DOCSLIB.ORG

Programming Language Concepts Control Flow

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Programming Language Concepts Control Flow Programming Language Concepts Control Flow Janyl Jumadinova 13-15 October, 2020 Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 1 / 25 Operators Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 2 / 25 Conditional operator \?" boolean-expression ? expression1 : expression2 A Very Unusual Operator: ? Most operators are either binary (+; −; ∗; <; ==; &&; etc:) or unary (\plus sign" +, \minus sign" -, ++, !, etc.). However, C and Java also have a ternary operator (takes 3 arguments). Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 3 / 25 A Very Unusual Operator: ? Most operators are either binary (+; −; ∗; <; ==; &&; etc:) or unary (\plus sign" +, \minus sign" -, ++, !, etc.). However, C and Java also have a ternary operator (takes 3 arguments). Conditional operator \?" boolean-expression ? expression1 : expression2 Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 3 / 25 For example: 5 < 10 ? 70 : −3 is 70, while 5 > 10 ? 70 : −3 is −3 A Very Unusual Operator: ? Conditional operator \?" boolean-expression ? expression1 : expression2 The boolean-expression is evaluated. If it is true, the value is expression1, otherwise it is expression2. Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 4 / 25 while 5 > 10 ? 70 : −3 is −3 A Very Unusual Operator: ? Conditional operator \?" boolean-expression ? expression1 : expression2 The boolean-expression is evaluated. If it is true, the value is expression1, otherwise it is expression2. For example: 5 < 10 ? 70 : −3 is 70, Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 4 / 25 A Very Unusual Operator: ? Conditional operator \?" boolean-expression ? expression1 : expression2 The boolean-expression is evaluated. If it is true, the value is expression1, otherwise it is expression2. For example: 5 < 10 ? 70 : −3 is 70, while 5 > 10 ? 70 : −3 is −3 Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 4 / 25 String operators: \Hello" + \world" Referencing/dereferencing operators (C): &; ∗; ! Many Other Operators Bitwise Operators 10j7 = 15 (bitwise \or") 10&7 = 2 (bitwise \and") 10 << 3 = 80 (left shift) 10 >> 1 = 5 (right shift) Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 5 / 25 Referencing/dereferencing operators (C): &; ∗; ! Many Other Operators Bitwise Operators 10j7 = 15 (bitwise \or") 10&7 = 2 (bitwise \and") 10 << 3 = 80 (left shift) 10 >> 1 = 5 (right shift) String operators: \Hello" + \world" Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 5 / 25 Many Other Operators Bitwise Operators 10j7 = 15 (bitwise \or") 10&7 = 2 (bitwise \and") 10 << 3 = 80 (left shift) 10 >> 1 = 5 (right shift) String operators: \Hello" + \world" Referencing/dereferencing operators (C): &; ∗; ! Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 5 / 25 Operators in Other Languages Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 6 / 25 Operators in Other Languages COBOL Operators: Arithmetic Logical (AND, OR, NOT) Relational (IS [NOT] LIKE, IS LESS THAN ..) Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 7 / 25 Data Categories: Variables Literals: String/Alphanumeric Literals and Numeric Literals Figurative Constants SPACE or SPACES - Acts like one or more spaces ZERO or ZEROS or ZEROES - Acts like one or more zeros QUOTE or QUOTES - Used instead of a quotation mark HIGH-VALUE or HIGH-VALUES - Uses the maximum value possible LOW-VALUE or LOW-VALUES - Uses the minimum value possible ALL literal - Allows a ordinary literal to act as Figurative Constant COBOL Basics Every variable must be described in the DATA DIVISION. Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 8 / 25 COBOL Basics Every variable must be described in the DATA DIVISION. Data Categories: Variables Literals: String/Alphanumeric Literals and Numeric Literals Figurative Constants SPACE or SPACES - Acts like one or more spaces ZERO or ZEROS or ZEROES - Acts like one or more zeros QUOTE or QUOTES - Used instead of a quotation mark HIGH-VALUE or HIGH-VALUES - Uses the maximum value possible LOW-VALUE or LOW-VALUES - Uses the minimum value possible ALL literal - Allows a ordinary literal to act as Figurative Constant Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 8 / 25 COBOL Basics Data Types: Numeric Alphanumeric (text/string) Alphabetic Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 9 / 25 9 Indicates the occurrence of a digit. X Indicates the occurrence of any character from the character set. A Indicates the occurrence of any alphabetic character (A to Z plus blank). V Indicates the position of the decimal point in a numeric value. S Indicates the presence of a sign and can only appear at the beginning of PIC. Declaring Data-Items in COBOL A variable (elementary item) declaration consists of a line in the DATA DIVISION that contains the following: A level number A data-name or identifier. A Picture clause. Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 10 / 25 Declaring Data-Items in COBOL A variable (elementary item) declaration consists of a line in the DATA DIVISION that contains the following: A level number A data-name or identifier. A Picture clause. 9 Indicates the occurrence of a digit. X Indicates the occurrence of any character from the character set. A Indicates the occurrence of any alphabetic character (A to Z plus blank). V Indicates the position of the decimal point in a numeric value. S Indicates the presence of a sign and can only appear at the beginning of PIC. Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 10 / 25 Group items are declared using a level number and a data name only. Hierarchical relationship between the various subordinate items of the group is expressed using level numbers. The higher the level number, the lower the item is in the hierarchy. Declaring Data-Items in COBOL It maybe convenient to treat a collection of elementary items as a single group { (e.g., group YearofBirth, MonthofBirth, DayOfBirth under the group name - DateOfBirth). Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 11 / 25 Declaring Data-Items in COBOL It maybe convenient to treat a collection of elementary items as a single group { (e.g., group YearofBirth, MonthofBirth, DayOfBirth under the group name - DateOfBirth). Group items are declared using a level number and a data name only. Hierarchical relationship between the various subordinate items of the group is expressed using level numbers. The higher the level number, the lower the item is in the hierarchy. Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 11 / 25 Assignment Statements in COBOL 1 MOVE statement (MOVE 25 TO NUM1 NUM3.) 2 Computation written out as COMPUTE var = var operator var. or by using ADD, DIVIDE, MULTIPLY, SUBTRACT ... GIVING. Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 12 / 25 Conditional Branches Familiar to most novice programmers: \if" and \if-else" statements \switch" statements Basic idea: if (condition) then ... else ... It wasn't always quite this easy, though Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 13 / 25 Conditional branches{switch statements In C and Java: switch(i) { case 0: case 2: case 4: System.out.println(i+": even, <= 4"); break; case 1: System.out.println(i+" is one"); break; default: } Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 14 / 25 Conditional branches{switch statements Without break statements? i=0; switch(i) { case 0: case 2: case 4: System.out.println(i+": even, <= 4"); case 1: System.out.println(i+" is one"); default: System.out.println(i+": odd or > 4"); } Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 15 / 25 But in Java and C, order of evaluation is important: int i = 10, j = 0, k = 0; if (i > 10 && 5/j < 3) { k = 5; } Since i > 10 is false, there is no need to look at the second condition{we already know that the \&&" will be false. Short Circuit Evaluation According to the laws of logic, order doesn't matter in \and": \p AND q" is the same as \q AND p". Similarly, for OR. Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 16 / 25 int i = 10, j = 0, k = 0; if (i > 10 && 5/j < 3) { k = 5; } Since i > 10 is false, there is no need to look at the second condition{we already know that the \&&" will be false. Short Circuit Evaluation According to the laws of logic, order doesn't matter in \and": \p AND q" is the same as \q AND p". Similarly, for OR. But in Java and C, order of evaluation is important: Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 16 / 25 Short Circuit Evaluation According to the laws of logic, order doesn't matter in \and": \p AND q" is the same as \q AND p". Similarly, for OR. But in Java and C, order of evaluation is important: int i = 10, j = 0, k = 0; if (i > 10 && 5/j < 3) { k = 5; } Since i > 10 is false, there is no need to look at the second condition{we already know that the \&&" will be false. Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 16 / 25 int i = 10, j = 0, k = 0; if ( 5/j < 3 && i > 10 ) { k = 5; } If we start with 5=j < 3, we"ll get a \division by zero" error. Short Circuit Evaluation If we switch the ordering: Janyl Jumadinova Programming Language Concepts Control Flow 13-15 October, 2020 17 / 25 Short Circuit Evaluation If we switch the ordering: int i = 10, j = 0, k = 0; if ( 5/j < 3 && i > 10 ) { k = 5; } If we start with 5=j < 3, we"ll get a \division by zero" error.
