General Computer

C Programming Input / Output Online Test, C Programming Mock Quiz

By Raju Choudhary On Feb 13, 2019

C Programming Input / Output Online Test

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C Programming Input / Output Online Test. C Programming Question and Answers in English. C Programming Input / Output Online mock test paper is free for all students and Very Helpful for Exam Preparation. C Programming Input / Output Online Quiz. C Programming Online Mock test for Input / Output Topic. Here we are providing C Programming Input / Output Online Test Series in English. Check C Programming Mock Test Series 2019-2019.

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Question 1 of 30

1. Question
In a file contains the line “I am a boy\r\n” then on reading this line into the array str using fgets(). What will str contain?
- "I am a boy\r\n\0"
- "I am a boy\r\0"
- "I am a boy\n\0"
- "I am a boy"
Correct

Declaration: char *fgets(char *s, int n, FILE *stream);

fgets reads characters from stream into the string s. It stops when it reads either n – 1 characters or a newline character, whichever comes first.

Therefore, the string str contain “I am a boy\n\0”

Incorrect

Declaration: char *fgets(char *s, int n, FILE *stream);

fgets reads characters from stream into the string s. It stops when it reads either n – 1 characters or a newline character, whichever comes first.

Therefore, the string str contain “I am a boy\n\0”

Question 2 of 30

2. Question

What is the purpose of “rb” in fopen() function used below in the code?

FILE *fp;
fp = fopen("source.txt", "rb");

open "source.txt" in binary mode for reading
open "source.txt" in binary mode for reading and writing
Create a new file "source.txt" for reading and writing
None of above

Correct

The file source.txt will be opened in the binary mode.

Incorrect

The file source.txt will be opened in the binary mode.

Question 3 of 30

3. Question

What does fp point to in the program ?

#include

int main()
{
    FILE *fp;
    fp=fopen("trial", "r");
    return 0;
}

The first character in the file
A structure which contains a char pointer which points to the first character of a file.
The name of the file.
The last character in the file.

Correct

The fp is a structure which contains a char pointer which points to the first character of a file.

Incorrect

The fp is a structure which contains a char pointer which points to the first character of a file.

Question 4 of 30

4. Question

Which of the following operations can be performed on the file “NOTES.TXT” using the below code?

FILE *fp;
fp = fopen("NOTES.TXT", "r+");

Reading
Writing
Appending
Read and Write

Correct

r+ Open an existing file for update (reading and writing).

Incorrect

r+ Open an existing file for update (reading and writing).

Question 5 of 30

5. Question

To print out a and b given below, which of the following printf() statement will you use?

#include

float a=3.14;
double b=3.14;

printf("%f %lf", a, b);
printf("%Lf %f", a, b);
printf("%Lf %Lf", a, b);
printf("%f %Lf", a, b);

Correct

To print a float value, %f is used as format specifier.

To print a double value, %lf is used as format specifier.

Therefore, the answer is printf(“%f %lf”, a, b);

Incorrect

To print a float value, %f is used as format specifier.

To print a double value, %lf is used as format specifier.

Therefore, the answer is printf(“%f %lf”, a, b);

Question 6 of 30

6. Question

Which files will get closed through the fclose() in the following program?

#include

int main()
{
    FILE *fs, *ft, *fp;
    fp = fopen("A.C", "r");
    fs = fopen("B.C", "r");
    ft = fopen("C.C", "r");
    fclose(fp, fs, ft);
    return 0;
}

"A.C" "B.C" "C.C"
"B.C" "C.C"
"A.C"
Error in fclose()

Correct

Extra parameter in call to fclose().

Incorrect

Extra parameter in call to fclose().

Question 7 of 30

7. Question

On executing the below program what will be the contents of ‘target.txt’ file if the source file contains a line “To err is human”?

