
Oqim — bu protsess ichida mustaqil ravishda ishlaydigan ijro etish birligi. Har bir oqim o‘zining stack, register va programm counter (PC) kabi resurslariga ega bo‘ladi. Oqimlar ko‘pincha protsesslar ichida birgalikda ishlaydi, ammo ular o‘zaro mustaqil bo‘ladi.
1.2 **Oqimlar va Protsesslar: Farqlar**
- **Protsess** — bu operatsion tizimdagi mustaqil ijro etish birligi bo‘lib, u o‘zining kod, ma’lumot va boshqa resurslar bilan birga ishlaydi.
- **Oqim** — bu protsess ichidagi ijro etish birligi bo‘lib, u protsessning resurslarini birgalikda ishlatadi.
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**2. Oqimlarni Boshqarish Modellari**
2.1 **Boshqaruv Modellarining Turlari**
Oqimlarni boshqarish uchun bir nechta model mavjud bo‘lib, ular orasida eng keng tarqalganlari quyidagilar:
- **Mulk (Ownership) Modeli**
Har bir oqimga o‘z xususiy ma’lumotlar maydoni beriladi va ular bir-biridan mustaqil ishlaydi. Bu modelda har bir oqim o‘zining stack va boshqa resurslarini boshqaradi.
- **Qo‘shma (Cooperative) Modeli**
Oqimlar o‘zaro ishlashni tartibga solishda hamkorlik qiladi. Bu modelda oqimlar resurslarni bo‘lishib ishlatadi va sinxronizatsiyaga ehtiyoj seziladi.
- **Mustaqil (Preemptive) Modeli**
Operatsion tizim oqimlarni nazorat qilib, ularga vaqtni taqsimlaydi. Bu modelda oqimlar operatsion tizim tomonidan boshqariladi va har bir oqim uchun vaqt belgilanadi.
2.2 **Mulk Modelining Afzalliklari va Kamchiliklari**
- **Afzalliklari:**
- Samaradorlik va tezkorlik yuqori bo‘ladi.
- Har bir oqim o‘z resurslarini boshqarishi mumkin.
- **Kamchiliklari:**
- Boshqaruv qiyin bo‘ladi, ayniqsa ko‘p oqimli tizimlarda.
- Xatolik xavfi yuqori, chunki har bir oqim o‘z resurslarini boshqarishi kerak.
2.3 **Qo‘shma Modelning Xususiyatlari**
- **Afzalliklari:**
- Resurslarni bo‘lishib ishlatish imkoniyati mavjud.
- Sinxronizatsiya orqali oqimlar bir-birini to‘sib qo‘ymasligi mumkin.
- **Kamchiliklari:**
- Sinxronizatsiya talab etiladi, bu esa murakkablikni oshiradi.
- Oqimlar bir-biriga bog‘liq bo‘lishi mumkin.
2.4 **Mustaqil Modelning Afzalliklari**
- **Afzalliklari:**
- Operatsion tizim oqimlarni avtomatik ravishda boshqaradi.
- Xatoliklarni kamaytiradi, chunki tizim tomonidan nazorat qilinadi.
- **Kamchiliklari:**
- Boshqaruvning murakkabligi ortadi, chunki tizim oqimlarni doimiy ravishda nazorat qiladi.
- Samaradorlik ba’zan pasayishi mumkin, chunki har bir oqimga belgilangan vaqt ajratiladi.
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**3. Oqimlarni Boshqarishdagi Eng Yangi Yondashuvlar**
3.1 **Yuqori Darajadagi Boshqaruv Tizimlari**
Oqimlarni boshqarish uchun zamonaviy yuqori darajadagi yondashuvlar mavjud. Bu yondashuvlar oqimlarni boshqarishni soddalashtiradi va samaradorligini oshiradi. Misollar:
- `pthread` — C va C++ dasturlash tillari uchun oqimlarni boshqarish kutubxonasi.
- `OpenMP` — Parallel dasturlash uchun ochiq standart bo‘lib, C, C++ va Fortran tillari uchun mo‘ljallangan.
- `MPI` — Xabar almashish interfeysi bo‘lib, parallel dasturlash uchun keng qo‘llaniladi.