Load more

Recommended publications
  • 7. Control Flow First?
    Copyright (C) R.A. van Engelen, FSU Department of Computer Science, 2000-2004 Ordering Program Execution: What is Done 7. Control Flow First? Overview Categories for specifying ordering in programming languages: Expressions 1. Sequencing: the execution of statements and evaluation of Evaluation order expressions is usually in the order in which they appear in a Assignments program text Structured and unstructured flow constructs 2. Selection (or alternation): a run-time condition determines the Goto's choice among two or more statements or expressions Sequencing 3. Iteration: a statement is repeated a number of times or until a Selection run-time condition is met Iteration and iterators 4. Procedural abstraction: subroutines encapsulate collections of Recursion statements and subroutine calls can be treated as single Nondeterminacy statements 5. Recursion: subroutines which call themselves directly or indirectly to solve a problem, where the problem is typically defined in terms of simpler versions of itself 6. Concurrency: two or more program fragments executed in parallel, either on separate processors or interleaved on a single processor Note: Study Chapter 6 of the textbook except Section 7. Nondeterminacy: the execution order among alternative 6.6.2. constructs is deliberately left unspecified, indicating that any alternative will lead to a correct result Expression Syntax Expression Evaluation Ordering: Precedence An expression consists of and Associativity An atomic object, e.g. number or variable The use of infix, prefix, and postfix notation leads to ambiguity An operator applied to a collection of operands (or as to what is an operand of what arguments) which are expressions Fortran example: a+b*c**d**e/f Common syntactic forms for operators: The choice among alternative evaluation orders depends on Function call notation, e.g.
    [Show full text]
  • A Survey of Hardware-Based Control Flow Integrity (CFI)
    A survey of Hardware-based Control Flow Integrity (CFI) RUAN DE CLERCQ∗ and INGRID VERBAUWHEDE, KU Leuven Control Flow Integrity (CFI) is a computer security technique that detects runtime attacks by monitoring a program’s branching behavior. This work presents a detailed analysis of the security policies enforced by 21 recent hardware-based CFI architectures. The goal is to evaluate the security, limitations, hardware cost, performance, and practicality of using these policies. We show that many architectures are not suitable for widespread adoption, since they have practical issues, such as relying on accurate control flow model (which is difficult to obtain) or they implement policies which provide only limited security. CCS Concepts: • Security and privacy → Hardware-based security protocols; Information flow control; • General and reference → Surveys and overviews; Additional Key Words and Phrases: control-flow integrity, control-flow hijacking, return oriented programming, shadow stack ACM Reference format: Ruan de Clercq and Ingrid Verbauwhede. YYYY. A survey of Hardware-based Control Flow Integrity (CFI). ACM Comput. Surv. V, N, Article A (January YYYY), 27 pages. https://doi.org/10.1145/nnnnnnn.nnnnnnn 1 INTRODUCTION Today, a lot of software is written in memory unsafe languages, such as C and C++, which introduces memory corruption bugs. This makes software vulnerable to attack, since attackers exploit these bugs to make the software misbehave. Modern Operating Systems (OSs) and microprocessors are equipped with security mechanisms to protect against some classes of attacks. However, these mechanisms cannot defend against all attack classes. In particular, Code Reuse Attacks (CRAs), which re-uses pre-existing software for malicious purposes, is an important threat that is difficult to protect against.
