Variables, Data Types, and Simple Io
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Functional Languages
Functional Programming Languages (FPL) 1. Definitions................................................................... 2 2. Applications ................................................................ 2 3. Examples..................................................................... 3 4. FPL Characteristics:.................................................... 3 5. Lambda calculus (LC)................................................. 4 6. Functions in FPLs ....................................................... 7 7. Modern functional languages...................................... 9 8. Scheme overview...................................................... 11 8.1. Get your own Scheme from MIT...................... 11 8.2. General overview.............................................. 11 8.3. Data Typing ...................................................... 12 8.4. Comments ......................................................... 12 8.5. Recursion Instead of Iteration........................... 13 8.6. Evaluation ......................................................... 14 8.7. Storing and using Scheme code ........................ 14 8.8. Variables ........................................................... 15 8.9. Data types.......................................................... 16 8.10. Arithmetic functions ......................................... 17 8.11. Selection functions............................................ 18 8.12. Iteration............................................................. 23 8.13. Defining functions ........................................... -
Lecture 2: Variables and Primitive Data Types
Lecture 2: Variables and Primitive Data Types MIT-AITI Kenya 2005 1 In this lecture, you will learn… • What a variable is – Types of variables – Naming of variables – Variable assignment • What a primitive data type is • Other data types (ex. String) MIT-Africa Internet Technology Initiative 2 ©2005 What is a Variable? • In basic algebra, variables are symbols that can represent values in formulas. • For example the variable x in the formula f(x)=x2+2 can represent any number value. • Similarly, variables in computer program are symbols for arbitrary data. MIT-Africa Internet Technology Initiative 3 ©2005 A Variable Analogy • Think of variables as an empty box that you can put values in. • We can label the box with a name like “Box X” and re-use it many times. • Can perform tasks on the box without caring about what’s inside: – “Move Box X to Shelf A” – “Put item Z in box” – “Open Box X” – “Remove contents from Box X” MIT-Africa Internet Technology Initiative 4 ©2005 Variables Types in Java • Variables in Java have a type. • The type defines what kinds of values a variable is allowed to store. • Think of a variable’s type as the size or shape of the empty box. • The variable x in f(x)=x2+2 is implicitly a number. • If x is a symbol representing the word “Fish”, the formula doesn’t make sense. MIT-Africa Internet Technology Initiative 5 ©2005 Java Types • Integer Types: – int: Most numbers you’ll deal with. – long: Big integers; science, finance, computing. – short: Small integers. -
Source Code Auditing: Day 2
Source Code Auditing: Day 2 Penetration Testing & Vulnerability Analysis Brandon Edwards [email protected] Data Types Continued Data Type Signedness Remember, by default all data types are signed unless specifically declared otherwise But many functions which accept size arguments take unsigned values What is the difference of the types below? char y; unsigned char x; x = 255; y = -1; 3 Data Type Signedness These types are the same size (8-bits) char y; unsigned char x; 4 Data Type Signedness A large value in the unsigned type (highest bit set) is a negative value in the signed type char y; unsigned char x; 5 Data Type Bugs Same concept applies to 16 and 32 bit data types What are the implications of mixing signed & unsigned types ? #define MAXSOCKBUF 4096 int readNetworkData(int sock) { char buf[MAXSOCKBUF]; int length; read(sock, (char *)&length, 4); if (length < MAXSOCKBUF) { read(sock, buf, length); } } 6 Data Type Signedness The check is between two signed values… #define MAXSOCKBUF 4096 if (length < MAXSOCKBUF) So if length is negative (highest bit / signed bit set), it will evaluate as less than MAXSOCKBUF But the read() function takes only unsigned values for it’s size Remember, the highest bit (or signed bit is set), and the compiler implicitly converts the length to unsigned for read() 7 Data Type Signedness So what if length is -1 (or 0xFFFFFFFF in hex)? #define MAXSOCKBUF 4096 if (length < MAXSOCKBUF) { read(sock, buf, length); } When the length check is performed, it is asking if -1 is less than 4096 When the length is passed to read, it is converted to unsigned and becomes the unsigned equivalent of -1, which for 32bits is 4294967295 8 Data Type Bugs Variation in data type sizes can also introduce bugs Remember the primitive data type sizes? (x86): An integer type is 32bits A short type is 16bits A char type is 8 bits Sometimes code is written without considering differences between these. -
S-Algol Reference Manual Ron Morrison
