(1)What will happen if you execute following program?
#include<stdio.h>
int main(){
unsigned char c;
FILE *fp;
fp=fopen("test.text","r");
while((c=fgetc(fp))!=EOF)
printf("%c",c);
fclose(fp);
return 0;
}
//test.txt
I am reading file handling in
cquestionbank.blogspot.com
Output:
It will print the content of file
text.txt but it will enter in infinite loop because macro EOF means -1 and at
the end of file function fgetc will also return -1 but c can store only unsigned char.
It will store any positive number according to rule of cyclic nature of data
type. Hence condition will be always true.
(2)What will happen if you execute following program?
#include<stdio.h>
int main(){
char *str;
FILE *fp;
fp=fopen("c:\tc\bin\test.txt","r");
while(fgets(str,15,fp)!=NULL)
printf("%s",str);
fclose(fp);
return 0;
}
//test.txt
I am reading file handling in
cquestionbank.blogspot.com
Output: It will print NULL.
Explanation: As we know \ has
special meaning in c programming. To store \ in a string data type there
requirements of two forward slash i.e. \\. In this case fopen function will return NULL value due to wrong URL.
Right way to write that URL is:
c:\\tc\\bin\\test.txt
(3)What will be output of following
program?
#include<stdio.h>
int main(){
FILE *fp;
char *str;
fp=fopen("c:\\tc\\bin\\world.txt","r");
while(fgets(str,5,fp)!=NULL)
puts(str);
fclose(fp);
return 0;
}
//world .txt
Who are you?
Output: Who a
Explanation: It will
print only first five character of including blank space of file world.txt
(4)What will happen if you execute
following program?
#include<stdio.h>
int main(){
FILE *fp1,*fp2;
fp1=fopen("day.text","r");
fp2=fopen("night.txt","r");
fclose(fp1,fp2);
return 0;
}
Output: Compiler error
Explanation: We cannot close
more than one file using fclose function.
(5)What will be output of following
program?
#include<stdio.h>
int main(){
fprintf(stdout,"cquestionbank");
return 0;
}
Output: cqestionbank
Explanation: stdout means
standard output.
(6)What will be output of following
program?
#include<stdio.h>{
char *str="i know c .";
while(*str)
{
putc(*str,stdout);
fputchar(*str);
printf("%c",*str);
str++;
}
return 0;
}
Output: iii kkknnnooowww ccc ...
Explanation: We are using
three functions to print or write in stream.
1. putc is
function it can print one character on any stream. Since here stream
is stdout so it will print on standard output screen.
2. fputchar function can
print one character on standard output screen.
3. printf function can
print one character on standard output screen.
(7)What will happen if you execute
following program?
#include<stdio.h>
int main(){
char c;
FILE *fp;
fp=fopen("d:\\rootro~1\\raja.txt","r");
while((c=fgetc(fp))!=EOF)
printf("%c",c);
fclose(fp);
return 0;
}
Output: It will print contain
of file D:/root root/raja.txt
Explanation: If name
folder or file is more than eight characters then in URL write on first six
character and add ~1 at the end of name of folder or file.
For example:
mypicture: mypict~1
filehandling: fileha~1
If file or folder name contain in
any blank space then remove that blank space
For example:
my photo: myphoto
program files: program~1
If two file became same then use ~2
and so on.
(8)What will be output of following
program?
#include<stdio.h>
int main(){
char c;
FILE *fp;
fp=fopen("d:\\rootro~1\\raja.txt","r");
while((c=fgetc(fp))!=EOF){
printf("\n%c",c);
printf("--%d",fp->level);
}
fclose(fp);
return 0;
}
//raja.txt
I love world
Output:
I--11
--10
l--9
o--8
v--7
e--6
--5
w--4
o--3
r--2
l--1
d—0
Explanation:
FILE pointer is struct data type which has been
defined in standard library stdio.h. It has been defined in stdio.h as
typedef struct{
short level;
unsigned flags;
char fd;
unsigned char hold;
short bsize;
unsigned char *buffer,
*curp;
unsigned istemp;
short token;
} FILE;
Here level indicates how many more
character have to read at particular instant.
File raja.text has total 12 character including blank space have
to read at initial moment as it read raja.txt number of character
also decrease gradually which have to read.
(9)What will be output of following
program?
#include<stdio.h>
int main(){
char c;
FILE *fp;
fp=fopen("test.txt","r");
printf("\n %x",fp->flags);
fp=fopen("test.txt","rb+");
printf("\n %x",fp->flags);
fclose(fp);
return 0;
}
Output: 5 47
Explanation:
In stdio.h there are flag status
macros which are:
NAME Meaning Value
(In hexadecimal)
_F_RDWR Read and
write 0X0003
_F_READ Read-only
file 0X0001
_F_WRIT Write-only
file 0X0002
_F_BUF Malloc'ed buffer
data 0X0004
_F_LBUF Line-buffered
file 0X0008
_F_ERR Error
indicator 0X0010
_F_EOF EOF
indicator 0X0020
_F_BIN Binary file
indicator 0X0040
_F_IN Data is
incoming 0X0080
_F_OUT Data is
outgoing 0X00100
_F_TERM File is a
terminal 0X00200
In statement fp=fopen ("test.txt","r");
Mode of open file is read only.
