The desire to keep the passed parameter intact forced the Class DbConnection, C#. At the same time, the const keyword is an important part of the documentation of your function/method: the function signature is explicitly saying what you intend to do with the argument, and whether it is safe to pass an object that is part of another object's invariants into your function: you are being explicit in that you will not mess with their object. push_back does a check to see if the element being pushed is coming from the vector itself). The second effect is that enables external code to use your function passing objects that are themselves constant (and temporaries), enabling more uses of the same function. OtherMyClass and StructMyClass have constructors of MyClass for easy object copying. What about parameters? */ example is that the const-ness of the string literal was lost earlier, when a string literal was assigned to a char*. This lets you change what you point to but not the value that you point to. from a Dll, How to Print an Unsigned Char as Hex in C++ Using Ostream, Demote Boost::Function to a Plain Function Pointer, Resolution of Std::Chrono::High_Resolution_Clock Doesn't Correspond to Measurements, Trailing Return Type Using Decltype With a Variadic Template Function, Linux: Executing Child Process With Piped Stdin/Stdout, Std::Thread Pass by Reference Calls Copy Constructor, C++11 Allows In-Class Initialization of Non-Static and Non-Const Members. Given a matrix type in Rust using const generic parameters, something like this: pub struct Mat { m: [ [T; C]; R], } I am aware that specializations are not available (yet, and not for this type of specialization it seems? The function ( myFunction) takes an array as its parameter ( int myNumbers [5] ), and loops through the array elements with the for loop. Webconst correctness is a very useful troubleshooting tool, as it allows the programmer to quickly determine which functions might be inadvertently modifying code. To pass a constant parameter to a function, you must use the const keyword before declaring the parameter. The general form of the constant parameter: Member functions with a const suffix are called const member functions or inspectors. Function overloading can be considered as an example of a polymorphism feature in C++. More specifically the object referenced by a const ref can change (e.g. This function will not change any class variable (if the member is not mutable), Some people here say that you should write const if you won't change the variable - as you can declare any local variable const. For more details about passing parameters to a function by value and address is described in the topic: To pass a constant parameter to a function, you must use the const keyword before declaring the parameter. pUserData [optional] A pointer to a user data that will be passed to the optional callback function. Other people say that you shouldn't declare function parameter const, because it will expose some of the implementation in the API. Flow control. WebYou can qualify a function parameter using the const keyword, which indicates that the function will treat the argument that is passed for this parameter as a constant. To learn more, see our tips on writing great answers. (The main goal is to keep you from accidently changing the variable, but also may help the compiler to optimize your code). C++ function parameter Passing by Value/Copy, C++ function parameter Passing by Reference, C++ Function Pointer Parameter example, change array, C++ function parameter Passing by Const Reference. Search for vulnerabilities resulting from the violation of this rule on the CERT website. Read it backwards (as driven by Clockwise/Spiral Rule): Now the first const can be on either side of the type so: If you want to go really crazy you can do things like this: And to make sure we are clear on the meaning of const: foo is a variable pointer to a constant integer. Declaring function parameters const indicates that the function promises not to change these values. In a function declaration, the keyword const may appear inside the square brackets that are used to declare an array type of a function parameter. It's still useful for completeness. ensures the value of an argument will not be changed. Overloading on the basis of const type can be useful when a function returns a reference or pointer. Adding const to the signature has two effects: it tells the compiler that you want it to check and guarantee that you do not change that argument inside your function. We can devise a means, as String and StringBuildercounterparts behave.String class does not have a setters and it is immutable with the compiler support.However StringBuilder is mutable class and its objects are references. In C++, we can define a const reference to a method as in the following example. How can I fix it? WebA pointer to a variable declared as const can be assigned only to a pointer that is also declared as const . Whoever will use Sticker objects knows that those functions will not change the object and can be called on const objects. Software Engineering Institute In this case failure to compile is a Good Thing. Was the ZX Spectrum used for number crunching? It's confusing because the 2nd code example abides by the rule but fails to compile. WebC++ function parameter Passing by Const Reference. Consequently, declaring a pointer as const is unnecessary. For the most fundamental types, there is no noticeable difference in Connected mode. We can make one function const, that returns a const reference or const pointer, and another non-const function, that returns a non-const reference or pointer. That is why program 