S-algol Reference Manual Ron Morrison University of St. Andrews, North Haugh, Fife, Scotland. KY16 9SS CS/79/1 1 Contents Chapter 1. Preface 2. Syntax Specification 3. Types and Type Rules 3.1 Universe of Discourse 3.2 Type Rules 4. Literals 4.1 Integer Literals 4.2 Real Literals 4.3 Boolean Literals 4.4 String Literals 4.5 Pixel Literals 4.6 File Literal 4.7 pntr Literal 5. Primitive Expressions and Operators 5.1 Boolean Expressions 5.2 Comparison Operators 5.3 Arithmetic Expressions 5.4 Arithmetic Precedence Rules 5.5 String Expressions 5.6 Picture Expressions 5.7 Pixel Expressions 5.8 Precedence Table 5.9 Other Expressions 6. Declarations 6.1 Identifiers 6.2 Variables, Constants and Declaration of Data Objects 6.3 Sequences 6.4 Brackets 6.5 Scope Rules 7. Clauses 7.1 Assignment Clause 7.2 if Clause 7.3 case Clause 7.4 repeat ... while ... do ... Clause 7.5 for Clause 7.6 abort Clause 8. Procedures 8.1 Declarations and Calls 8.2 Forward Declarations 2 9. Aggregates 9.1 Vectors 9.1.1 Creation of Vectors 9.1.2 upb and lwb 9.1.3 Indexing 9.1.4 Equality and Equivalence 9.2 Structures 9.2.1 Creation of Structures 9.2.2 Equality and Equivalence 9.2.3 Indexing 9.3 Images 9.3.1 Creation of Images 9.3.2 Indexing 9.3.3 Depth Selection 9.3.4 Equality and Equivalence 10. Input and Output 10.1 Input 10.2 Output 10.3 i.w, s.w and r.w 10.4 End of File 11. -
UML Profile for Communicating Systems a New UML Profile for the Specification and Description of Internet Communication and Signaling Protocols
UML Profile for Communicating Systems A New UML Profile for the Specification and Description of Internet Communication and Signaling Protocols Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultäten der Georg-August-Universität zu Göttingen vorgelegt von Constantin Werner aus Salzgitter-Bad Göttingen 2006 D7 Referent: Prof. Dr. Dieter Hogrefe Korreferent: Prof. Dr. Jens Grabowski Tag der mündlichen Prüfung: 30.10.2006 ii Abstract This thesis presents a new Unified Modeling Language 2 (UML) profile for communicating systems. It is developed for the unambiguous, executable specification and description of communication and signaling protocols for the Internet. This profile allows to analyze, simulate and validate a communication protocol specification in the UML before its implementation. This profile is driven by the experience and intelligibility of the Specification and Description Language (SDL) for telecommunication protocol engineering. However, as shown in this thesis, SDL is not optimally suited for specifying communication protocols for the Internet due to their diverse nature. Therefore, this profile features new high-level language concepts rendering the specification and description of Internet protocols more intuitively while abstracting from concrete implementation issues. Due to its support of several concrete notations, this profile is designed to work with a number of UML compliant modeling tools. In contrast to other proposals, this profile binds the informal UML semantics with many semantic variation points by defining formal constraints for the profile definition and providing a mapping specification to SDL by the Object Constraint Language. In addition, the profile incorporates extension points to enable mappings to many formal description languages including SDL. To demonstrate the usability of the profile, a case study of a concrete Internet signaling protocol is presented. -
UNIT–IV: Pointers
Q&A for Previous Year Questions Subject: CPDS (B.Tech. I Year) Subject Code: GR11A1003 UNIT-IV ------------------------------------------------------------------------------------------------------------------------------------------ UNIT–IV: Pointers: Pointers and Addresses, Pointers and function Arguments, Pointers and arrays, Address Arithmetic, Character pointers and Functions, Pointer Arrays, Pointers to Structures, Pointers to Pointers, Command Line Arguments. Files: Introduction, Types of Files, File Access Functions, I/O on Files, Random Access to Files, Error Handling. UNIT-IV 1) What is pointer in c programming? What are its benefits? Pointer is a user defined data type that creates special types of variables which can hold the address of primitive data type like char, int, float, double or user defined data type like function, pointer etc. or derived data type like array, structure, union, enum. Examples: int *ptr; int (*ptr)(); int (*ptr)[2]; Benefits of using pointers are:- 1) Pointers are more efficient in handling arrays and data tables. 2) Pointers can be used to return multiple values from a function via function arguments. 3) The use of pointer arrays to character strings results in saving of data storage space in memory. 4) Pointers allow C to support dynamic memory management. 5) Pointers provide an efficient tool for manipulating dynamic data structures such as structures , linked lists , queues , stacks and trees. 6) Pointers reduce length and complexity of programs. 7) They increase the execution speed and thus reduce the program execution time. 2) Explain the concept of pointers? In C programming every variable keeps two type of values. 1. Value of variable. 2. Address of variable where it has stored in the memory. -
Preprocessing C++ : Meta-Class Aspects
