Computer Knowledge - MCQ Practice Questions

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().

Variable names in C must start with a letter or underscore, not a digit. _variable is valid. '2var' starts with digit, 'var-name' contains hyphen (invalid), 'var name' contains space (invalid).

The strlen() function returns the length of a string as an int value, representing the number of characters.

Parentheses () have the highest precedence among all operators in C. They are always evaluated first in any expression.

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.