Computer Knowledge - MCQ Practice Questions

malloc() returns a void pointer (void*) which can be cast to any pointer type. It returns NULL if memory allocation fails.

The free() function deallocates memory that was previously allocated using malloc(), calloc(), or realloc(). delete() is used in C++.

calloc(n, size) allocates n blocks of size bytes and initializes to 0. malloc(size) allocates size bytes without initialization. calloc() is typically slower due to initialization.

/* */ is used for multi-line comments in C. // is used for single-line comments and was introduced in C99.

Since both 5 and 2 are integers, integer division occurs ($\frac{5}{2}$ = 2). The result 2 is then converted to float as 2.000000.

In structures, each member has its own memory location. In unions, all members share the same memory location, so only one can hold a value at a time.

++a increments a to 6 and returns 6. Then a++ returns 6 and increments a to 7. So b = 6 + 6 = 12.

The left shift operator (<<) shifts bits to the left by 1 position, which is equivalent to multiplying by 2. So 5 << 1 = 10.

p points to arr, so p[5] is equivalent to *(p+5) which gives the value at arr[5].

The void pointer is a generic pointer that can hold addresses of any data type. void is also used for functions returning nothing and parameters.

All three functions can read strings, though gets() is deprecated due to security issues. fgets() is safer as it limits input size.

sizeof(arr) gives total size of array. sizeof(arr[0]) gives size of one element. Dividing gives the number of elements: $\frac{20}{4}$ = 5.

The %d format specifier prints the ASCII value of the character. 'A' has ASCII value 65.

sizeof(arr) returns the total size of the array in bytes. An array of 5 integers, where each int is 4 bytes, equals 5 × 4 = 20 bytes.

malloc() is the standard C library function for dynamic memory allocation. It returns a void pointer to the allocated memory block, which can be cast to the required data type.

The break statement terminates the current loop or switch block and transfers control to the statement following the loop or switch. Without it, execution continues to the next case (fall-through).

The condition x < y evaluates to true (5 < 10), so the if block executes, printing 'yes'. The else block is skipped.

C supports pass by value and pass by pointer/address. 'Pass by reference' as a concept exists in C++, not in C. In C, to achieve reference-like behavior, we use pointers.

The modulus operator % returns the remainder of division. 10 % 3 = 1 (since 10 = 3 × 3 + 1). Therefore, c = 1 and the output is 1.

When a character is printed using %d format specifier, its ASCII value is printed. The ASCII value of 'A' is 65.