Reference variable in c++ pdf

 

 

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There is another variable that C++ supports, i.e., references. It is a variable that behaves as an alias for another variable. How to create a reference? Reference can be created by simply using an ampersand (&) operator. When we create a variable, then it occupies some memory location. In C++, all the variables must be declared before use. Rules For Declaring Variable: 1.The name of the variable contain letters, digits, and underscores. 2.The name of the variable are case sensitive ( ex Arr and arr both are different variable). 3.The name of the variable does not contain any whitespace and special charachters (ex #,$,%,* etc). When reference variables are used as formal parameters, this is known as Pass By Reference. void Func2 (int& x, double& y) { x = 12; // these WILL affect the original arguments y = 20.5; } When a function expects strict reference types in the parameter list, an L-value (i.e. a variable, or storage location) must be passed in. variables that are arguments to the function •Recall that we have changed the values of formal parameters in a function body, but we have not changed the arguments found in the function call •Call-by-reference parameters allow us to change the variable used in the function call -Arguments for call-by-reference parameters must Reference is an alias or another name for a variable. Given a variable with an identifier, we can provide another identifier to this variable so that we can refer to this variable either with its original name or another name. This 'another name' is what is called as a Reference. Consider we have a variable 'i' with value 17. 2.1 The Parts of a C++ Program 27 2.2 The cout Object 31 2.3 The #include Directive 36 2.4 Variables and Literals 37 2.5 Identifiers 41 2.6 Integer Data Types 42 2.7 The char Data Type 47 2.8 Floating-Point Data Types 52 2.9 The bool Data Type 55 2.10 Determining the Size of a Data Type 56 2.11 Variable Assignments and Initialization 57 2.12 Call by reference. 1. A copy of value is passed to the function. An address of value is passed to the function. 2. Changes made inside the function is not reflected on other functions. Changes made inside the function is reflected outside the function also. 3. Actual and formal arguments will be created in different memory location. Variable Argument Lists <stdarg.h> declaration of pointer to arguments va_list name; initialization of argument pointer va_start(name,lastarg) lastarg is last named parameter of the function access next unamed arg, update pointer va_arg(name,type) call before exiting function va_end(name) StandardUtilityFunctions <stdlib.h> absolute value of C++ Strings Original handout written by Neal Kanodia and Steve Jacobson. C++ Strings One of the most useful data types supplied in the C++ libraries is the string. A string is a variable that stores a sequence of letters or other characters, such as "Hello" or "May 10th is my birthday!". Just like the other data types, to create a string we ILE C/C++ Language Reference 7.1 SC09-7852-02 IBM. IBM i W ebsphere Development Studio ILE C/C++ Language Reference 7.1 SC09-7852-02 IBM. Note! Initialization of automatic variables . 75 Initialization of static variables .. . 75 Initialization of external variables . . 76 C++ vs. Java: differences C++ Java Write once, compile everywhere unique executable for each target Write once, runanywhere same class files will run above all target-specific JREs. Nostrict relationship between class names and filenames. Typically, a header file and implementation file are used for each class. machine address of an object (or variable), and does not impose performance overhead compared to pointers. The notation . X& means "reference to . X ". • Differences between reference and pointer. 1. A reference can be accessed with exactly the same syntax as the name of an object. 2. A reference always refers to the object to which it machine address of an object (or variable), and does not impose performance overhead compared to pointers. The notation . X& means "reference to . X ". • Differences between reference and pointer. 1. A reference can be accessed with exactly the same syntax as the name of an object. 2. A reference always refers to the object to which it What's a C++ reference ( for C programmers) A reference can be thought of as a constant pointer (not to be confused with a pointer to a constant value!) with automatic indirection, ie the compiler will apply the * operator for you. All references must be initialized with a non-null value or compilation will fail.

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