Overview of IO input and output streams in C + + < two >

1 opening and closing of files

1.1 Defining a Stream object

Ifsteam iflie;//file input Stream object

Ifsteam iflie;//file output stream object

Fsteam iflie;//file input/output stream object

1.2 Open File

void Open (const unsigned char* filename,int mode,int accessfilebuf:opnprot)

Mode is the open way, the relevant tag as shown in (iOS)

　　　　

Attention:

(1) usually open way with | combine together

Ios::in|ios::out//Read-write mode open file

Ios::out|ios::binary//binary write mode open file

(2) Iftream: Default Ios::in

Ofstream: Default Ios::out|ios::trunc

FStream: Default Ios::in|ios::out|ios::app

2 State functions

EOF (): Read file reaches end true

Bad (): Error reading file returns True when I open a write that cannot be written

Fail: We enter a letter when we need to enter the shaping

Good: Returns False if any of the above functions are true

Clear ():

#include <iostream>#include<stdlib.h>using namespacestd;intMain () {intIntegerv; cout<<"before a bad input operation:"<<"\ cin.eof ():"<<cin.eof ()<<"\ Cin.fail ():"<<Cin.fail ()<<"\ncin.bad ():"<<Cin.bad ()<<"\ncin.good ()"<< Cin.good () <<Endl; CIN>> Integerv;//Control +d/zcout <<"After a bad input operation:"<<"\ cin.eof ():"<<cin.eof ()<<"\ Cin.fail ():"<<Cin.fail ()<<"\ncin.bad ():"<<Cin.bad ()<<"\ncin.good ()"<< Cin.good () <<Endl; System ("Pause"); return 1;}

3 (CIN) and (! CIN) Analysis

Whether the while (CIN) or if (CIN) is legal why? Customize a class and then define the object of the class, using the IF statement to determine that it is illegal. Indicates that the stream object has a convert function to convert a stream object into a type that the judgment statement can recognize

operator void* () const function in while (CIN) or if (CIN) implicit conversion bit void* type
BOOL operator! () const; The function is called in while (!cin) or if (!cin) to convert the stream object to a bool object
while (CIN)--->while (!cin.fail)
while (!cin)---->while (Cin.fail)

1 classA2 {3  Public:4 A () {}5~A () {}6     operator void*()Const7     {8cout <<"cast to void*";9         return(void*) This;Ten     } One     BOOL operator! ()Const A     { -cout <<"cast to bool"; -         return true; the     } - }; -  - intMain () + { - A; +     if(a) cout <<" First"<<Endl; A     if(!a) cout <<"Second"<<Endl; atSystem"Pause"); -     return 1; -}

4 file read and write operations

Overview of IO input and output streams in C + + < two >