*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.

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.

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.

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.

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

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.

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.

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

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

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