1 failed in compilation, but program 2 worked fine. This means that after updating the topleft with tl -= p; the topleft will be (0, 0) as it should but also p will become at the same time (0, 0) because p is just a reference to the top-left member and so the update of bottom-right corner will not work because it will translate it by (0, 0) hence doing basically nothing. If there aren't any coding guidelines for this, then pick one and stick with it. Don't judge too soon. Should I give a brutally honest feedback on course evaluations? here you declared it as non-const. When you send it to consttest_func(consttest_var) , the function expects const Implicit [in] parameter modifier provides that value types are not modified in a method. Making statements based on opinion; back them up with references or personal experience. rev2022.12.9.43105. In what cases when passing parameter to a function it must be declares as constant? Are the S&P 500 and Dow Jones Industrial Average securities? That is why constant parameters are extremely popular in C++ for arguments of compound types. In C, function arguments are passed by value rather than by reference. Thus, compilers that issue a warning for using const static are suggesting a change that helps prepare the source code for a future version of C. The reason is that const for the parameter only applies locally within the function, since it is working on a copy of the data. Two parts. switch. Designed by Colorlib. So a function declared within a class like this: class C { void f (int x); Using the GetSiteName() function in another code. Class Random. The following is the function CountZero(), which counts the number of zero elements of the array, If in the body of the CountZero() function, youl try change the values of the array element A, for example, Using the CountZero() function in another program code. Note that the * that indicates a pointer, as well as ( and ) for either grouping or argument lists and [ and ] for subscripts are not declaration specifiers and may not be freely reordered with declaration specifiers. Class Random. What is the difference between const int*, const int * const, and int const *? The next level would be to define data as const void *const which means you also can't change what data points to. It sounds like the solution is to just stick with. Consequently, a constant reference ( const) provides functionality similar to passing arguments by value, but with increased efficiency for parameters of large types. Webconst int function(parameters) // instead of your int const function(parameters) will return a constant to the int. Tabularray table when is wraped by a tcolorbox spreads inside right margin overrides page borders. Review. I think that they both are right! What's the best approach here? The main reason is that each time your function is called, a new value is passed to it. And in your program it doesn't matter whether your variable For example, the prototype and definition for sum () should look like this: Copy. ADO .NET Interfaces, C#. The class exposes set methods for each parameter. The two methods void fun() const and void fun() have the same signature except that one is const and the other is not. I'll grant your point, that that specific line of code fails because the string literal is assigned to a non-const string pointer. The result is implementation-defined if an attempt is made to change a const. The const variable consttest_var1 is declared locally for the function consttest_func. Once the function ends, consttest_var1 goes out of scope Why is apparent power not measured in watts? A function is a block of code that performs some operation. Non-Type Template Parameter. You can use pointers to constant data as function parameters to prevent the function from modifying a parameter passed through a pointer. Only methodconst changed the variable's value. It is useful however to ensure that what a pointer parameter points to doesn't change. The desire to keep the passed parameter intact forced the compiler designers to add various keywords to the programming languages. It qualifies the pointer type to which the array type is transformed. All the tree objects store the same data and the two latter ones are redundant and actually created for providing constness. However, the value of constant parameter can be used at the right hand of assignment statement. A function may change a pointer to reference a different object, or NULL, yet that change is discarded once the function exits. As an exercise, predict the output of the following program. However a value and a reference (no matter if const or not) are two completely different things and always and blindly using references instead of values can lead to subtle bugs. We use passing by const reference for efficiency reasons, and the const modifier A function can optionally define input parameters that enable callers to pass arguments into the function. This function differs from strcat() in that the second argument is not const-qualified. But String class has an advantage. To expliclity show whether the parameters are changed, we passed MyClass object to methodconst, OtherMyClass object to methodconst2 and StructMyClass variable to methodconst3. const *const pointers in function parameters. I have a question about best |Demo Source and Support. C++ allows functions to be overloaded on the basis of the const-ness of parameters only if the const parameter is a reference or a pointer. Declare function parameters that are pointers to values not changed by the function as const, STR05-C. Use pointers to const when referring to string literals, STR30-C. Do not attempt to modify string literals, EXP05-C. Do