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. 

UNIT III - LOADERS AND LINKERS

1. What are the basic functions of loaders?

 Loading – brings the object program into memory for execution

 Relocation – modifies the object program so that it can be loaded at an address different from the location originally specified

 Linking – combines two or more separate object programs and also supplies the information needed to reference them.

2. Define absolute loader. 

The loader, which is used only for loading, is known as absolute loader. e.g. Bootstrap loader

3. What is meant by bootstrap loader? 

This is a special type of absolute loader which loads the first program to be run by the computer. (usually an operating system) 

4. What are relative (relocative) loaders?

 Loaders that allow for program relocation are called relocating (relocative) loaders.

5. What is the use of modification record? 

Modification record is used for program relocation. Each modification record specifies the starting address and the length of the field whose value is to be altered and also describes the modification to be performed.