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看C++Primer的时候看到的,然后去百度了一下;

比较明白的解释:

1、区别在于:

只代表换行的转义字符
endl除了代表换行,还紧跟着清出缓冲槽

2、接下来我们看一下具体内容的辨析:
要明白
和endl的区别,首先要明白一个概念:
输出流。
目前输出流的类型很多,有对文件作为目标输出的,有对显示屏(Console间接输出)进行输出的。也有输出到其他抽象结构的。

cout的意思是console-output:控制台输出.
但是它的机制还远没有我们想的那么简单,<<后面跟着写什么就直接输出到屏幕什么?
不是这样的。

就拿cout<<"Hi,zw.
"<<endl;

来说,cout代表后面的内容输出到控制台的一个缓冲槽,而不是控制台(黑屏幕的那个).

缓冲槽在什么情况下会把缓冲槽的内容输出到控制台的【屏幕界面】呢?
当遇到endl或者其他fflush之类的命令或函数时,缓冲槽里的内容会按照顺序输出到控制台,再由控制台进行转意字符的识别打印。

endl和
的区别是:


在控制台里被翻译为【换行】
endl在控制台里也被翻译成【换行】

但endl还在缓冲槽这个部分有个功能:清槽,把缓冲槽里的内容输出到控制台。

为什么平时几乎没有任何区别呢?
因为缓冲槽即使不用endl,只要遇到另一行表达式,一般也会自动清槽。

只要程序不蹦,还是没什么区别的,万一程序崩溃,
可能会留在缓冲区里;

贴两段代码(及其汇编):

#include <iostream>
using namespace std;
int main()
{
	cout<<"a"<<endl;
	return 0; 
}
	.file	"3162643033743033731.cpp"
.lcomm __ZStL8__ioinit,1,1
	.def	___main;	.scl	2;	.type	32;	.endef
	.section .rdata,"dr"
LC0:
	.ascii "a"
	.text
	.globl	_main
	.def	_main;	.scl	2;	.type	32;	.endef
_main:
LFB971:
	.cfi_startproc
	leal	4(%esp), %ecx
	.cfi_def_cfa 1, 0
	andl	$-16, %esp
	pushl	-4(%ecx)
	pushl	%ebp
	.cfi_escape 0x10,0x5,0x2,0x75,0
	movl	%esp, %ebp
	pushl	%ecx
	.cfi_escape 0xf,0x3,0x75,0x7c,0x6
	subl	$20, %esp
	call	___main
	movl	$LC0, 4(%esp)
	movl	$__ZSt4cout, (%esp)
	call	__ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
	movl	$__ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, (%esp)
	movl	%eax, %ecx
	call	__ZNSolsEPFRSoS_E
	subl	$4, %esp
	movl	$0, %eax
	movl	-4(%ebp), %ecx
	.cfi_def_cfa 1, 0
	leave
	.cfi_restore 5
	leal	-4(%ecx), %esp
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
LFE971:
	.def	___tcf_0;	.scl	3;	.type	32;	.endef
___tcf_0:
LFB981:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	subl	$8, %esp
	movl	$__ZStL8__ioinit, %ecx
	call	__ZNSt8ios_base4InitD1Ev
	leave
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
LFE981:
	.def	__Z41__static_initialization_and_destruction_0ii;	.scl	3;	.type	32;	.endef
__Z41__static_initialization_and_destruction_0ii:
LFB980:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	subl	$24, %esp
	cmpl	$1, 8(%ebp)
	jne	L4
	cmpl	$65535, 12(%ebp)
	jne	L4
	movl	$__ZStL8__ioinit, %ecx
	call	__ZNSt8ios_base4InitC1Ev
	movl	$___tcf_0, (%esp)
	call	_atexit
L4:
	leave
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
LFE980:
	.def	__GLOBAL__sub_I_main;	.scl	3;	.type	32;	.endef
__GLOBAL__sub_I_main:
LFB982:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	subl	$24, %esp
	movl	$65535, 4(%esp)
	movl	$1, (%esp)
	call	__Z41__static_initialization_and_destruction_0ii
	leave
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
LFE982:
	.section	.ctors,"w"
	.align 4
	.long	__GLOBAL__sub_I_main
	.ident	"GCC: (GNU) 4.8.1"
	.def	__ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc;	.scl	2;	.type	32;	.endef
	.def	__ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_;	.scl	2;	.type	32;	.endef
	.def	__ZNSolsEPFRSoS_E;	.scl	2;	.type	32;	.endef
	.def	__ZNSt8ios_base4InitD1Ev;	.scl	2;	.type	32;	.endef
	.def	__ZNSt8ios_base4InitC1Ev;	.scl	2;	.type	32;	.endef
	.def	_atexit;	.scl	2;	.type	32;	.endef
#include <iostream>
using namespace std; 
int main()
{
	cout<<"a"<<"
";
	return 0; 
}
	.file	"3162643033743033732.cpp"
.lcomm __ZStL8__ioinit,1,1
	.def	___main;	.scl	2;	.type	32;	.endef
	.section .rdata,"dr"
LC0:
	.ascii "a"
LC1:
	.ascii "12"
	.text
	.globl	_main
	.def	_main;	.scl	2;	.type	32;	.endef
_main:
LFB971:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	andl	$-16, %esp
	subl	$16, %esp
	call	___main
	movl	$LC0, 4(%esp)
	movl	$__ZSt4cout, (%esp)
	call	__ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
	movl	$LC1, 4(%esp)
	movl	%eax, (%esp)
	call	__ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
	movl	$0, %eax
	leave
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
LFE971:
	.def	___tcf_0;	.scl	3;	.type	32;	.endef
___tcf_0:
LFB976:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	subl	$8, %esp
	movl	$__ZStL8__ioinit, %ecx
	call	__ZNSt8ios_base4InitD1Ev
	leave
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
LFE976:
	.def	__Z41__static_initialization_and_destruction_0ii;	.scl	3;	.type	32;	.endef
__Z41__static_initialization_and_destruction_0ii:
LFB975:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	subl	$24, %esp
	cmpl	$1, 8(%ebp)
	jne	L4
	cmpl	$65535, 12(%ebp)
	jne	L4
	movl	$__ZStL8__ioinit, %ecx
	call	__ZNSt8ios_base4InitC1Ev
	movl	$___tcf_0, (%esp)
	call	_atexit
L4:
	leave
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
LFE975:
	.def	__GLOBAL__sub_I_main;	.scl	3;	.type	32;	.endef
__GLOBAL__sub_I_main:
LFB977:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	subl	$24, %esp
	movl	$65535, 4(%esp)
	movl	$1, (%esp)
	call	__Z41__static_initialization_and_destruction_0ii
	leave
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
LFE977:
	.section	.ctors,"w"
	.align 4
	.long	__GLOBAL__sub_I_main
	.ident	"GCC: (GNU) 4.8.1"
	.def	__ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc;	.scl	2;	.type	32;	.endef
	.def	__ZNSt8ios_base4InitD1Ev;	.scl	2;	.type	32;	.endef
	.def	__ZNSt8ios_base4InitC1Ev;	.scl	2;	.type	32;	.endef
	.def	_atexit;	.scl	2;	.type	32;	.endef

本弱汇编还在学= = 所以很多看不懂=- =~

等能看懂了,再回来研究研究