Computer Knowledge - MCQ Practice Questions

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.

A pointer is a variable that stores the memory address of another variable. It is declared using the * symbol.

malloc() (memory allocation) allocates a block of memory dynamically during program execution and returns a pointer to it.

Arrays in C are declared with square brackets containing the size, followed by initialization in curly braces. Option A is the correct syntax.

In C, if a function's return type is not explicitly specified, it defaults to int. However, modern C standards require explicit return type declaration.

The break statement immediately terminates the loop and transfers control to the statement following the loop.

The arrow operator (->) is used to access structure members through a pointer. The dot operator (.) is used for direct access.

#define is a preprocessor directive used to define symbolic constants (macros) and performs text substitution before compilation.

To explicitly declare a function with no parameters in C, use 'void' as the parameter. int func(); is ambiguous in older C standards.

Due to memory alignment/padding: int x (4 bytes), char c (1 byte) + 3 bytes padding, int y (4 bytes) = 12 bytes total. The compiler adds padding to align data members to their natural boundaries for efficient memory access.

Both {} and {0} will initialize all array elements to 0. When you provide fewer initializers than array size, remaining elements are automatically set to 0.

A pointer to a pointer is declared using two asterisks (). int ptr declares a pointer that points to another pointer that points to an integer.

Variables declared inside a function have local scope (also called function scope). They are only accessible within that function and are destroyed when the function returns.