    [Show full text]
  • Control-Flow Analysis of Functional Programs
    Control-flow analysis of functional programs JAN MIDTGAARD Department of Computer Science, Aarhus University We present a survey of control-flow analysis of functional programs, which has been the subject of extensive investigation throughout the past 30 years. Analyses of the control flow of functional programs have been formulated in multiple settings and have led to many different approximations, starting with the seminal works of Jones, Shivers, and Sestoft. In this paper, we survey control-flow analysis of functional programs by structuring the multitude of formulations and approximations and comparing them. Categories and Subject Descriptors: D.3.2 [Programming Languages]: Language Classifica- tions—Applicative languages; F.3.1 [Logics and Meanings of Programs]: Specifying and Ver- ifying and Reasoning about Programs General Terms: Languages, Theory, Verification Additional Key Words and Phrases: Control-flow analysis, higher-order functions 1. INTRODUCTION Since the introduction of high-level languages and compilers, much work has been devoted to approximating, at compile time, which values the variables of a given program may denote at run time. The problem has been named data-flow analysis or just flow analysis. In a language without higher-order functions, the operator of a function call is apparent from the text of the program: it is a lexically visible identifier and therefore the called function is available at compile time. One can thus base an analysis for such a language on the textual structure of the program, since it determines the exact control flow of the program, e.g., as a flow chart. On the other hand, in a language with higher-order functions, the operator of a function call may not be apparent from the text of the program: it can be the result of a computation and therefore the called function may not be available until run time.
    [Show full text]
  • MINING the DIGITAL INFORMATION NETWORKS This Page Intentionally Left Blank
    MINING THE DIGITAL INFORMATION NETWORKS This page intentionally left blank Mining the Digital Information Networks Proceedings of the 17th International Conference on Electronic Publishing Edited by Nikklas Lavesson Bllekinge Institute of Technology, Sweden Peter Linde Bllekinge Institute of Technology, Sweden and Panayiota Polydoratou Alexander Technological Educational Institute of Thessaloniki, Greece Amsterdam • Berlin • Tokyo • Washington, DC © 2013 The authors and IOS Press. All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without prior written permission from the publisher. ISBN 978-1-61499-269-1 (print) ISBN 978-1-61499-270-7 (online) Library of Congress Control Number: 2013941588 Publisher IOS Press BV Nieuwe Hemweg 6B 1013 BG Amsterdam Netherlands fax: +31 20 687 0019 e-mail: [email protected] Distributor in the USA and Canada IOS Press, Inc. 4502 Rachael Manor Drive Fairfax, VA 22032 USA fax: +1 703 323 3668 e-mail: [email protected] LEGAL NOTICE The publisher is not responsible for the use which might be made of the following information. PRINTED IN THE NETHERLANDS Mining the Digital Information Networks v N. Lavesson et al. (Eds.) © 2013 The authors and IOS Press. This article is published online with Open Access by IOS Press and distributed under the terms of the Creative Commons Attribution Non-Commercial License. Preface The main theme of the 17th International Conference on Electronic Publishing (ELPUB) concerns different ways to extract and process data from the vast wealth of digital publishing and how to use and reuse this information in innovative social con- texts in a sustainable way.
