minux的源代码,一个非常小的操作系统

				/*
				 * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
				 * See the copyright notice in the ACK home directory, in the file "Copyright".
				 */
				/* $Header: atol.c,v 1.3 90/05/22 10:48:12 ceriel Exp $ */
				
				#include	
				#include	
				
				/* We do not use strtol here for backwards compatibility in behaviour on
				   overflow.
				*/
				long
				atol(register const char *nptr)
				{
					long total = 0;
					int minus = 0;
				
					while (isspace(*nptr)) nptr++;
					if (*nptr == '+') nptr++;
					else if (*nptr == '-') {
						minus = 1;
						nptr++;
					}
					while (isdigit(*nptr)) {
						total *= 10;
						total += (*nptr++ - '0');
					}
					return minus ? -total : total;
				}