Computer Knowledge - MCQ Practice Questions

The post-increment operator (x++) returns the current value of x before incrementing. So printf prints 5, and then x becomes 6.

In C, pointers are declared using the asterisk (*) symbol before the variable name. The syntax is 'datatype *pointer_name;'

Each char occupies 1 byte in memory. An array of 10 chars will occupy 10 × 1 = 10 bytes.

void is used in two contexts: (1) as a function return type when a function doesn't return a value, and (2) to declare a generic pointer (void *) that can point to any data type.

The ternary operator (condition ? true_value : false_value) evaluates the condition (a > b). Since 10 is not greater than 20, it returns b which is 20.

strlen() returns the length of a string without counting the null terminator ('\0'). For example, strlen("hello") returns 5, not 6.

This code exhibits undefined behavior because x is modified twice between sequence points without an intervening sequence point. The result depends on the compiler's implementation.

scanf() reads formatted input based on format specifiers and stops at whitespace. gets() reads a string until a newline is encountered. Note: gets() is deprecated due to buffer overflow vulnerabilities.

Both A and B are correct. Option A uses explicit type casting which is optional in C (not in C++). Option B avoids casting. Using sizeof(int) is preferred over hardcoding 4, as int size may vary across systems.

*ptr dereferences the pointer to access the value at the address it points to, which is x = 5. So both *ptr and x print 5.

strcpy() does not perform bounds checking. If the source string is longer than the destination buffer, it will write beyond the buffer boundary, causing a buffer overflow. This is a security vulnerability. Using strncpy() is safer.

ptr points to arr[0]. ptr + 1 points to arr[1]. *(ptr + 1) dereferences to get the value at arr[1] which is 20. Pointer arithmetic adds sizeof(int) to the address for each increment.

A static variable declared inside a function has local scope (visible only within that function) but persists for the entire program lifetime. Its value is retained between function calls and is initialized only once.

Step 1: Evaluate condition x < y → 10 < 20 → true. Step 2: Execute true branch: x++ returns 10, then x becomes 11. Step 3: z = 10. Step 4: printf prints x=11, y=20, z=10.

This code contains undefined behavior because variable 'a' is modified multiple times (a++, ++a) without intervening sequence points in the same expression. The order of evaluation is unspecified, making the result compiler-dependent.

Both declarations are equivalent. 'const int * const ptr' and 'int const * const ptr' declare a constant pointer to a constant integer. The first const makes the integer constant, the second const makes the pointer constant.

A 2D array is stored in row-major order in memory: 1,2,3,4,5,6,7,8,9. When ptr is cast to int*, ptr+5 points to the 6th element (0-indexed), which is 6.

Step 1: sizeof(arr) = 5 × sizeof(int) = 20 bytes (assuming 4-byte int). Step 2: sizeof(arr[0]) = sizeof(int) = 4 bytes. Step 3: 20 ÷ 4 = 5. This calculates the number of elements in the array.

In a struct, each member has its own memory allocation, so the total size is the sum of all members. In a union, all members share the same memory location, so the size equals the largest member. Only one member can hold a value at a time in a union.

The stdio.h header file contains declarations for standard input/output functions like printf() and scanf().