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.