#include

int main()
{
    int i, fss;
    char ch, source[20] = "source.txt", target[20]="target.txt", t;
    FILE *fs, *ft;
    fs = fopen(source, "r");
    ft = fopen(target, "w");
    while(1)
    {
        ch=getc(fs);
        if(ch==EOF)
            break;
        else
        {
            fseek(fs, 4L, SEEK_CUR);
            fputc(ch, ft);
        }
    }
    return 0;
}

r n
Trh
err
None of above

Correct

The file source.txt is opened in read mode and target.txt is opened in write mode. The file source.txt contains “To err is human”.

Inside the while loop,

ch=getc(fs); The first character(‘T’) of the source.txt is stored in variable ch and it’s checked for EOF.

if(ch==EOF) If EOF(End of file) is true, the loop breaks and program execution stops.

If not EOF encountered, fseek(fs, 4L, SEEK_CUR); the file pointer advances 4 character from the current position. Hence the file pointer is in 5th character of file source.txt.

fputc(ch, ft); It writes the character ‘T’ stored in variable ch to target.txt.

The while loop runs three times and it write the character 1st and 5th and 11th characters (“Trh”) in the target.txt file.

Incorrect

The file source.txt is opened in read mode and target.txt is opened in write mode. The file source.txt contains “To err is human”.

Inside the while loop,

ch=getc(fs); The first character(‘T’) of the source.txt is stored in variable ch and it’s checked for EOF.

if(ch==EOF) If EOF(End of file) is true, the loop breaks and program execution stops.

If not EOF encountered, fseek(fs, 4L, SEEK_CUR); the file pointer advances 4 character from the current position. Hence the file pointer is in 5th character of file source.txt.

fputc(ch, ft); It writes the character ‘T’ stored in variable ch to target.txt.

The while loop runs three times and it write the character 1st and 5th and 11th characters (“Trh”) in the target.txt file.

Question 8 of 30

8. Question

To scan a and b given below, which of the following scanf() statement will you use?

#include

float a;
double b;

scanf("%f %f", &a, &b);
scanf("%Lf %Lf", &a, &b);
scanf("%f %Lf", &a, &b);
scanf("%f %lf", &a, &b);

Correct

To scan a float value, %f is used as format specifier.

To scan a double value, %lf is used as format specifier.

Therefore, the answer is scanf(“%f %lf”, &a, &b);

Incorrect

To scan a float value, %f is used as format specifier.

To scan a double value, %lf is used as format specifier.

Therefore, the answer is scanf(“%f %lf”, &a, &b);

Question 9 of 30

9. Question
Out of fgets() and gets() which function is safe to use?
- gets()
- fgets()
Correct

Because, In fgets() we can specify the size of the buffer into which the string supplied will be stored.

Incorrect

Because, In fgets() we can specify the size of the buffer into which the string supplied will be stored.

Question 10 of 30

10. Question

Consider the following program and what will be content of t?

#include

int main()
{
    FILE *fp;
    int t;
    fp = fopen("DUMMY.C", "w");
    t = fileno(fp);
    printf("%d\n", t);
    return 0;
}

size of "DUMMY.C" file
The handle associated with "DUMMY.C" file
Garbage value
Error in fileno()

Correct

fp = fopen(“DUMMY.C”, “w”); A file DUMMY.C is opened in write mode and returns the file pointer to fp

t = fileno(fp); returns the handle for the fp stream and it stored in the variable t

printf(“%d\n”, t); It prints the handle number.

Incorrect

fp = fopen(“DUMMY.C”, “w”); A file DUMMY.C is opened in write mode and returns the file pointer to fp

t = fileno(fp); returns the handle for the fp stream and it stored in the variable t

printf(“%d\n”, t); It prints the handle number.

Question 11 of 30

11. Question

What will be the content of ‘file.c’ after executing the following program?

