Operating System Concepts ABRAHAM SILBERSCHATZ PETER BAER GALVIN

Operating System Concepts 作業系統原理 著者 ABRAHAM SILBERSCHATZ PETER BAER GALVIN GREG GAGNE 1

1. 1 什麼是作業系統? n 一個電腦系統分成四個單元：硬體(Hardware)、作業系統(Operating System)、應用程式(Application Program)、使用者(User)。 CPU (Central Processing Unit)、 記憶體(Memory)、輸入/輸出裝置(I/O) 4

n 1. 2. 3 I/O 結構 Device Driver: (用在處理 小量資料) (用在處理大量資料) DMA: Direct Memory Access (Device與記憶體直接存取) Device SCSI: Small Computer Systems Interface 10

1. 8. 3 快取記憶體(caching) n Movement between levels of storage hierarchy can be explicit or implicit 作業系統 硬體功能 21

1. 8. 4 I/O 系統 n One purpose of OS is to hide peculiarities of hardware devices from the user n I/O subsystem responsible for q q q 記憶體管理構成要素包括緩衝(buffering)、快取和連線同時週邊作業。 通用裝置驅動程式(Driver)介面 特定硬體裝置驅動程式 22

1. 9 保護(Protection)與安全(Security) n n 電腦系統有許多使用者並且允許同時執行多個行程，則存取資料必須 井然有序。 為了這個目的，必須提供一些功能以確保檔案、記憶體區段、CPU和其 它的資源只能經由作業系統所認可並授權的行程適當地操作。 Protection – any mechanism for controlling access of processes or users to resources defined by the OS Security – defense of the system against internal and external attacks q n Huge range, including denial-of-service, worms, viruses, identity theft, theft of service Systems generally first distinguish among users, to determine who can do what q q User identities (user IDs, security IDs) include name and associated number, one per user User ID then associated with all files, processes of that user to determine access control Group identifier (group ID) allows set of users to be defined and controls managed, then also associated with each process, file Privilege escalation allows user to change to effective ID with more rights 23