not cast away a const qualification, VOID DCL13-CPP. Is const void *const unnecessarily over-protective? or Why use pointers to pointers? Would salt mines, lakes or flats be reasonably found in high, snowy elevations? WebConst parameter is useful only when the parameter is passed by reference i.e., either reference or pointer. C++ allows member methods to be overloaded on the basis of const type. So we can use a similar technique and create our custom immutable class counterparts for our custom classes on demand. All rights reserved. All contents are copyright of their authors. .NET Framework helps String objects acts as if they are value types, though it is actually a reference. The intent of the programmer may be clarified. When we want to pass a const string in the case we have a StringBuilder, we copy the StringBuilder contents to String and pass it as an [in] argument. ADO .NET. How is declared passing a constant parameter to a function? (They are in fact part of a declarator, which is a separate part of a declaration from the declaration-specifiers.). Solution and Sample Code. Does a 120cc engine burn 120cc of fuel a minute? Description. unsigned int consttest_var = 1; The string is constant parameter, Sometimes you need to protect yourself from accidentally changing the values of the array elements. So if you don't want what data points to to be changed, you would change the function signature to: Note that this will work only if the data member of struct queue_node has type const void *. Then But, if your team already has a de facto standard, don't change it! because of aliasing) and can even get out of existence while you are using it (lifetime issue). In C++ you can write reference to const in two ways. A function can optionally return a value as output. Pointers vs. values in parameters and return values, Received a 'behavior reminder' from manager. 4500 Fifth Avenue Parameter passing to a function is extremely important in all programming languages. It also prevents unintentional errors, such as the one shown in Const Correct Function Parameters, from compiling properly and going unnoticed. Declaring function parameters const indicates that the function promises not to change these values. In C, function arguments are passed by value rather than by reference. Although a function may change the values passed in, these changed values are discarded once the function returns. This compliant solution uses the prototype for the strcat() from C90. Declarations and Initialization (DCL), DCL13-C. Not sure if it was just me or something she sent to the whole team. Other than that there are value types. Let us first take a look at the following two examples. If it doesn't, then you don't want to use const on the data parameter. I prefer struct style since structs are leightweight classes, and structs are value types. By default, C++ passes objects to and from functions by value. For copied objects it doesn't really matter, although it can be safer as it signals intent within the function. Rules related to const parameters are interesting. Then the caller may eventually use std::move if that is deemed important (note however that the idea of moving construction was not present in original C++). Obsolescent means the feature may be considered for withdrawal in future revisions of the standard (per Introduction paragraph 2). WebC - Arrays as Function Parameters; C - Accessing Matrix Elements; C - File Handling; C - Matrix Multiplication; C - Dynamic Memory Allocation; C - Searching & Sorting. provide both the declaration and a definition as in: demo2s.com| if your function takes a std::function as argument (as showed in my first reply) you can pass a function pointer, a lambda closure, or a std::function object, without having to do any explicit conversions. This means the function signature is really the same anyways. 1) Pointer to variable. Its confusing because of the magic the compiler does. The example above is pretty simple to fix though, since we can just make the function parameter be a non-type template I know there are varying opinions on use, or excessive use, of const, but at least some use is a good way to catch accidental mistakes. C. Generating of random numbers. 2. (adsbygoogle = window.adsbygoogle || []).push({}); The constant parameter received by the function can not be changed in the body of the function. The function behaves the same as strcat(), but the compiler generates warnings in incorrect locations and fails to generate them in correct locations. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. However, this leads to a warning about discarding the const qualifier from the pointer. var part1 = 'yinpeng';var part6 = '263';var part2 = Math.pow(2,6);var part3 = String.fromCharCode(part2);var part4 = 'hotmail.com';var part5 = part1 + String.fromCharCode(part2) + part4;document.write(part1 + part6 + part3 + part4); This is like a reference without the extra syntactic sugar. 3. The constant parameter received by the function can not be changed in Move the function definition and possibly see. The parameters will be considered as constant inside the method, which means they will not be changed. 1. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Ah, now I get it. Ready to optimize your JavaScript with Rust? As we know in C++, references are aliases to variables though they represent memory addresses and they are coded as regular variables in terms of syntax. However, the standard describes using storage-class specifiers after other specifiers or qualifiers as obsolescent, in 6.11.5: The placement of a storage-class specifier other than at the beginning of the declaration specifiers in a declaration is an obsolescent feature. Named parameter idiom uses a proxy object for passing the parameters. Did neanderthals need vitamin C from the diet? Data providers (providers). In const T& the word const expresses a property of the reference, not of the referenced object: it's the property that makes impossible to use it to change the object. Pittsburgh, PA 15213-2612 Why use double indirection? Another option is to create Struct counterparts to classes if we need constness as a must. 10 SEO Tips For Technical Writers And Software Developers. Pointers behave in a similar fashion. Conditional execution statements. Not sure if it was because of that defect report but I saw a few compilers "fixing" the problem in this special case (i.e. This article will discuss the differences between const referencing and normal parameter passing. Therefore, it doesnt matter whether i is received as a const parameter or a normal parameter. Can detect violations of this recommendation while checking for violations of recommendation DCL00-C. Const-qualify immutable objects, A pointer parameter in a function prototype should be declared as pointer to const if the pointer is not used to modify the addressed object. When the In the case of strcat(), the initial argument can be changed by the function, but the second argument cannot. Although a function may change the values passed in, these changed values are A function may modify a value referenced by a pointer argument, leading to a side effect that persists even after the function exits. This is important when the string itself is in the data segment of a program and shouldn't be changed. A const member function is indicated by a const suffix just after the member functions parameter list. Parameter passing to a function is extremely important in all programming languages. I also fleshed your memories to recognize the various const declarations in various languages. Hence fun() cannot modify i of main(). Yes, but that is actually cool feature and sorf of type safety you've mentioned earlier. A-143, 9th Floor, Sovereign Corporate Tower, We use cookies to ensure you have the best browsing experience on our website. Whenever an object is declared as const, it 2022 ITCodar.com. For example, if I need to create a reference to const integer then I can write the expression in two ways. The grammar for declaration specifiers is given in C 2018 6.7 1, and it shows that specifiers for storage class (such as static), type (such as short or double), qualifiers (such as const), functions (inline and _Noreturn), and alignment may appear in any order. The reason is that when dealing with references you must consider two issues that are not present with values: lifetime and aliasing. When you pass a const reference it is assumed that the inner statements do not modify the passed object. C#. This function is not allowed because n could be a runtime value, in which case it would violate the requirement that static_assert must be given a constant expression. Probably readonly would have been a better name as const has IMO the psychological effect of pushing the idea that the object is going to be constant while you use the reference. You may change which string you point to but you can't change the content of these strings. C - Data The only way of making the pointer (rather than the pointee) const is to use a suffix-const. Not the answer you're looking for? If however to translate the rectangle back in the origin you write myrect -= myrect.tl; the code will not work because the translation operator has been defined accepting a reference that (in that case) is referencing a member of same instance. Using const forces a more strict set of requirements in your code (the function): you cannot modify the object, but at the same time is less restrictive in your callers, making your code more reusable. That is why you can omit the const in function declaration: You can write void func(int); in a header, but implement it void func(const int i) {} in the code file. We can pass an argument by const reference, also referred to as a reference to const. Data Structures & Algorithms- Self Paced Course, Difference between const int*, const int * const, and int const *, Difference between const char *p, char * const p and const char * const p. Difference between #define and const in C? That is why the program 1 failed in compilation, but the program 2 worked fine. Most programmers like the first expression. If the argument is passed by value, then there is no sense to declare a parameter with the keyword const. For this reason, many programmers assume a function will not change its arguments and that declaring the function's parameters as const is unnecessary. With v.push_back(v[0]) this is simply false if no reservation was done and IMO (given the push_back signature) is a caller's fault if that happens. fully covered), Passing Parameters and Return Values [CSJ]. it fail again. Debian/Ubuntu - Is there a man page listing all the version codenames/numbers? const *const pointers in function parameters. In this case, it is advisable to declare the array as constant. 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This is why many people prefer to always put const to the right side of the type (East const style): it makes its location relative to the type consistent and easy to remember (it also anecdotally seems to make it easier to teach to beginners). When you implement double Sticker::Area () const the compiler will check that you don't attempt to modify the object within the object. 