Study Guide to Accompany Operating Systems （学习指南伴随操作系统）.pdfVIP

Study Guide to Accompany Operating Systems Concepts 9th Ed by Silberschatz, Galvin and Gagne By Andrew DeNicola, BU ECE Class of 2012 Figures Copyright © John Wiley Sons 2012 Ch.1 - Introduction • An OS is a program that acts as an intermediary between a user of a computer and the computer hardware • Goals: Execute user programs, make the comp. system easy to use, utilize hardware efficiently • Computer system: Hardware ↔ OS ↔ Applications ↔ Users (↔ = uses) • OS is: ◦ Resource allocator: decides between conflicting requests for efficient and fair resource use ◦ Control program: controls execution of programs to prevent errors and improper use of computer • Kernel: the one program running at all times on the computer • Bootstrap program: loaded at power-up or reboot ◦ Stored in ROM or EPROM (known as firmware), Initializes all aspects of system, loads OS kernel and starts execution • I/O and CPU can execute concurrently • Device controllers inform CPU that it is finished w/ operation by causing an interrupt ◦ Interrupt transfers control to the interrupt service routine generally, through the interrupt vector, which contains the addresses of all the service routines ◦ Incoming interrupts are disabled while another interrupt is being processed ◦ Trap is a software generated interrupt caused by error or user request ◦ OS determines which type of interrupt has occurred by polling or the vectored interrupt system • System call: request to the operating system to allow user to wait for I/O completion • Device-status table: contains entry for each I/O device indicating its type, address, and state ◦ OS indexes into the I/O device table to determine device s