COMPUTER SYSTEM STRUCTURE

1. Storage Structure

1.1. Main Memory(RAM), volatile storage, Secondary Memory(Hard Disk), can support many type of storage.

2. Storage Hierarchy

2.1. Storage System

2.1.1. organized in hierarchy is speed, cost, volatile.

2.2. Caching

2.2.1. Copying information into faster storage system.

2.2.2. Main memory can be viewed as a last cache for secondary storage.

3. Memory Protection

3.1. A way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems.

3.1.1. Base register-holds smallest legal physical memory address.

3.1.2. Limit register-contain size of the range.

4. CPU Protection

4.1. Every time the clock ticks, the counter is decremented.

4.2. When timer reaches the value 0, an interrupt occurs.

4.3. When timer interrupts, control transfers to the OS.

4.4. Load-timer is a privileged instruction.

5. Synchronous I/O Structure

5.1. Only one process that can be run a program at the same time.

6. Asynchronous I/O Structure

6.1. The program can run multiple process at the same time.

7. Dual-Mode Operation

7.1. User Mode

7.1.1. user program executes in user mode.

7.1.2. certain areas of memory are protected from user address.

7.1.3. certain instructions may not be executed.

7.2. Kernel Mode

7.2.1. monitor executes in kernel mode.

7.2.2. privileged instructions may be executed.

7.2.3. protected areas of memory may be accessed.