    [Show full text]
  • Inf 212 Analysis of Prog. Langs Elements of Imperative Programming Style
    INF 212 ANALYSIS OF PROG. LANGS ELEMENTS OF IMPERATIVE PROGRAMMING STYLE Instructors: Kaj Dreef Copyright © Instructors. Objectives Level up on things that you may already know… ! Machine model of imperative programs ! Structured vs. unstructured control flow ! Assignment ! Variables and names ! Lexical scope and blocks ! Expressions and statements …so to understand existing languages better Imperative Programming 3 Oldest and most popular paradigm ! Fortran, Algol, C, Java … Mirrors computer architecture ! In a von Neumann machine, memory holds instructions and data Control-flow statements ! Conditional and unconditional (GO TO) branches, loops Key operation: assignment ! Side effect: updating state (i.e., memory) of the machine Simplified Machine Model 4 Registers Code Data Stack Program counter Environment Heap pointer Memory Management 5 Registers, Code segment, Program counter ! Ignore registers (for our purposes) and details of instruction set Data segment ! Stack contains data related to block entry/exit ! Heap contains data of varying lifetime ! Environment pointer points to current stack position ■ Block entry: add new activation record to stack ■ Block exit: remove most recent activation record Control Flow 6 Control flow in imperative languages is most often designed to be sequential ! Instructions executed in order they are written ! Some also support concurrent execution (Java) But… Goto in C # include <stdio.h> int main(){ float num,average,sum; int i,n; printf("Maximum no. of inputs: "); scanf("%d",&n); for(i=1;i<=n;++i){
    [Show full text]
  • Obfuscating C++ Programs Via Control Flow Flattening
    Annales Univ. Sci. Budapest., Sect. Comp. 30 (2009) 3-19 OBFUSCATING C++ PROGRAMS VIA CONTROL FLOW FLATTENING T. L¶aszl¶oand A.¶ Kiss (Szeged, Hungary) Abstract. Protecting a software from unauthorized access is an ever de- manding task. Thus, in this paper, we focus on the protection of source code by means of obfuscation and discuss the adaptation of a control flow transformation technique called control flow flattening to the C++ lan- guage. In addition to the problems of adaptation and the solutions pro- posed for them, a formal algorithm of the technique is given as well. A prototype implementation of the algorithm presents that the complexity of a program can show an increase as high as 5-fold due to the obfuscation. 1. Introduction Protecting a software from unauthorized access is an ever demanding task. Unfortunately, it is impossible to guarantee complete safety, since with enough time given, there is no unbreakable code. Thus, the goal is usually to make the job of the attacker as di±cult as possible. Systems can be protected at several levels, e.g., hardware, operating system or source code. In this paper, we focus on the protection of source code by means of obfuscation. Several code obfuscation techniques exist. Their common feature is that they change programs to make their comprehension di±cult, while keep- ing their original behaviour. The simplest technique is layout transformation [1], which scrambles identi¯ers in the code, removes comments and debug informa- tion. Another technique is data obfuscation [2], which changes data structures, 4 T. L¶aszl¶oand A.¶ Kiss e.g., by changing variable visibilities or by reordering and restructuring arrays.
    [Show full text]
  • Control Flow
    Control Flow The control flow of a program is the way an execution moves from statement to statement. The textbook breaks it down into: Sequencing (do the next thing) Selection (pick something to do, e.g. if , switch) Iteration (repeat something, e.g. while, for) Recursion Unstructured (e.g. goto) Roche (USNA) SI413 - Class 23 Fall 2011 1 / 12 Unstructured flow: GOTO In the beginning, there was GOTO. And GOTO was good. Directly jumps from one place (the goto) to another (the label) Corresponds exactly to machine code Very efficient Can cause some problems. Roche (USNA) SI413 - Class 23 Fall 2011 2 / 12 Good Use of Goto? Say we want to print a vector, comma-separated, like “1, 2, 3”. This solution prints an extra comma! vector< i n t >v; // ... i n t i = 0; w h i l e (i<v.size()){ cout <<v[i] << ”, ”; ++i; } cout << endl; Roche (USNA) SI413 - Class 23 Fall 2011 3 / 12 Goto Problems They don’t play well with scopes. (Restricting to local gotos avoids this.) Can be used to cook up “spaghetti code” — hard to follow. Hard to know where we are in the program, i.e., hard to reason about the program’s correctness/performance. Roche (USNA) SI413 - Class 23 Fall 2011 4 / 12 i n t x = 0; char c; goto rs; fns: i f (c != ’1’ &&c != ’0’ ) goto er; goto ns; rd: c= getchar(); ns: i f (c == ’1’ ){x=x*2 + 1; goto rd;} i f (c == ’0’ ){x=x*2; goto rd;} es: i f (c == ’ ’ ) { c= getchar(); goto es; } i f (c == ’ n’ ) goto done; er: \ printf( ”Error! n” ); r e t u r n 1; \ rs: c=getchar(); i f (c == ’ ’ ) goto rs; e l s e goto fns; done: printf( ”%i n” ,x); \ Roche (USNA) SI413 - Class 23 Fall 2011 5 / 12 Structured Programming Structured programming is probably all you have ever known.
