Chapter 17 Programming Tools The Architecture of Computer Hardware and Systems Software: An Information Technology Approach 3rd Edition, Irv Englander John Wiley and Sons  2003

Chapter 17 Programming Tools 17-2 Programming Tools Overview  Editors  Assemblers  Debuggers  Compilers  Linkers  Loaders  Interpreters Integrated Development Environments (IDEs) combine several of the above programming tools

Chapter 17 Programming Tools 17-3 The Program Translation Process  Terms, terms, and more terms! Source Object Executable Translator Linker Loader

Chapter 17 Programming Tools 17-4 Visual Basic IDE

Chapter 17 Programming Tools 17-5 Program Text Editors  Word processors format the appearance of the text  Text editors  Format the spacing between words for legibility  Ideal for structured languages  Text is the same font size  Examples  DOS – Edit  Windows – Notepad, Wordpad  Unix / Linux – ed, vi, emacs  IDEs  MS Visual C++, Symantec Visual Cafe

Chapter 17 Programming Tools 17-6 Programming Language Categories  Machine Language  Binary coded instructions  Assembly Language  Symbolic coded instructions  Procedural Languages  procedural statements or arithmetic notation  Four-generation Languages  Natural language and nonprocedural statements  Object-oriented Languages  Combination of objects and procedures

Chapter 17 Programming Tools 17-7 Assembly Language  When to use  When speed or size of program is critical  Hybrid approach  Hardware Drivers  Can use specialized instructions  Disadvantages  Inherently machine specific  Architectures may become obsolete  Lack of programming structure

Chapter 17 Programming Tools 17-8 Assemblers  Binary code = machine code  Hex code  Assembly Language  Mnemonic names  op codes  Labels  memory addresses  Comments  Symbol table  Operations table  Memory Relocation  Cross Assembler

Chapter 17 Programming Tools 17-9 What Does This Program Do?

Chapter 17 Programming Tools LMC Program in Java  Use instructions in a more understandable language static int max (int x[]) { for (i=1; i<=3; i++) x[i] = input.getint(); max_int = x[1]; for (i=2; i<=3; i++) if (x[I] > max_int) max_int = x[I]; System.output.println(max_int); }

Chapter 17 Programming Tools Procedural Languages  COBOL  Wordy but easier to maintain  FORTRAN  Scientists and engineers  BASIC  Pascal  Highly structured teaching language  C  high-level commands and low-level access to hardware

Chapter 17 Programming Tools Object-Oriented Languages  SmallTalk  C++  Java  Based on C++  Platform independent

Chapter 17 Programming Tools Compilers  Translates high-level language into low- level instructions  High-level language: Source code  Machine-level: Object code  Changes, including bug fixes, require recompiling

Chapter 17 Programming Tools Language Components  Lexicon  All legal words in the language  Meaning and type  Syntax  grammar rules  Semantics  meaning of command

Chapter 17 Programming Tools Computer Language Descriptions  Narrative  Syntax (Railroad) Diagrams  BNF  Backus-Naur Form  Context-Free Grammar

Chapter 17 Programming Tools Railroad Diagram Examples

Chapter 17 Programming Tools Typical BNF Rules for Java

Chapter 17 Programming Tools Parsed English Sentence

Chapter 17 Programming Tools The Compilation Process Checks for errors Generates CPU instructions or library calls Updates internal tables

Chapter 17 Programming Tools Process of Parsing  Lexical analysis  Also known as scanning  Divides the string of input characters into single elements, tokens, based on strict computer punctuation  Syntactic analysis  Checks for errors in grammar rules  Semantic parsing  Determines the meaning of the string

Chapter 17 Programming Tools Source Code Instructions  Data declarations:  Data type such as floating point, integer  Data operations  Instructions that update or compute data value (lots of moving around!)  Control Structures  Branches, Goto (yetch!), If-then-else, loops such as While-do and Repeat-until  Function, procedure, or subroutine calls  Receives control via a call instruction, receives and possibly modifies parameters, and returns control to the instruction after the call

Chapter 17 Programming Tools Recursive Descent Parsing

Chapter 17 Programming Tools Optimization  Compiler analyzes code in order to  Reduce amount of code  Eliminate repeated operations  Reorganize parts of of the program to execute faster and more efficiently  Use computer resources more effectively  Example  Move a calculation repeated within the body of a loop that does not use any value modified by the loop  Different compilers can produce different results!

Chapter 17 Programming Tools Object file or object module Object file C library Executable file Linker Linking

Chapter 17 Programming Tools Linkers  Searches program libraries to find library routines used by the program  Library: collection of pre-written functions and subroutines made available to perform commonly required activities  Determines the memory locations that code from each module will occupy and relocates instructions by adjusting absolute references  Resolves references among files

Chapter 17 Programming Tools Why Link?  Construct single executable program from multiple object code files compiled at different times  Program can be subdivided into components and parceled out to different developers  Example  Main program and multiple subroutines written and compiled by different programmers at different times

Chapter 17 Programming Tools Loader  Loads binary files that have been linked into main memory  Program is ready for execution

Chapter 17 Programming Tools Interpreters  Translates source code instructions into machine language and executes it one statement at a time  Disadvantages  Longer to execute, particularly bad for loops  Uses more memory  Advantage  Faster testing and code modification  Examples of interpreted languages  Java, BASIC, LISP

Chapter 17 Programming Tools Interpreter vs. Compiler Resources during executionInterpreterCompiler Contents in memory Interpreter/compilerYesNo Source codePartialNo Executable codeYes CPU cycles Translation operationsYesNo Library linkingYesNo Application programYes

Chapter 17 Programming Tools Debuggers  Assembly language debuggers  Source code debuggers  Step through programs  Check variable values