Loaders and Linkers T 李俊葦

1. Loader Accepts the object programs ， prepares these programs for execution by the computer ， and indicates the execution of four functions a. Allocation ： Allocate space in memory for the program b. Linking ： Resolve symbolic reference between object programs 。 c. Relocation ： Adjust all address - dependent locations ， such as address constant ， to corresponds to the allocated space 。 d. Loading ： Physically place the machine instructions and data into memory 。

Introduction

2. Linkage Editor

3. Linking Loader

3.2 Absolute Loader 1. Absolute loader Places machine code and data into memory at the location prescribed by the assembler 。 Allocation: programmer 。 Linking: programmer 。 Relocation: assembler 。 Loading: loader 。 * programmer must specifies the actual address * many functions may overlay each other

2. Bootstrap Loader When a computer is first turned on or restarted, a special type of absolute loader called a bootstrap loader is executed. The bootstrap loader will load operating system kernel to main memory. The bootstrap loader occupies a predefined memory, resident in a ROM.

Absolute Loader