Technical Questions

There is no difference except for the fact that the first one gives a hint that the function fun() is probably in another source file.

Logical address space is generated from CPU; it bound to a separate physical address space is central to proper memory management. Physical address space is seen by the memory unit. Logical address space is virtual address space. Both these address space will be same at compile time but differ at execution time.

Fragmentation occurs in a dynamic memory allocation system when many of the free blocks are too small to satisfy any request.

You can divide the frequency of a clock by just implementing T Flip flop.

Give clock as clock input and tie the T input to logic 1.

0  0  1

That's what some of the compilers would give. But some other compiler may give a different answer. The reason is, when a single expression causes the same object to be modified and then inspected the behaviour is undefined.

interrupt is a signal send by external device to the processor so as to request the processor to perform a particular work.

A signal informing a program that an events has occurred. when a program receives an interrupt signal, it takes a specified action (which can be to ignore the signal).

Execution Unit receives program instruction codes and data from BIU, executes these instructions and store the result in general registers.

Here we are initalising the function pointer p to the address of the function fun(). But during this initialisation the function has not been defined. Hence an error.

To eliminate this error add the prototype of the fun() before declaration of p, as shown below:

extern int fun();    or simply  int fun();