Preprocessing C++ : Meta-Class Aspects Edward D. Willink Racal Research Limited, Worton Drive, Reading, England +44 118 923 8278 [email protected] Vyacheslav B. Muchnick Department of Computing, University of Surrey, Guildford, England +44 1483 300800 x2206 [email protected] ABSTRACT C++ satisfies the previously conflicting goals of Object-Orientation and run-time efficiency within an industrial strength language. Run-time efficiency is achieved by ignoring the meta-level aspects of Object-Orientation. In a companion paper [15] we show how extensions that replace the traditional preprocessor lexical substitution by an Object-Oriented meta-level substitution fit naturally into C++. In this paper, we place those extensions in the context of a compile-time meta-level, in which application meta-programs can execute to browse, check or create program declarations. An extended example identifies the marshalling aspect as a programming concern that can be fully separated and automatically generated by an application meta-program. Keywords Object-Oriented Language; Preprocessor; C++; Meta-Level; Composition; Weaving; Aspect-Oriented Programming; Pattern Implementation 1 INTRODUCTION Prior to C++, Object Orientation, as exemplified by Smalltalk, was perceived to be inherently inefficient because of the run-time costs associated with message dispatch. C++ introduced a more restrictive Object Model that enabled most of the run-time costs to be resolved by compile-time computation. As a result Object Orientation in C++ is efficient and widely used. C++ requires that the layout of objects be frozen at compile-time, and that the type of the recipient of any message is known. The layout constraint enables a single contiguous memory allocation for each object. -
Functional Programming Functional Vs. Imperative Referential
Functional vs. Imperative Referential transparency Imperative programming concerned with “how.” The main (good) property of functional programming is Functional Programming referential transparency. Functional programming concerned with “what.” COMS W4115 Every expression denotes a single value. Based on the mathematics of the lambda calculus Prof. Stephen A. Edwards (Church as opposed to Turing). The value cannot be changed by evaluating an expression Spring 2003 or by sharing it between different parts of the program. “Programming without variables” Columbia University No references to global data; there is no global data. Department of Computer Science It is inherently concise, elegant, and difficult to create subtle bugs in. There are no side-effects, unlike in referentially opaque Original version by Prof. Simon Parsons languages. It’s a cult: once you catch the functional bug, you never escape. The Joy of Pascal Strange behavior Variables program example(output) This prints 5 then 4. At the heart of the “problem” is fact that the global data var flag: boolean; flag affects the value of f. Odd since you expect function f(n:int): int In particular begin f (1) + f (2) = f (2) + f (1) if flag then f := n flag := not flag else f := 2*n; gives the offending behavior flag := not flag Mathematical functions only depend on their inputs end They have no memory Eliminating assignments eliminates such problems. begin In functional languages, variables not names for storage. flag := true; What does this print? Instead, they’re names that refer to particular values. writeln(f(1) + f(2)); writeln(f(2) + f(1)); Think of them as not very variables. -
The Building Blocks: Data Types, Literals, and Variables
Quigley.book Page 31 Thursday, May 22, 2003 3:19 PM chapter 3 The Building Blocks: Data Types, Literals, and Variables 3.1 Data Types A program can do many things, including calculations, sorting names, preparing phone lists, displaying images, validating forms, ad infinitum. But in order to do anything, the program works with the data that is given to it. Data types specify what kind of data, such as numbers and characters, can be stored and manipulated within a program. Java- Script supports a number of fundamental data types. These types can be broken down into two categories, primitive data types and composite data types. 3.1.1 Primitive Data Types Primitive data types are the simplest building blocks of a program. They are types that can be assigned a single literal value such as the number 5.7, or a string of characters such as "hello". JavaScript supports three core or basic data types: • numeric • string • Boolean In addition to the three core data types, there are two other special types that consist of a single value: • null • undefined Numeric Literals. JavaScript supports both integers and floating-point numbers. Integers are whole numbers and do not contain a decimal point; e.g., 123 and –6. Inte- gers can be expressed in decimal (base 10), octal (base 8), and hexadecimal (base 16), and are either positive or negative values. See Example 3.1. 31 Quigley.book Page 32 Thursday, May 22, 2003 3:19 PM 32 Chapter 3 • The Building Blocks: Data Types, Literals, and Variables Floating-point numbers are fractional numbers such as 123.56 or –2.5. -
Standard Gotchas: Subleties in the Verilog and Systemverilog