3.2 **Sinhronizatsiya Texnikalari**
Oqimlarni boshqarishda sinhronizatsiya juda muhim. Quyidagi sinhronizatsiya texnikalari keng qo‘llaniladi:
- **Semaforlar** — Bu sinhronizatsiya primitivlari bo‘lib, oqimlar o‘rtasida resurslarni boshqarish uchun ishlatiladi.
- **Monitors** — Bu texnika oqimlarni sinxronizatsiya qilishda ishlatiladi va ko‘pincha obyektga yo‘naltirilgan dasturlash tillarida qo‘llaniladi.
- **Qayd etish (Mutexes)** — Bu texnika yordamida oqimlar o‘rtasida to‘siqlar yaratilib, sinxronizatsiya amalga oshiriladi.
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**4. Tadqiqotlar va Amaliyot**
4.1 **Tadqiqotlar Natijalari**
Turli oqim boshqaruv modellari samaradorligi, ishlash tezligi va xatolik darajasi bo‘yicha tadqiqotlar olib borilgan. Natijalar shuni ko‘rsatadiki, har bir modelning o‘z afzallik va kamchiliklari mavjud bo‘lib, ularni qo‘llash jarayonida turli omillar hisobga olinishi kerak.
4.2 **Amaliyot Misollari**
Quyida oqimlarni boshqarishning turli metodlari uchun kod misollari keltiriladi:
```c
// pthread misoli
#include
#include
void *print_message(void *ptr) {
char *message;
message = (char *)ptr;
printf("%s \n", message);
return NULL;
}
int main() {
pthread_t thread1, thread2;
char *message1 = "Thread 1";
char *message2 = "Thread 2";
pthread_create(&thread1, NULL, print_message, (void *)message1);
pthread_create(&thread2, NULL, print_message, (void *)message2);
pthread_join(thread1, NULL);
pthread_join(thread2, NULL);
return 0;
}
```
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**Xulosa**
Operatsion tizimlarda oqimlarni boshqarish tizimlari zamonaviy dasturiy ta’minotning ajralmas qismidir. Ularning samaradorligi va ishonchliligi tizimning umumiy ishlashiga katta ta’sir ko‘rsatadi. Shu sababli, oqimlarni boshqarish modellari va ularni optimallashtirish muhim ahamiyat kasb etadi.
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**Manbalar**
- Tanenbaum, A.S., & Bos, H. (2014). Modern Operating Systems. Pearson.
- Silberschatz, A., Galvin, P.B., & Gagne, G. (2018). Operating System Concepts. Wiley.
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### Topic 7: Computer Input-Output Systems
#### Plan:
1. Organization of Input-Output Systems
2. Input-Output Control Tools, Channels, and Processors
3. Input-Output Modules, Ports, and Their Functions
### Organization of Input-Output Systems
#### BIOS and Its Functions
BIOS (Basic Input/Output System) is a program written on a computer’s motherboard's ROM (Read-Only Memory) or EEPROM (Electrically Erasable Programmable Read-Only Memory) chip. When the computer is turned on, BIOS performs initial hardware checks (POST), loads the Master Boot Record (MBR), and hands control over to the operating system. BIOS handles input-output device requests from the operating system.
#### POST and MBR
- **POST (Power-On Self-Test)**: When the computer is turned on, the BIOS program performs a self-test sequence to check the system components one by one.
- **MBR (Master Boot Record)**: This is the first physical sector of a hard disk or other storage device, containing the partition table and a small amount of executable code. Its main purpose is to identify which partition to load the operating system from.
#### Functions of BIOS
- Activate the computer and bring all elements to their initial state
- Perform an initial check of computer hardware (POST-test)
- Distribute system resources
- Register and configure PCI devices
- Perform the initial load of the operating system (bootmgr)
- Ensure compatibility between devices
- Manage power supply, including shutting down and putting the computer into sleep mode
#### Proper BIOS Configuration
Properly configuring BIOS significantly affects computer performance. BIOS programs are developed by companies like American Megatrends (AMI), Award Software, and Phoenix Technologies. Different motherboards use different BIOS types, so a single manual is not possible, but the basic principles remain the same.
#### BIOS vs. Modern Boot Managers
NTLDR (NT Loader) assists in booting the Windows XP operating system. In systems released after Windows XP, BOOTMGR and winload.exe replace NTLDR. While BIOS handles various tasks, in modern systems, some of these tasks are performed by UEFI (Unified Extensible Firmware Interface).