#include

int main()
{
    FILE *fp1, *fp2;
    fp1=fopen("file.c", "w");
    fp2=fopen("file.c", "w");
    fputc('A', fp1);
    fputc('B', fp2);
    fclose(fp1);
    fclose(fp2);
    return 0;
}

B
A B
B B
Error in opening file 'file1.c'

Correct

Here fputc(‘A’, fp1); stores ‘A’ in the file1.c then fputc(‘B’, fp2); overwrites the contents of the file1.c with value ‘B’. Because the fp1 and fp2 opens the file1.c in write mode.

Hence the file1.c contents is ‘B’.

Incorrect

Hence the file1.c contents is ‘B’.

Question 12 of 30

12. Question

What will be the output of the program ?

#include

int main()
{
    int k=1;
    printf("%d == 1 is" "%s\n", k, k==1?"TRUE":"FALSE");
    return 0;
}

k == 1 is TRUE
1 == 1 is TRUE
1 == 1 is FALSE
K == 1 is FALSE

Correct

Step 1: int k=1; The variable k is declared as an integer type and initialized to ‘1’.

Step 2: printf(“%d == 1 is” “%s\n”, k, k==1?”TRUE”:”FALSE”); becomes

=> k==1?”TRUE”:”FALSE”

=> 1==1?”TRUE”:”FALSE”

=> “TRUE”

Therefore the output of the program is 1 == 1 is TRUE

Incorrect

Step 1: int k=1; The variable k is declared as an integer type and initialized to ‘1’.

Step 2: printf(“%d == 1 is” “%s\n”, k, k==1?”TRUE”:”FALSE”); becomes

=> k==1?”TRUE”:”FALSE”

=> 1==1?”TRUE”:”FALSE”

=> “TRUE”

Therefore the output of the program is 1 == 1 is TRUE

Question 13 of 30

13. Question

What will be the output of the program ?

#include
char *str = "char *str = %c%s%c; main(){ printf(str, 34, str, 34);}";

int main()
{
    printf(str, 34, str, 34);
    return 0;
}

char *str = "char *str = %c%s%c; main(){ printf(str, 34, str, 34);}"; main(){ printf(str, 34, str, 34);}
char *str = %c%s%c; main(){ printf(str, 34, str, 34);}
No output
Error in program

Correct

Incorrect

Question 14 of 30

14. Question

If the file ‘source.txt’ contains a line “Be my friend” which of the following will be the output of below program?

#include

int main()
{
    FILE *fs, *ft;
    char c[10];
    fs = fopen("source.txt", "r");
    c[0] = getc(fs);
    fseek(fs, 0, SEEK_END);
    fseek(fs, -3L, SEEK_CUR);
    fgets(c, 5, fs);
    puts(c);
    return 0;
}

friend
frien
end
Error in fseek();

Correct

The file source.txt contains “Be my friend”.

fseek(fs, 0, SEEK_END); moves the file pointer to the end of the file.

fseek(fs, -3L, SEEK_CUR); moves the file pointer backward by 3 characters.

fgets(c, 5, fs); read the file from the current position of the file pointer.

Hence, it contains the last 3 characters of “Be my friend”.

Therefore, it prints “end”.

Incorrect

The file source.txt contains “Be my friend”.

fseek(fs, 0, SEEK_END); moves the file pointer to the end of the file.

fseek(fs, -3L, SEEK_CUR); moves the file pointer backward by 3 characters.

fgets(c, 5, fs); read the file from the current position of the file pointer.

Hence, it contains the last 3 characters of “Be my friend”.

Therefore, it prints “end”.

Question 15 of 30

15. Question

What will be the output of the program ?

#include

int main()
{
    float a=3.15529;
    printf("%2.1f\n", a);
    return 0;
}

3.00
3.15
3.2
3

Correct

float a=3.15529; The variable a is declared as an float data type and initialized to value 3.15529;

printf(“%2.1f\n”, a); The precision specifier tells .1f tells the printf function to place only one number after the .(dot).

Hence the output is 3.2

Incorrect

float a=3.15529; The variable a is declared as an float data type and initialized to value 3.15529;

printf(“%2.1f\n”, a); The precision specifier tells .1f tells the printf function to place only one number after the .(dot).