    [Show full text]
  • Control Flow Statements
    Control Flow Statements Christopher M. Harden Contents 1 Some more types 2 1.1 Undefined and null . .2 1.2 Booleans . .2 1.2.1 Creating boolean values . .3 1.2.2 Combining boolean values . .4 2 Conditional statements 5 2.1 if statement . .5 2.1.1 Using blocks . .5 2.2 else statement . .6 2.3 Tertiary operator . .7 2.4 switch statement . .8 3 Looping constructs 10 3.1 while loop . 10 3.2 do while loop . 11 3.3 for loop . 11 3.4 Further loop control . 12 4 Try it yourself 13 1 1 Some more types 1.1 Undefined and null The undefined type has only one value, undefined. Similarly, the null type has only one value, null. Since both types have only one value, there are no operators on these types. These types exist to represent the absence of data, and their difference is only in intent. • undefined represents data that is accidentally missing. • null represents data that is intentionally missing. In general, null is to be used over undefined in your scripts. undefined is given to you by the JavaScript interpreter in certain situations, and it is useful to be able to notice these situations when they appear. Listing 1 shows the difference between the two. Listing 1: Undefined and Null 1 var name; 2 // Will say"Hello undefined" 3 a l e r t( "Hello" + name); 4 5 name= prompt( "Do not answer this question" ); 6 // Will say"Hello null" 7 a l e r t( "Hello" + name); 1.2 Booleans The Boolean type has two values, true and false.
    [Show full text]
  • Control Flow Statements in Java Tutorials Point
    Control Flow Statements In Java Tutorials Point Cnidarian and Waldenses Bubba pillar inclemently and excorticated his mong troublesomely and hereabout. andRounding convective and conversational when energises Jodi some cudgelled Anderson some very prokaryote intertwiningly so wearily! and pardi? Is Gordon always scaphocephalous Go a certain section, commercial use will likely somewhere in java, but is like expression representation of flow control for loop conditionals are independent prognostic factors In this disease let's delve deep into Java Servlets and understand when this. Java Control Flow Statements CoreJavaGuru. Loops in Java Tutorialspointdev. Advantages of Java programming Language. Matlab object On what Kitchen Floor. The flow of controls cursor positioning of files correctly for the python and we represent the location of our java entry points and times as when exploits are handled by minimizing the. The basic control flow standpoint the typecase construct one be seen to realize similar to. Example- Circumference of Circle 227 x Diameter Here This technique. GPGPU GPU Java JCuda For example charity is not discount to control utiliza- com A. There are 3 types of two flow statements supported by the Java programming language Decision-making statements if-then they-then-else switch Looping. Java IfElse Tutorial W3Schools. Spring batch passing data between steps. The tutorial in? Remove that will need to point handling the tutorial will be used or run unit of discipline when using this statement, easing the blinking effect. Either expressed or database systems support for tcl as a controlling source listing applies to a sending field identifier names being part and production.
    [Show full text]
  • Control Flow Analysis
    SIGPLAN Notices 1970 July Control Flow Analysis Frances E. Allen IBM CORPORATION INTRODUCTION Any static, global analysis of the expression and data relation- ships in a program requires a knowledge of the control flow of the program. Since one of the primary reasons for doing such a global analysis in a compiler is to produce optimized programs, control flow analysis has been embedded in many compilers and has been described in several papers. An early paper by Prosser [5] described the use of Boolean matrices (or, more particularly, connectivity matrices) in flow analysis. The use of "dominance" relationships in flow analysis was first introduced by Prosser and much expanded by Lowry and Medlock [6]. References [6,8,9] describe compilers which use various forms of control flow analysis for optimization. Some recent develop- ments in the area are reported in [4] and in [7]. The underlying motivation in all the different types of control flow analysis is the need to codify the flow relationships in the program. The codification may be in connectivity matrices, in predecessor-successor tables, in dominance lists, etc. Whatever the form, the purpose is to facilitate determining what the flow relation- ships are; in other words to facilitate answering such questions as: is this an inner loop?, if an expression is removed from the loop where can it be correctly and profitably placed?, which variable definitions can affect this use? In this paper the basic control flow relationships are expressed in a directed graph. Various graph constructs are then found and shown to codify interesting global relationships.