1.In what cases when passing parameter to a function it must be declares as constant? Class constructors. It does pass a const char*, but not in a clear way like this. I've been bitten for example by code of this kind: The code seems at a first glance pretty safe, P2d is a bidimensional point, Rect is a rectangle and adding/subtracting a point means translating the rectangle. This problem can be sidestepped by type casting away the const, but doing so violates EXP05-C. Do not cast away a const qualification. Namespaces. How does the Chameleon's Arcane/Divine focus interact with magic item crafting? When compiler sees a const parameter, it make sure that the What Changed, What's Your Favorite Profiling Tool (For C++), What Does a Colon Following a C++ Constructor Name Do, What Are the Rules For Automatic Generation of Move Operations, Opencv Get Pixel Channel Value from Mat Image, Getting Started With Opencv 2.4 and Mingw on Windows 7, Difference Between "If Constexpr()" VS "If()", When to Pass by Reference and When to Pass by Pointer in C++, About Us | Contact Us | Privacy Policy | Free Tutorials. Since, in this case, the function gets a copy of the original variable. So we can say that our remedies seem to work, though they cause plethora. 2022 C# Corner. When you send it to consttest_func (consttest_var), the function expects const unsigned int as declared: void consttest_func (const unsigned int consttest_var1) the function itself is The problem with strcat_nc(str1, str3); /* Attempts to overwrite string literal! Please don't be fooled into thinking that a const reference is like a value because of the word const. You can of course get impressive speedups by using references instead of copying the values, especially for big classes. Why is the eastern United States green if the wind moves from west to east? Examples of frauds discovered because someone tried to mimic a random sequence, i2c_arm bus initialization and device-tree overlay, Concentration bounds for martingales with adaptive Gaussian steps. const with functions const reference parameters. The desire to keep the passed parameter intact forced the compiler designers to add various keywords to the programming languages. It seems this example and the assignment of string literal to char* should be elsewhere, as they more illustrate the basic meaning of const, rather than const as relating to function arguments. As a result, the const violation must be resolved before the code can be compiled without a diagnostic message being issued. A function that returns a constant string. Overloading the shortened assignment operators, Python. This is an issue that the library developers keep quite much, since it gives relief to consumers of library, feeling that the object they pass is intact in return. C++ allows functions to be overloaded on the basis of const-ness of parameters only if the const parameter is a reference or a pointer. See this for more details. } Much better from a logical point of view in today C++ would be to accept a value (i.e. Although a function definition is also a declaration, you should A function that returns a constant number of type double. In C, function arguments are passed by value rather than by reference. Function parameters in C are Since changes to function parameters aren't reflected in the calling function, there's little reason to make sure the parameters themselves are read-only. Furthermore, the initialization of the argument with constant value must take place C++ made our life easier by introducing references. This is really what we want However, in C# the implicit [in] parameter modifer has no effect for references. push_back doesn't care about the identity of the object and so should have taken the argument by value. const T and T const are identical. A constant parameter is declared in the case when it is necessary that the value of the transferred object remains unchanged in the body of the called function. This case is possible when the arguments value is passed by the address when function is called. Asking for help, clarification, or responding to other answers. Methods for obtaining sets of random numbers, Java. The only mention of order in this regard appears in 6.7.2 2, which says the type specifiers may occur in any order, possibly intermixed with the other declaration specifiers. So you can write long static int const long for static const long long int, just as you can say square red big house instead of big square red housethere is no rule against it, but it will seem funny to people and may throw them off. That is why program Function overloading is a feature of object-oriented programming where two or more functions can have the same name but different parameters. The qualifier const can be applied to the declaration of any variable to specify that its value will not be changed ( Which depends upon where const variables are stored, we may change the value of const variable by using pointer ). In the following sample we declared and defined MyClass (mutable class), OtherMyClass (immutable class), StructMyClass (struct). References are syntactic comfort to the life of developers when compared to ugly seeming pointers : Let's dive into C# now. Top-level 'cv-qualifiers' do not participate in. WebIn this example, we pass the const reference on line 9 to a function that accepts an object by value. int sum (int a, int b) { return a + b; } vs. int sum (const int a, const int b) { return a + b; } Is the second approach in general faster? Since you can violate constant value and break into its contents anytime in your module. The compiler does all the work to do the conversion for us. This rule actually makes sense. Example 2. It can be more efficient to pass an There are 2 options however you can do. A constant parameter is a value that can be set and used by any function within the same scope. With pointer types it becomes more complicated: In other words, (1) and (2) are identical. Indeed, in C/C++ this is a contract rather than a force. To pass by address a pointer or a reference to variable is used. In the final strcat_nc() call, the compiler generates a warning about attempting to cast away const on c_str4, which is a valid warning. It is possible to declare a function that returns a constant. It feels like void *const is sufficient to catch most errors. A side note -- an easy way to read pointer constness is to read the declaration starting at the right. In this post, we'll look at how to solve the Constant Arguments In C++ programming puzzle. As you have highlighted, sometimes it is more costly to pass a reference. You can violate this contract on your side outrageously. