【正文】 Loaders ? In object code the primary memory references are made relative to an undetermined starting location that can be anywhere in memory. ? Loader will resolve all relocateable addresses to a given starting address. ? Usually, the loading process is part of OS. Preprocessors ? A preprocessor is a separate program that is called by the piler before the translation begins. ? Preprocessors can – Delete ments – Include other files – Perform macro substitutions ? A macro is a shorthand description of a repeated sequence of text Editors ? Source programs are written using an editor that produces a standard file (ASCII). ? Recently, pilers have been bundled with editors and other programs into an interactive development environment (IDE). ? Such editors may be oriented towards the format of programming language. – Programmer may be informed of errors as the program is written. ? The piler can be called from within the editor. Debuggers ? A debugger is a program that determines execution errors in a piled program. – It is also packaged in IDE. ? The debugger keeps track of the source code information such as line numbers, names of variables and procedures. ? It can halt execution at breakpoint and provide information on called functions and current values of variables. Its Role in the Computer System Hardware OS Compiler High Level Language Other Facilities Translation Process Scanner Parser Semantic Analyzer Source Code Optimizer Code Generator Target Code Optimizer Source Code Target Code Tokens Syntax Tree Intermediate code Target Code Literal Table Symbol Table Error Handler Why to Study it ? ? 1 Obtain the Knowledge about Compiler ? 2 Write good quality program code ? 3 Obtain the Knowledge about system software construction to improve programming skills ? 4 Learn how to apply the theories into software construction ( Data Structure ,Discrete Math , Formal Language and Automata, etc ) ? 5 Lay a solid base for future research work on the puter science ( Dose it really dead ? ) Its Application Cases ? 1 Embedded SQL ? 2 Extensions to Existed Languages ? 3 Develop a Dedicated Usage Languages ? ( Display Card Driver Generation Language, ? Game development Language , AI Language) ? 4 Construct CASE tools ( Oriented to SE research ) ? ( check software bug …) ? 5 To reduce the gaps between the software and hardware ( Oriented to CS research ) The Scanner ? Reads the source program (stream of characters). ? Performs lexical analysis: collects sequences of characters into meaningful units called tokens. ? Example: a[index] = 4 + 2。a[R0], 6 。 double value in R0 MOV R1, amp。 address of a R1 ADD R1, R0 。 value of index R0 SHL R0 。 a identifier [ left bracket index identifier ] right bracket = assignment 4 number + plus sign