Question 1

To scan a and b given below, which of the following scanf() statement will you use? #include<stdio.h>

float a;
double b;

Accepted Answer

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 2

Out of fgets() and gets() which function is safe to use?

Accepted Answer

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

Question 3

To print out a and b given below, which of the following printf() statement will you use? #include<stdio.h>

float a=3.14;
double b=3.14;

Accepted Answer

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 4

In a file contains the line "I am a boy
" then on reading this line into the array str using fgets(). What will str contain?

Accepted Answer

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
\0"

Question 5

Which files will get closed through the fclose() in the following program? #include<stdio.h>

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…

Accepted Answer

Extra parameter in call to fclose().

Question 6

What is the purpose of "rb" in fopen() function used below in the code? FILE *fp;
fp = fopen("source.txt", "rb");

Accepted Answer

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

Question 7

Consider the following program and what will be content of t? #include<stdio.h>

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

Accepted Answer

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
", t); It prints the handle number.

Question 8

What does fp point to in the program? #include<stdio.h>

int main()
{
    FILE *fp;
    fp=fopen("trial", "r");
    return 0;
}

Accepted Answer

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

Question 9

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<stdio.h>

int main()
{
    int i, fss;
    char ch, source[20] = "source.txt", target[20]="target.txt", t;
 …

Accepted Answer

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 10

Which of the following operations can be performed on the file "NOTES.TXT" using the below code? FILE *fp;
fp = fopen("NOTES.TXT", "r+");

Accepted Answer

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

Question 11

What will be the content of 'file.c' after executing the following program? #include<stdio.h>

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

Accepted Answer

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'.

Question 12

What will be the output of the program? #include<stdio.h>

int main()
{
    int k=1;
    printf("%d == 1 is" "%s
", k, k==1?"TRUE":"FALSE");
    return 0;
}

Accepted Answer

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
", 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

What will be the output of the program? #include<stdio.h>

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

Accepted Answer

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.

Question 14

What will be the output of the program? #include<stdio.h>

int main()
{
    float a=3.15529;
    printf("%2.1f
", a);
    return 0;
}

Accepted Answer

float a=3.15529; The variable a is declared as an float data type and initialized to value 3.15529; printf("%2.1f
", 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 15

What will be the output of the program? #include<stdio.h>

int main()
{
    int a=250;
    printf("%1d
", a);
    return 0;
}

Accepted Answer

int a=250; The variable a is declared as an integer type and initialized to value 250. printf("%1d
", a); It prints the value of variable a. Hence the output of the program is 250.

Question 16

What will be the output of the program if value 25 given to scanf()? #include<stdio.h>

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

Accepted Answer

The scanf function returns the number of input is given. printf("%d
", scanf("%d", &i)); The scanf function returns the value 1(one). Therefore, the output of the program is '1'.

Question 17

What will be the output of the program? #include<stdio.h>

int main()
{
    FILE *fp;
    unsigned char ch;
     /* file 'abc.c' contains "This is CuriousTab " */
    fp=fopen("abc.c", "r");
    if(fp == NULL)
    {
        printf("Unable …

Accepted Answer

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.

Input / Output Questions