### Additional Information
#### UEFI and Its Advantages
In modern systems, UEFI replaces BIOS and offers the following advantages:
- Enhanced security features, including Secure Boot, which ensures that only trusted software from the manufacturer is loaded.
- Faster boot times
- Support for larger hard drives (greater than 2 TB)
#### BIOS Security
- **Secure Boot**: A UEFI feature that ensures only trusted software from the manufacturer is loaded during the boot process.
- **BIOS Passwords**: Used to prevent unauthorized changes to BIOS settings.
#### Updating BIOS
Updating BIOS:
- Can fix bugs, add support for new hardware, and improve system stability.
- Is risky and should be performed carefully, following the manufacturer’s instructions.
### Conclusion
This document provides a comprehensive overview of computer input-output systems, specifically focusing on BIOS and its components. The information is technically accurate and reliable. Modern systems also include features like UEFI and Secure Boot, which extend and enhance traditional BIOS functionalities. Proper BIOS configuration and updates have a significant impact on system performance.
Yes, the structure of I/O in operating systems is a valid and important topic. It refers to the way in which I/O operations are organized and managed within the OS. Here is some information that you can include in your independent work to explain the structure of I/O:
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**Structure of I/O in Operating Systems**
The I/O system in an operating system is structured to efficiently manage the flow of data between the computer and its peripherals. The structure can be broken down into several key components and layers:
**1. Hardware Layer**
- **I/O Devices:** Physical components like keyboards, mice, printers, disk drives, network interfaces, etc.
- **Device Controllers:** Hardware components that connect the I/O devices to the computer and manage the data exchange between the device and the system bus.
**2. Device Drivers**
- Device drivers are specialized software programs that control specific I/O devices. They provide an interface between the operating system and the hardware, translating OS commands into device-specific instructions.
- **Functions of Device Drivers:**
- **Initialization:** Preparing the device for operation.
- **Data Transfer:** Managing the flow of data to and from the device.
- **Control Operations:** Sending control commands to the device.
- **Error Handling:** Detecting and managing errors that occur during device operations.
**3. Interrupt Handlers**
- Interrupt handlers are routines that manage interrupts sent by I/O devices. When a device needs attention (e.g., it has completed a data transfer), it sends an interrupt signal to the CPU.
- The OS pauses its current tasks to service the interrupt, ensuring timely processing of I/O operations.
**4. I/O Scheduling**
- I/O scheduling determines the order in which I/O requests are processed. This is important for optimizing performance and ensuring fairness.
- Common scheduling algorithms include First-Come-First-Served (FCFS), Shortest Seek Time First (SSTF), and Elevator (SCAN).
**5. Buffering and Caching**
- **Buffering:** Temporarily storing data in memory while it is being transferred between the computer and an I/O device. This helps to cope with speed differences between the CPU and I/O devices.
- **Caching:** Storing frequently accessed data in a faster storage medium to reduce access times.
**6. I/O Subsystem**
- The I/O subsystem is part of the OS that manages I/O operations. It includes:
- **System Call Interface:** Provides a way for user applications to request I/O operations from the OS.
- **I/O System Calls:** Functions that handle I/O operations, such as read, write, open, and close.
- **File System:** Manages the storage and retrieval of data on disk drives.
- **Network Subsystem:** Manages network communication and data transfer.
**7. Direct Memory Access (DMA)**
- DMA is a technique that allows certain hardware subsystems to access the main system memory independently of the CPU. This speeds up data transfers and frees up the CPU for other tasks.
**Diagram: Simplified I/O Structure**
```
+-----------------+
| User Space |
| (Applications)|
+-----------------+
|
V
+-----------------+
| System Call |
| Interface |
+-----------------+
|
V
+-----------------+
| I/O Subsystem |
| (OS Kernel) |
| - Device Drivers|
| - I/O Scheduler |
| - Buffer Cache |
+-----------------+
|
V
+-----------------+
| Hardware Layer |
| - Device Ctrlrs |
| - I/O Devices |
+-----------------+
```
**Conclusion**
Understanding the structure of I/O in operating systems is essential for comprehending how data flows between the computer and its peripherals. This structure, encompassing hardware, device drivers, interrupt handlers, I/O scheduling, buffering, caching, and DMA, is designed to optimize performance, ensure data integrity, and maintain efficient resource allocation.
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You can include this explanation in your independent work to cover the structure of I/O in operating systems. If you need more details or further clarification, feel free to ask!
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