So fp->flags=read only + buffer
data=_F_READ+_F_BUF=1+4=5
fp=fopen("test.txt","rb+");
Mode of open file is
read and writes in binary data format.
So fp->flags=read and write+ buffer data+
Binary file
=_F_RDWR+_F_BUF+_F_BIN=3+4+40=47
Note:
FILE pointer is struct data type which has been
defined in standard library stdio.h. This data type points to a stream or a
null value. It has been defined in stdio.h as
typedef struct{
short level;
unsigned flags;
char fd;
unsigned char hold;
short bsize;
unsigned char *buffer,
*curp;
unsigned istemp;
short token;
} FILE
;
Here flags tell current status of file.
(10)What will be output of following
program?
#include<stdio.h>
int main(){
char *str;
FILE *fp;
fp=fopen("test.txt","r");
fgets(str,12,fp);
printf("%s",str);
fclose(fp);
return 0;
}
//test.txt
Save water every day.
Output: Save water
Explanation: It will print only
first 12 character including blank space from file test.txt
(11)What will be output of following
program?
#include<stdio.h>
int main(){
fprintf(&_streams[1],"www.cquestionbank.blogspot.com");
return 0;
}
Output: www.cquestionbank.blogspot.com
Explanation:
Array &_streams[1] is equivalent
to stdout which has been defined in stdio.h
So fprintf(stdout,"www.cquestionbank.blogspot.com");
will print the string at standard output.
Another streams array which has been
defined in stdio.h as
#define stdin &_streams[0]
#define stdout &_streams[1]
#define stderr &_streams[2]
#define stdaux &_streams[3]
#define stdprn &_streams[4]
(12)What will be output of following
program?
#include<stdio.h>
int main(){
printf("%d",EOF);
return 0;
}
Output: -1
Explanation: EOF is macro which
has been defined in stdio.h and it is equivalent to -1
(13)What will be output of following
program?
//test.c
#include<stdio.h>
int main(){
++EOF;
printf("%d",EOF);
return 0;
}
Output: Compiler error
Explanation:
EOF is macro which has been defined
in stdio.h and it is equivalent to -1. Since #define is token pasting operator
which process before the start of actual compilation and create a intermediate
as: Write in command prompt
cpp
test.c //create intermediate file
type
test.i //to
view intermediate file
So it replaces EOF by -1
And statement ++ (-1) is wrong in c
language since we cannot increment constant value.
(14)What will be output of following
program?
#include<stdio.h>
int main(){
char c;
FILE *fp;
fp=fopen("myfile.txt","r+");
fprintf(fp,"you know");
fclose(fp);
fp=fopen("myfile.txt","r");
while((c=fgetc(fp))!=EOF)
printf("%c",c);
fclose(fp);
return 0;
}
//myfile.txt
I am reading file handling from
cquestionbank.blogspot.com
Output: you knowding file handling from
cquestionbank.blogspot.com
Explanation:
mode r+ allow us to read and write
on file and it doesn’t truncate (delete) the content of file but new
content but it starts writing from beginning of file so it will
override the content of file.
(15)What will be output of following
program?
#include<stdio.h>
int main(){
char c;
FILE *fp;
fp=fopen("myfile.txt","w+");
fprintf(fp,"you know");
fclose(fp);
fp=fopen("myfile.txt","r");
while((c=fgetc(fp))!=EOF)
printf("%c",c);
fclose(fp);
return 0;
}
//myfile.txt
I am reading file handling from
cquestionbank.blogspot.com
Output: you know
Explanation:
Mode w+ allow us read and write on
file but it truncates (delete) the previous content of file.
(16)What will be output of following
program?
#include<stdio.h>
int main(){
char c;
FILE *fp;
fp=fopen("myfile.txt","w");
while((c=fgetc(fp))!=EOF)
printf("%c",c);
fclose(fp);
return 0;
}
//myfile.txt
I am reading file handling from
cquestionbank.blogspot.com
Output: nothing
Explanation:
Mode w allow us write on the file
but we cannot read the content and it truncates (delete) the content of file.
So content of file will be also deleted.
(17)What will be output of following
program?
#include<stdio.h>
int main(){
char c;
FILE *fp;
fp=fopen("myfile.txt","a");
while((c=fgetc(fp))!=EOF)
printf("%c",c);
fclose(fp);
return 0;
}
//myfile.txt
I am reading file handling from cquestionbank.blogspot.com
Output: NULL
Explanation:
Mode a allow us write on file but we
cannot read the content and it doesn’t truncate (delete) the content of file.
So content of file will not change.
(18)What will be output of following
program?
#include<stdio.h>
int main(){
char c;
FILE *fp;
fp=fopen("myfile.txt","a+");
fprintf(fp,"you know");
fclose(fp);
fp=fopen("myfile.txt","r");
while((c=fgetc(fp))!=EOF)
printf("%c",c);
fclose(fp);
return 0;
}
//myfile.txt
I am reading file handling from
cquestionbank.blogspot.com
Output: I am reading file handling from
cquestionbank.blogspot.comyou know
Explanation:
Mode a+ means we can read and write
on file but when we will write on file it will append at the end content and it
doesn’t truncate the content of file.
(19)What is difference between file
opening mode rb and rb+?
Answer:
Mode rb means
combination of mode r and mode b while mode rb+ means combination of mode r+
and mode b.
4 comments:
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