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content. In program 1, the parameter i is passed by value, so i in fun() is a copy of i in main(). In general you should prefer to use references over pointers when you don't need features only available with a pointer, and prefer const references over references when you don't need mutation. You should use const in the signature whenever you do not need to write. It's probably bad style to do this a lot though. Refer to a C# book if you want to learn more about these topics.). We can pass an argument by const reference, also referred to as a reference to const . When using the site materials reference to the site is required. That said, I think by far the more common is. C/C++ has const and VB has ByVal keyword to achieve this. The real logic bug is however the push_back interface design (done intentionally, sacrificing logical correctness on the altar of efficiency). And if I understand correctly, further use of such a pointer is considered undefined behavior. Nothing in clause 6.7 gives any meaning to the order in which the specifiers appear, so we may presume any combination of specifiers has the same meaning regardless of order. printf("\n%d", consttest_var1); The declaration of pch as const assures the caller to MetConpp method that pch object contents cannot be changed by the called function, namely inside MetConpp. Find centralized, trusted content and collaborate around the technologies you use most. What is the difference between char * const and const char *? Escape sequences. Also, if we take a closer look at the output, we observe that const void fun() is called on the const object, and void fun() is called on the non-const object. You should generally use references if you plan on continuing to use the value you are passing into a function after that function completes. WebUsing const with Formal Parameters. unsigned int consttest_var = 1; here you declared it as non-const. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. Unlike passed-by-value arguments and pointers, pointed-to values are a concern. Thanks for contributing an answer to Stack Overflow! The const-qualification of the second argument, s2, eliminates the spurious warning in the initial invocation but maintains the valid warning on the final invocation in which a const-qualified object is passed as the first argument (which can change). I was expecting it will throwing error as read only. void consttest_func(const unsigned int consttest_var1){ Although a function may change the values passed in, these changed values are discarded once the function returns. Although the restrict type qualifier did not exist in C90, const did. A constant parameter is declared in the case when it is necessary that the value of the transferred object remains unchanged in the body of the called function. Modified 1 year, 6 months ago. // A function that counts the number of characters specified in an ASCIIZ string, // string s is passed as a constant parameter, // function that counts the number of zero elements of array A, // function that returns a constant number, // a function that returns a constant string. if. When we pass by reference or pointer, we can modify the value referred or pointed, so we can have two versions of a function, one which can modify the referred or pointed value, other which can not. C++ allows functions to be overloaded on the basis of the const-ness of parameters only if the const parameter is a reference or a pointer. When a function is declared as const, it can be called on any type of object, const object as well as non-const objects. int function(const parameters) The parameters will be Let's remember the old C style ugly pointer notations and the const keyword, and how we can ignore constant value inside our custom method. But you know what you will do, when you need constness in C#. Most often this is seen with C-style strings where you have a pointer to a const char. But it is not a problem indeed, since as we saw in the C/C++ example, const& is a contract indeed. void std::vector::push_back(T x)) and then efficiently moving that value in the final place inside the container. When a function name is overloaded with different jobs it is called Function Overloading. All Rights Reserved. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. C pointer to array/array of pointers disambiguation. ADO .NET namespaces, Python. It also seems that missing is an example that shows how the properly-declared standard strcat can be used to do things like strcat(str,".txt") without any compiler diagnostic, while strcat_nc(str,".txt") will give one, since the second parameter is declared as a non-const char*. 1. Parameter passing to a function is extremely important in all programming languages. Changing a copy of a variable will not cause this variable to change in the program.