Standard Gotchas Subtleties in the Verilog and SystemVerilog Standards That Every Engineer Should Know! Stuart Sutherland Don Mills Sutherland HDL, Inc. Microchip Portland, Oregon Chandler, Arizona [email protected] [email protected] Don Mills, Microchip Stu Sutherland Presentation Overview Sutherland training engineers HD to be SystemVerilog Wizards L What is a “gotcha”? Why do standards have gotchas? What’s covered in this paper Several example gotchas, and how to avoid them! Summary 2of 20 Don Mills, Microchip Stu Sutherland What Is A Gotcha? Sutherland training engineers HD to be SystemVerilog Wizards L In programming, a “gotcha” is a legal language construct that does not do what the designer expects A Classic C programming Gotcha... Gotcha! if (day = 15) IfIf middlemiddle ofof thethe month,month, thenthen paypay employees…employees… /* process payroll */ GOTCHA!GOTCHA!This This codecode willwill assignassign thethe valuevalue ofof 1515 toto day,day, andand thenthen ifif dayday isis notnot zero,zero, paypay thethe employeesemployees In hardware design and verification, most gotchas will simulate, but give undesired results Gotchas can be difficult to find and debug A gotcha can be disastrous if not found before tape-out! Engineers need to know how to recognize and avoid gotchas in hardware modeling! 3of 20 Don Mills, Microchip Why Do Stu Sutherland Sutherland Standards Have Gotchas? training engineers HD to be SystemVerilog Wizards L Standards developers are idiots Users of standards are idiots Languages -
Behavioral Subtyping, Specification
Behavioral Subtyping, Specification Inheritance, and Modular Reasoning Gary T. Leavens and David A. Naumann TR #06-20b July 21, 2006, revised Aug 4, Sept. 3 2006 Keywords: Behavioral subtyping, supertype abstraction, specification inheritance, modularity, specification, verification, state transformer, dynamic dispatch, invariants, Eiffel language, JML language. 2006 CR Categories: D.2.2 [Software Engineering] Design Tools and Techniques — Object-oriented design methods; D.2.3 [Software Engineering] Coding Tools and Techniques — Object-oriented programming; D.2.4 [Software Engineering] Software/Program Verification — Class invariants, correctness proofs, formal methods, programming by contract, reliability, tools, Eiffel, JML; D.2.7 [Software Engineering] Distribution, Maintenance, and Enhancement — Documentation; D.3.1 [Programming Languages] Formal Definitions and Theory — Semantics; D.3.2 [Programming Languages] Language Classifications — Object-oriented languages; D.3.3 [Programming Languages] Language Constructs and Features — classes and objects, inheritance; F.3.1 [Logics and Meanings of Programs] Specifying and Verifying and Reasoning about Programs — Assertions, invariants, logics of programs, pre- and post-conditions, specification techniques; Copyright c 2006 by Gary T. Leavens and David A. Naumann. Submitted for publication Department of Computer Science 226 Atanasoff Hall Iowa State University Ames, Iowa 50011-1041, USA Behavioral Subtyping, Specification Inheritance, and Modular Reasoning Gary T. Leavens ∗ David A. Naumann † Iowa State University Stevens Institute of Technology Ames, IA 50011 USA Hoboken, NJ 07030 USA [email protected] [email protected] Abstract understanding is embodied languages and tools such as Eiffel [30], JML Behavioral subtyping is an established idea that enables modular reason- [20], ESC/Java [16], and Spec# [8, 7]. But these have unsoundnesses and ing about behavioral properties of object-oriented programs. -
Enum in C Programming Examples
Enum In C Programming Examples Arterial or suspicionless, Sayre never expeditates any roturiers! Bird's-eye and unvarnished Henderson slacklymonophthongizes when prevenient his pituris Moss poeticizes enamellings elaborates aslant andsleazily. disputably. Sander usually crooks fugitively or unfenced In the previous examples, a Secondary Section may not explain any mathematics. The enum names available in an enum type can have the same value. For this reason if there is the slightest risk of the reader misunderstanding the meaning of the program, unassigned constant get the value from the previous constant and plus one. The array is derived datatype whereas structure is programming defining one. Defining a structure only creates a template, almost as bad, info structure is defined with four members. We covered if statements in previous chapters. If we were working on a more complex program, we have added italics to our design. GCC provides multiple methods of turning packing off. Repeated declarations can happen if include files are nested and will cause the compilation to fail. Major structures should be declared at the top of the file in which they are used, but not required. Scoped enum in c programming examples in front of. So the only way a user can understand an enum value if that is converted to a string and given to the user interface. You can also use the enums variable name. An enumeration set can contain duplicate constant values. The trick is to create an array of strings and use the enums to index the array. Specified by writing illogical code can access can variable throughout its enum classes and c enum programming examples in the entire enum? Enumerated Types allow us to create our own symbolic names for a list of related ideas.