此为NachOs实验报告及源码，实验内容：

1. 研究code/shell 下的代码：

Nachos 所给的源代码的code/shell 目录下的源代码实现了一个shell，该shell 利用C/C++ 对Linux Shell 命令的调用支持( execl (SHELL, SHELL, "-c", exec_name,NULL) )实现了一个Shell 的Wrapper，使得一个函数(nachos_syscall.c 中的Exec(char*exec_name))可以实现所有的Linux Shell 命令。在Nachos 内核中，对具体的Shell命令实现可参考其实现方法，不要求对每个Shell 命令都去具体的实现。

2. 研究Nachos 的系统调用机制：

研究Nachos 的系统调用机制， 在Nachos 内核中实现关键系统调用， 以支持test/shell.c 通过交叉编译所生成程序的运行。通过分析test/shell.c 可知，这些关键系统调用包括：Write，Read，Exec，Join。假设test/shell.c 通过交叉编译所生成的程序为shell.noff，如果实现正确，则运行“nachos –x shell.noff”时会在Nachos 平台上为用户提供提供一个满足要求的Shell。-This is NachOs experimental reports and source code, experimental content:

A research code/shell code:

Source code under Nachos are to the source code code/the shell directory, a shell, the shell to use in C/C++ Linux Shell command the call to support (execl (the SHELL, SHELL-c ", exec_name, NULL)) a Shell Wrapper, make a function (nachos_syscall.c in Exec (char* exec_name)) can be achieved all the Linux shell command. Nachos kernel, specific Shell command can refer to the methods of their realization does not require each Shell commands to specific implementations.

2 Nachos system call mechanism:

Nachos system call mechanism of the study, critical system calls in Nachos kernel to support the test/shell.c generated by cross-compiling the program run. Test, analysis/shell.c shows these critical system calls include: Write, Read, Exec, Join. Assume that test, program/​ ​ the shell.c generated by the cross-compiler for shell.noff, if the realization of the right, then run th