Hence the output is 3.2

Question 16 of 30

16. Question

What will be the output of the program ?

#include

int main()
{
    printf("%c\n", ~('C'*-1));
    return 0;
}

Correct

Incorrect

Question 17 of 30

17. Question

What will be the output of the program ?

#include

int main()
{
    FILE *fp;
    unsigned char ch;
     /* file 'abc.c' contains "This is IndiaBIX " */
    fp=fopen("abc.c", "r");
    if(fp == NULL)
    {
        printf("Unable to open file");
        exit(1);
    }
    while((ch=getc(fp)) != EOF)
        printf("%c", ch);

    fclose(fp);
    printf("\n", ch);
    return 0;
}

This is IndiaBIX
This is
Infinite loop
Error

Correct

The macro EOF means -1.

while((ch=getc(fp)) != EOF) Here getc function read the character and convert it to an integer value and store it in the variable ch, but it is declared as an unsigned char. So the while loop runs infinitely.

Incorrect

The macro EOF means -1.

Question 18 of 30

18. Question

What will be the output of the program ?

#include

int main()
{
    char *p;
    p="%d\n";
    p++;
    p++;
    printf(p-2, 23);
    return 0;
}

21
23
Error
No output

Correct

Incorrect

Question 19 of 30

19. Question

What will be the output of the program ?

#include

int main()
{
    FILE *ptr;
    char i;
    ptr = fopen("myfile.c", "r");
    while((i=fgetc(ptr))!=NULL)
        printf("%c", i);
    return 0;
}

Print the contents of file "myfile.c"
Print the contents of file "myfile.c" upto NULL character
Infinite loop
Error in program

Correct

The program will generate infinite loop. When an EOF is encountered fgetc() returns EOF. Instead of checking the condition for EOF we have checked it for NULL. so the program will generate infinite loop.

Incorrect

Question 20 of 30

20. Question

What will be the output of the program ?

#include

int main()
{
    printf("%%%%\n");
    return 0;
}

%%%%%
%%
No output
Error

Correct

Incorrect

Question 21 of 30

21. Question

What will be the output of the program ?

#include

int main()
{
    int a=250;
    printf("%1d\n", a);
    return 0;
}

1250
2
50
250

Correct

int a=250; The variable a is declared as an integer type and initialized to value 250.

printf(“%1d\n”, a); It prints the value of variable a.

Hence the output of the program is 250.

Incorrect

int a=250; The variable a is declared as an integer type and initialized to value 250.

printf(“%1d\n”, a); It prints the value of variable a.

Hence the output of the program is 250.

Question 22 of 30

22. Question

What will be the output of the program ?

#include

int main()
{
    FILE *fp;
    char ch, str[7];
    fp=fopen("try.c", "r"); /* file 'try.c' contains "This is Nagpur" */
    fseek(fp, 9L, SEEK_CUR);
    fgets(str, 5, fp);
    puts(str);
    return 0;
}

agpur
gpur
Nagp
agpu

Correct

Incorrect

Question 23 of 30

23. Question

What will be the output of the program if value 25 given to scanf()?

#include

int main()
{
    int i;
    printf("%d\n", scanf("%d", &i));
    return 0;
}

Correct

The scanf function returns the number of input is given.

printf(“%d\n”, scanf(“%d”, &i)); The scanf function returns the value 1(one).

Therefore, the output of the program is ‘1’.

Incorrect

The scanf function returns the number of input is given.

printf(“%d\n”, scanf(“%d”, &i)); The scanf function returns the value 1(one).

Therefore, the output of the program is ‘1’.

Question 24 of 30

24. Question

Point out the error in the program?

#include
#include

int main()
{
    unsigned char;
    FILE *fp;
    fp=fopen("trial", "r");
    if(!fp)
    {
        printf("Unable to open file");
        exit(1);
    }
    fclose(fp);
    return 0;
}

Error: in unsigned char statement
Error: unknown file pointer
No error
None of above

Correct

This program tries to open the file trial.txt in read mode. If file not exists or unable to read it prints “Unable to open file” and then terminate the program.

