C Programming MCQs with answers Page - 3

Explanation:

The correct answer is:

✅ (A) float

Explanation:

• In a union, all members share the same memory space, and its size is determined by the largest data type inside it.
• In this case, the union contains:
  • char ch; → 1 byte
  • int n; → typically 4 bytes
  • float f; → typically 4 bytes

How is Union Size Determined?

• A union only allocates one memory block large enough to store the largest member.
• Here, both int and float require 4 bytes each (assuming standard memory sizes).
• So, the union size is determined by float, which is the largest.
• If padding is involved (architecture-specific), it might be slightly larger to align the memory.

Example Code:

#include <stdio.h>



union temp {

    char ch;

    int n;

    float f;

};



int main() {

    printf("Size of union: %lu\n", sizeof(union temp));

    return 0;

}

Expected Output:

Size of union: 4

(If there's padding, it might be 8 bytes on some architectures.)

Final Answer:

✅ (A) float

Explanation:

Loss of precision happens when a type conversion leads to loss of fractional or significant digits. Let's analyze each option:

(A) float to int → ✅ Loss of precision

• Converting from float (which has a decimal part) to int (which only stores whole numbers) results in truncation (removal of the fractional part).
• Example:

(B) long to float → ⚠️ Possible loss of precision

• A long integer might have more significant digits than a float can accurately store.
• Example:
• But for smaller numbers, no loss occurs.

(C) float to double → ❌ No loss of precision

• double has more precision than float, so no data loss occurs.
• Example:

(D) char to short → ❌ No loss of precision

• char (1 byte) can easily fit into a short (2 bytes), so no precision loss occurs.

Final Answer:

✅ (A) float to int (because fractional values are lost).

float f = 3.14159f;

double d = (double) f;

printf("%lf", d); // No precision loss

long l = 9876543210;

float f = (float) l;

printf("%f", f); // May lose precision for very large values

float f = 5.99;

int i = (int) f;

printf("%d", i); // Output: 5 (fractional part is lost)

Explanation:

In a 32-bit compiler, the size of a float data type is 4 bytes (32 bits) because:

• A float in C follows the IEEE 754 single-precision floating-point standard, which uses:
  • 1 bit for the sign
  • 8 bits for the exponent
  • 23 bits for the mantissa (fraction)

Verification with C Code:

You can check the size of float using:

#include <stdio.h>

int main() {

    printf("Size of float: %zu bytes\n", sizeof(float));

    return 0;

}

Output:

Size of float: 4 bytes

Final Answer:

✅ (B) 4

Explanation:

In a 32-bit compiler, the typical sizes of fundamental data types are:

• int and float both take 4 bytes in a 32-bit compiler.
• double is 8 bytes, so option (A) is incorrect.
• short is 2 bytes while int is 4 bytes, so (B) is incorrect.
• char is 1 byte, while short is 2 bytes, so (C) is incorrect.

Final Answer:

✅ (D) int and float