Difference between compile and go loader and relocating loader?

1 ANSWERS

1. Ali Abdullah
   

   Hi There, One method of performing the loader functions is to have the assembler run in one part of memory and place the assembled machine instructions and data, as they are assembled, directly into their assigned memory locations (Figure). When the assembly is completed, the assembler causes a transfer to the starting instruction of the program. This is a simple solution, involving no extra procedures. It is used by the WATFOR FORTRAN compiler and several other language processors. Such a loading scheme is commonly called "compile-and-go" or "assemble and-go." It is relatively easy to implement. The assembler simply places the code into core, and the "loader" consists of one instruction that transfers to the starting instruction of the newly assembled program. However, there are several apparent disadvantages. First, a portion of memory is wasted because the core occupied by the assembler is unavailable to the object program. Second, it is necessary to retranslate (assemble) the user's program deck every time it is run. Third, it is very difficult to handle multiple segments, especially if the source programs are in different languages (e.g., one subroutine in assembly language and another subroutine FORTRAN or PL/I). This last disadvantage makes it very difficult to produce orderly modular programs. we can say that here loader is not a separate prog.also the four important functions of loader as 1)allocation 2)linking 3)relocation 4)loading is not done independently byloader.

   Report (0) (0)  |   2 years, 6 month(s) ago