Programming Fundamentals

Abstraction focuses on exposing only essential features while hiding implementation details. It's about showing what an object does rather than how it does it. Encapsulation is about bundling data and methods together, while information hiding is a related concept about restricting access to internal details.

Inline functions are expanded at compile time - the compiler replaces the function call with the actual function code, eliminating the overhead of function call mechanism. Virtual functions use dynamic binding, static functions have class scope, and friend functions are non-member functions with special access rights.

A Null pointer is a pointer of any data type that does not point to any valid memory location and generally holds a value of zero. Vptr is a virtual table pointer, Void represents a pointer to an unspecified data type, and Zero is not a standard pointer type.

Storage classes in C are auto (default for local variables, stored on stack), static (retains value between calls, stored in data segment), extern (variables defined in another file), and register (stored in CPU registers). 'Global' is not a storage class - global variables use extern or static storage classes.

Friend functions are granted special access to private and protected members of a class. They're not member functions themselves but can access non-public data. This provides controlled way to expose private data to specific external functions without making it public.

In C++, if no return type is specified for a function, the default return type is 'int'. This is a legacy feature from C. However, it's considered poor practice - always explicitly specify the return type. The 'void' return type means the function returns nothing, while 'bool' is for boolean return values.

In C#, boxing converts value types to reference types, and unboxing reverses this. During boxing, the runtime creates a temporary reference type object on the heap to hold the value type. Reference types are stored on the heap, not the stack (option A is wrong), and identifiers can contain numeric characters (option D is wrong).

C# allows multiple Main() methods in different classes, but you must specify which one is the entry point using compiler options. The compiler returns an error if multiple Main() methods exist without an explicit entry point specification. Option A is wrong because you CAN define multiple Main() methods.

C# identifiers are names for variables, classes, structs, etc. They must begin with a letter or underscore, are case-sensitive (option B is wrong), and can contain numeric characters after the first character (option D is wrong).

COBOL's PERFORM...UNTIL executes the loop body first, then checks the condition - similar to do-while in Java/C++ (condition checked at bottom, guaranteed at least one iteration). PERFORM...VARYING is more like a for loop.

The PERFORM statement with the AFTER clause in COBOL creates a loop that executes the body first, then checks the condition for subsequent iterations. This is equivalent to a do-while loop in other languages.

When an IF condition evaluates to true, the statements within the THEN branch (the code block associated with the true condition) are executed as part of normal program flow.

NEXT SENTENCE transfers control to the statement immediately after the next period (sentence terminator), while CONTINUE transfers control to the statement after the explicit scope terminator (like END-IF or END-PERFORM). They are not equivalent.

WS-N starts at 0, gets set to 5, then PERFORM B-PARA WS-N TIMES executes B-PARA exactly 5 times. The fact that B-PARA changes WS-N to 10 doesn't affect the loop count - PERFORM TIMES evaluates the count once at the start.