    [Show full text]
  • Code Based Analysis of Object-Oriented Systems Using Extended Control Flow Graph
    CORE Metadata, citation and similar papers at core.ac.uk Provided by ethesis@nitr Code Based Analysis of Object-Oriented Systems Using Extended Control Flow Graph A thesis submitted in partial fulfillment for the degree of Bachelor of Technology by Shariq Islam 109CS0324 Under the supervision of Prof. S. K. Rath DEPARTMENT OF COMPUTER SCIENCE & ENGINEERING NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA, ORISSA, INDIA-769008 May 2013 Certificate This is to certify that the thesis entitled \Code Based Analysis of Object-Oriented Systems using Extended Control Flow Graph" submitted by Shariq Islam, in the partial fulfillment of the requirements for the award of Bachelor of Technology Degree in Computer Science & Engineering at National Institute of Technology Rourkela is an authentic work carried out by him under my supervision and guidance. To best of my knowledge, The matter embodied in the thesis has not been submitted to any other university / institution for the award of any Degree or Diploma. Date: Dr. S. K. Rath ||||||||||||||||||||{ Acknowledgements I am grateful to numerous peers who have contributed toward shaping this project. At the outset, I would like to express my sincere thanks to Prof. S. K. Rath for his advice during my project work. As my supervisor, he has constantly encouraged me to remain focused on achieving my goal. His observation and comments helped me to move forward with investigation depth. He has helped me greatly and always been a source of knowledge. I am thankful to all my friends. I sincerely thank everyone who has provided me with inspirational words, a welcome ear, new ideas, constructive criticism, and their invaluable time.
    [Show full text]
  • Computer Science 2. Conditionals and Loops
    COMPUTER SCIENCE COMPUTER SCIENCE SEDGEWICK/WAYNE SEDGEWICK/WAYNE PART I: PROGRAMMING IN JAVA PART I: PROGRAMMING IN JAVA Computer Science 2. Conditionals & Loops •Conditionals: the if statement Computer 2. Conditionals and loops •Loops: the while statement Science •An alternative: the for loop An Interdisciplinary Approach •Nesting R O B E R T S E D G E W I C K 1.3 KEVIN WAYNE •Debugging http://introcs.cs.princeton.edu CS.2.A.Loops.If Context: basic building blocks for programming Conditionals and Loops Control flow • The sequence of statements that are actually executed in a program. any program you might want to write • Conditionals and loops enable us to choreograph control flow. objects true boolean 1 functions and modules statement 1 graphics, sound, and image I/O false statement 2 statement 1 arrays boolean 2 true statement 2 conditionalsconditionals and loops statement 3 Math text I/O false statement 4 statement 3 primitive data types assignment statements This lecture: to infinity and beyond! Previous lecture: straight-line control flow control flow with conditionals and a loop equivalent to a calculator [ previous lecture ] [this lecture] 3 4 The if statement Example of if statement use: simulate a coin flip Execute certain statements depending on the values of certain variables. • Evaluate a boolean expression. public class Flip • If true, execute a statement. { • The else option: If false, execute a different statement. public static void main(String[] args) { if (Math.random() < 0.5) System.out.println("Heads"); Example: if (x > y) max = x; Example: if (x < 0) x = -x; else else max = y; System.out.println("Tails"); % java Flip } Heads } true true x < 0 ? false x > y ? false % java Flip Heads x = -x; max = x; max = y; % java Flip Tails % java Flip Heads Replaces x with the absolute value of x Computes the maximum of x and y 5 6 Example of if statement use: 2-sort Pop quiz on if statements Q.
    [Show full text]