Inputs And Outputs : MCQs & PYQs with Explanation

Option A

In C programming, when we want to calculate the square root of a number, we use a predefined function called sqrt(). This function is available in the math.h header file, so we must include it at the beginning of the program using #include<math.h>.
#include <stdio.h>
#include <math.h>
int main()
{
    float num, result;
    printf("Enter a Number: ");
    scanf("%f", &num);
    result = sqrt(num);
    printf("Square Root of %f is %f",num,result);
    return 0;
}

Option C

In C language, different format specifiers are used to print numbers in various number systems. 
The octal representation of a number is printed using the %o format specifier. For hexadecimal output, C provides two specifiers, %x for lowercase letters (a–f) and %X for uppercase letters (A–F). For decimal output %d or %i is used.

• In C, for binary number system there is no any direct format specifier.

Option D

The scanf() is a formatted input function used to take input from the user. Besides reading input, scanf() also returns a value.
The return value of scanf() is the number of input values that are successfully read and assigned to the given variables.

Option C

Both printf() and scanf() are formatted input-output functions in C. The printf() function is used to display output on the screen using format specifiers while scanf() is used to read input from the user in a formatted manner using the format specifiers.

Option B

In C, the execution of program begins from main() function. Therefore, a C program can have only one main() function. Defining more than one main() function will cause a compilation error because the compiler will not know where to start executing the program.

Option B

The character 'a' is stored in the variable a. When we print it using %d, C prints its ASCII value. The ASCII value of 'a' is 97.

Option B

The printf() is not only used to display output, it also returns a value. The return value of printf() is the total number of characters printed on the screen.
The statement printf("%d %d", a, b); prints the value of a, then a newline, and then the value of b.

• Printing 10 : 2 characters.
• Printing : 1 character.
• Printing 20 : 2 characters.

So, the total number of characters printed is 5.
This value 5 is returned by printf() and stored in the variable r. Then printf("%d", r); prints the value of r, which is 5.

Option A

In C, both fgets() and gets() functions are used for input operations, specifically for reading strings from input. These functions are declared in the stdio.h (Standard Input-Output) header file.

Option B

Unformatted I/O functions do not use format specifiers and mainly work with single characters or strings. Example included getchar(), putchar(), gets(), puts(). These functions are simple and are mostly used for character-based input and output.

Although gets() is unsafe because it does not check the size of input, which may cause buffer overflow and removed in modern C. The fgets() is used instead of gets() because it is safe and size-bounded.
Syntax:
fgets(string_name,size,stdin);
E.g.: 
char name[50];
printf("Enter Name: ");
fgets(name,sizeof(name),stdin);

Option C

In C language, unformatted input/output functions are those functions that do not use format specifiers like %c, %d, %f, etc. and are mainly used for simple input or output, especially characters or strings. Commonly used unformatted I/O functions are getchar(), putchar(), gets(), puts().

• The clrscr() function is used to clear the screen.
• The sqrt() is a mathematical function used to calculate the square root of a number.
• The sleep() function is used to pause program execution for some time.