C Programming - MCQ Practice Questions

extern is a declaration (not definition) that tells compiler the variable exists elsewhere in program. It provides global scope.

Due to structure padding/alignment, the size becomes 24 bytes (8-byte alignment for double). Members are padded to maintain alignment.

restrict prevents pointer aliasing (not allows). It tells compiler that pointer is the only way to access that object.

In C, floating-point constants like 3.14 are treated as double by default. To specify float, you need to use 3.14f suffix.

The C standard guarantees int is at least 2 bytes, but most 32-bit systems use 4 bytes. The exact size is implementation-dependent.

The declaration uses comma separation. 'int arr[10]' declares an array of 10 integers, while '*ptr' declares a pointer to int.

Both 'const int' and 'int const' are valid and equivalent ways to declare a constant integer in C.

unsigned char is 1 byte (8 bits) without sign bit, giving range 0 to 2^8-1 = 0 to 255.

C allows implicit type conversion. When assigning larger to smaller type, truncation or data loss may occur without any compiler error.

volatile tells the compiler that the variable's value may change unexpectedly (e.g., by hardware, signals, or another thread), so the compiler should not optimize it.

Variables declared inside a block (including function blocks) have block scope and are accessible only within that block.

The storage classes in C are: auto, register, static, and extern. 'static' is one of them.

# Understanding `sizeof()` Operator in C

The `sizeof()` operator returns the size of data types in bytes, which varies depending on the compiler and system architecture.

Step 1: Analyze sizeof(int)

In C, the size of `int` is implementation-defined and depends on the system architecture and compiler.

Step 2: Analyze sizeof(char) and Calculate Total

The `char` data type always occupies exactly 1 byte across all standard C implementations, but `int` varies by platform.

For a 16-bit system: $2+1=3$ bytes

For a 32-bit system: $4+1=5$ bytes

For a 64-bit system: $4+1=5$ bytes (typically)

The output depends on the system's architecture. The minimum guaranteed value is 3 bytes (on 16-bit systems), but it can be higher on modern systems.

Correct Answer: (C) Depends on system (at least 3)

char (signed) has range -128 to 127, while unsigned char has 0 to 255. The latter can represent extended ASCII characters (128-255).

When assigning a double to int, C performs implicit type conversion with truncation (not rounding). The decimal part is discarded.

Initialization assigns a value when the variable is declared (int x = 5;). Assignment changes the value later (x = 10;).

Uninitialized local variables contain garbage values (random data from memory). Static/global variables are initialized to 0 by default.

%ld is for long int, %lld is for long long int, and %d is for regular int. Using wrong specifier can cause undefined behavior.

The '*' applies only to the immediately following variable. So 'int *p' declares p as pointer to int, and 'q' is just an int.

restrict (C99) informs the compiler that a pointer is the sole accessor to the object, enabling optimization. It doesn't prevent modification.