现代操作系统全套配套课件4eTanenbaumPPT及教学资料Chapter01-Introduction.ppt

Processes (1) Key concept in all operating systems Definition: a program in execution Process is associated with an address space Also associated with set of resources Process can be thought of as a container Holds all information needed to run program Tanenbaum Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Processes (2) Figure 1-13. A process tree. Process A created two child processes, B and C. Process B created three child processes, D, E, and F. Tanenbaum Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Files (1) Figure 1-14. A file system for a university department. Tanenbaum Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Files (2) Figure 1-15. (a) Before mounting, the files on the CD-ROM are not accessible. (b) After mounting, they are part of the file hierarchy. Tanenbaum Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Files (3) Figure 1-16. Two processes connected by a pipe. Tanenbaum Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. Ontogeny Recapitulates Phylogeny Each new “species” of computer Goes through same development as “ancestors” Consequence of impermanence Text often looks at “obsolete” concepts Changes in technology may bring them back Happens with large memory, protection hardware, disks, virtual memory Tanenbaum Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. System Calls (1) Figure 1-17. The 11 steps in making the system call read(fd, buffer, nbytes). Tanenbaum Bo, Modern Operating Systems:4th ed., (c) 2013 Prentice-Hall, Inc. All rights reserved. System Calls (2) Figure 1-18. Some of the major POSIX system calls. The return code s is ?1 if an error has occurred. The return codes are as follows: pid is a process id, fd is a file descriptor, n is a byte count, position is an offset