The architecture of computer hardware and systems software an information technology approach ch17

The Program Translation Process Terms, terms, and more terms!. Source Object Executable Translator Linker Loader...  Translates high-level language into level instructions low- High-l

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

Programming Tools Overview

Integrated Development Environments (IDEs)

combine several of the above programming tools

The Program Translation Process

 Terms,

terms, and

more terms!

Source Object

Executable

Translator Linker

Loader

Visual Basic IDE

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

 Inherently machine specific

 Architectures may become obsolete

 Lack of programming structure

 Binary code = machine code

 Hex code

 Assembly Language

 Mnemonic names  op codes

 Labels  memory addresses

What Does This Program Do?

00 IN 901 ;input three numbers and save

01 STO 99 399

02 IN 901

03 STO 98 398

04 IN 901

05 STO 97 397 ;subtract number in 98 from that in 97

06 SUB 98 298 ;number in 97 larger

07 BRP 10 811 ;number in 98 larger, restore 98

08 LDA 98 598

09 BR 11 611

10 LDA 97 597 ;restore 97

11 STO 96 396 ;store larger of (97, 98) in 96

12 SUB 99 299 ;subtract number in 99 from larger

 Translates high-level language into level instructions

low- High-level language: Source code

 Machine-level: Object code

 Changes, including bug fixes, require

recompiling

Language Components

 Lexicon

 All legal words in the language

 Meaning and type

 Syntax

 grammar rules

 Semantics

 meaning of command

Computer Language Descriptions

Railroad Diagram Examples

Typical BNF Rules for Java

Parsed English Sentence

The Compilation Process

Process of Parsing

 Lexical analysis

 Also known as scanning

 Divides the string of input characters into single elements, tokens, based on strict computer punctuation

Source Code Instructions

 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

Recursive Descent Parsing

 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

Object file or object

Linking

 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

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

 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

Interpreter vs Compiler

Resources during execution Interpreter Compiler

Contents in memory

Interpreter/compiler Yes No

Source code Partial No

Executable code Yes Yes

CPU cycles

Translation operations Yes No

Library linking Yes No

Application program Yes Yes

 Assembly language debuggers

 Source code debuggers

 Step through programs

 Check variable values