Operating System Architecture: Core Management Functions

Level 1: Processor Management

Objectives

• Share CPU between processes without blocking the system.

Functions

• Initial startup synchronization between processes.
• CPU switching.
• Memory management.
• Interrupt management.

Level 2: Memory Management

Functions

• Allocation and release of memory.
• Control of access violations.

Level 3: Process Management

Objectives

• High-level process management.

Functions

• Creation and destruction of processes.
• Message exchange between processes.
• Detention and booting of processes.

Level 4: Device Management

Objectives

• Manage I/O based on existing process devices.

Functions

• I/O creation.
• Allocation and release of I/O devices.
• I/O scheduling.

Level 5: Information Management

Objectives

• Manage logical namespace, storage, and information protection.

Functions

• Creation and destruction of files and directories.
• Opening and closing files.
• Reading and writing files.
• Access protection.

Program Execution and Process Lifecycle

When a program is executed, it is loaded into memory by the loader. The dispatcher prepares the execution:

• BCP Creation: Creates the Process Control Block.
• Identification: Assigns a PID and a base priority.
• Resource Allocation: Assigns all necessary resources (except CPU).
• System Integration: Inserts the process into the system process table and loads it into virtual memory.
• State Transition: Changes the state to 'ready' and inserts it into the ready queue.

The Scheduler

The scheduler decides which process to execute based on dynamic priorities. To prevent starvation of low-priority processes, the planner:

• Reprioritizes processes in the CPU queue.
• Selects the process with the highest priority.
• Updates the process status field to 'execution'.
• Calls the context switch routine.

Each process is assigned a number of quantums, which may be static or dynamic depending on priority. Upon completion, the process calls the interrupt manager. Major interruptions include execution time limits, I/O requests, or errors.