If file exists, it simply close the file and then terminates the program.

Incorrect

This program tries to open the file trial.txt in read mode. If file not exists or unable to read it prints “Unable to open file” and then terminate the program.

If file exists, it simply close the file and then terminates the program.

Question 25 of 30

25. Question

Point out the error in the program?

#include

int main()
{
    char ch;
    int i;
    scanf("%c", &i);
    scanf("%d", &ch);
    printf("%c %d", ch, i);
    return 0;
}

Error: suspicious char to in conversion in scanf()
Error: we may not get input for second scanf() statement
No error
None of above

Correct

Incorrect

Question 26 of 30

26. Question

Point out the error in the program?

#include

int main()
{
    FILE *fp;
    fp=fopen("trial", "r");
    fseek(fp, "20", SEEK_SET);
    fclose(fp);
    return 0;
}

Error: unrecognised Keyword SEEK_SET
Error: fseek() long offset value
No error
None of above

Correct

Instead of “20” use 20L since fseek() need a long offset value.

Incorrect

Instead of “20” use 20L since fseek() need a long offset value.

Question 27 of 30

27. Question

Point out the error in the program?

#include

/* Assume there is a file called 'file.c' in c:\tc directory. */
int main()
{
    FILE *fp;
    fp=fopen("c:\tc\file.c", "r");    
    if(!fp) 
      printf("Unable to open file.");        

    fclose(fp);
    return 0;
}

No error, No output.
Program crashes at run time.
Output: Unable to open file.
None of above

Correct

The path of file name must be given as “c:\\tc\file.c”

Incorrect

The path of file name must be given as “c:\\tc\file.c”

Question 28 of 30

28. Question

Point out the error/warning in the program?

#include

int main()
{
    unsigned char ch;
    FILE *fp;
    fp=fopen("trial", "r");
    while((ch = getc(fp))!=EOF)
        printf("%c", ch);
    fclose(fp);
    return 0;
}

Error: in unsigned char declaration
Error: while statement
No error
It prints all characters in file "trial"

Correct

Here, EOF is -1. As ‘ch’ is declared as unsigned char it cannot deal with any negative value.

Incorrect

Here, EOF is -1. As ‘ch’ is declared as unsigned char it cannot deal with any negative value.

Question 29 of 30

29. Question

Which of the following statement is correct about the program?

#include

int main()
{
    FILE *fp;
    char ch;
    int i=1;
    fp = fopen("myfile.c", "r");
    while((ch=getc(fp))!=EOF)
    {
        if(ch == '\n')
            i++;
    }
    fclose(fp);
    return 0;
}

The code counts number of characters in the file
The code counts number of words in the file
The code counts number of blank lines in the file
The code counts number of lines in the file

Correct

This program counts the number of lines in the file myfile.c by counting the character ‘\n’ in that file.

Incorrect

This program counts the number of lines in the file myfile.c by counting the character ‘\n’ in that file.

Question 30 of 30

30. Question

Which of the following statement is correct about the program?

#include

int main()
{
    FILE *fp;
    char str[11], ch;
    int i=0;
    fp = fopen("INPUT.TXT", "r");
    while((ch=getc(fp))!=EOF)
    {
        if(ch == '\n' || ch == ' ')
        {
            str[i]='\0';
            strrev(str);
            printf("%s", str);
            i=0;
        }
        else
            str[i++]=ch;
    }
    fclose(fp);
    return 0;
}

The code writes a text to a file
The code reads a text files and display its content in reverse order
The code writes a text to a file in reverse order
None of above

Correct

This program reads the file INPUT.TXT and store it in the string str after reversing the string using strrev function.

Incorrect

This program reads the file INPUT.TXT and store it in the string str after reversing the string using strrev function.

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