UNIT III - LOADERS AND LINKERS

1. Write the two passes of a linking loader. 

Pass1: assigns address to all external symbols 

Pass2: it performs actual loading, relocation and linking. 

2. Define automatic library search.

 In many linking loaders the subroutines called by the program being loaded are automatically fetched from the library, linked with the main program and loaded. This feature is referred to as automatic library search.

3. List the loader options INCLUDE &DELETE. 

The general format of INCLUDE is INCLUDE program_name (library name) 

This command directs the loader to read the designated object program from a library and treat it as the primary loader input.

 The general format of DELETE command is DELETE Csect-name 

It instructs the loader to delete the named control sections from the sets of programs loaded. 

4. Give the functions of the linking loader.

 The linking loader performs the process of linking and relocation. It includes the operation of automatic library search and the linked programs are directly loaded into the memory.

 5. Define dynamic linking. 

If the subroutine is loaded and linked to the program during its first call (run time), then it is called as dynamic loading or dynamic linking. 

6. Write the advantage of dynamic linking.

 It has the ability to load the routine only when they are needed.

 The dynamic linking avoids the loading of entire library for each execution.

7. What is meant by static executable and dynamic executable? 

In static executable, all external symbols are bound and ready to run. In dynamic executables some symbols are bound at run time.

 8. What is shared and private data? The data divided among processing element is called shared data. If the data is not shared among processing elements then it is called private data.

9. Write the absolute loader algorithm

 Begin

 Read Header record 

Verify program name and length

 Read first text record 

While record type != „E‟ 

do

Begin 

Move object code to specified location in memory 

Read next object program record 

End 

Jump to address specified in End record

 End