Computer Science
Write Functions in C
Writing functions in C involves creating reusable blocks of code that can be called from other parts of a program. Functions can take input parameters and return output values, and can be used to perform specific tasks or calculations. Properly written functions can improve code readability, organization, and maintainability.
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eBook - ePubLearn C Programming from Scratch
A step-by-step methodology with problem solving approach (English Edition)
- Mohammad Saleem Mir(Author)
- 2024(Publication Date)
- BPB Publications(Publisher)
Inline functions: Rather than being called a distinct function, inline functions are functions extended inline by the compiler at the call site. By lowering the cost of function calls, inline functions are meant to increase performance. The inline keyword is often used to define inline functions. However, the compiler finally decides whether to inline a function.- Function pointers: In C programming language, functions can be provided as arguments, handled as variables, or saved as variables. Function pointers are variables that hold a function’s memory address, and they let you use the function pointer to invoke a function indirectly. Implementing callback functions and developing adaptable and extendable code structures benefit from using function pointers.
- Recursive functions: Recursive functions either directly or indirectly call themselves by segmenting larger issues into smaller subproblems and resolving each subproblem using the same function; they can solve problems. Recursive functions feature one or more recursive calls that address more specific examples of the issue and a base case that ends the recursion. Examples of recursive functions include calculating factorial, Fibonacci sequence, and traversing tree structures. Based on the function definition, we have two kinds of functions:
For example: void add () { // statements } Defining a function The general form of a function definition in C programming language is as follows: return_type function_name (parameters) { body of the function }- Inbuilt functions : The functions that are part of the C standard library, meaning that these functions are already defined and can mean that they code for them. The C standard library provides numerous built-ins that your program can call. For example, strcat () to concatenate two strings, memcpy () to copy one memory location to another location, and many more functions.
- User-defined functions: The functions not part of the C standard library whose code is written by a user. C allows us to define functions according to our requirements. These functions are known as user-defined functions.
A function definition in C programming consists of a function header and body .Parts of a function:- Return type : A function may return a value. The return_type is the data type of the value the function returns. Some functions perform the desired operations without returning a value; in this case, the return_type
eBook - ePubLearn Programming with C
An Easy Step-by-Step Self-Practice Book for Learning C
- Sazzad M.S. Imran, Md Atiqur Rahman Ahad(Authors)
- 2024(Publication Date)
- Chapman and Hall/CRC(Publisher)
CHAPTER 4 FunctionsDOI: 10.1201/9781003302629-4A FUNCTION IS A SET of statements that performs a specific task. Every C program must have at least one main() function, but any additional functions can be defined and used. This chapter presents and discusses two types of functions: library and user-defined.4.1 FUNCTION TYPES
When we need to execute a block of statements several times, we define a function that contains those statements and call it every time we need it. Functions are used to make the codes more readable and reusable. In C, there are two different types of functions.- Library functions: The standard library functions are predefined in the library (.lib) and declared in several header files (.h). We can call these functions anytime we need to do the task that that function defines. printf(), scanf(), gets(), puts(), etc., are some examples. Because functions printf() and scanf() are declared in the stdio.h header file, the header file must be included before they can be called in a C program using the preprocessor directive #include. Example is #include stdio.h>
- User-defined functions: These functions are defined by the programmer and afterward reused as needed.
4.2 FUNCTION STRUCTURE
Syntax of the C functions: return_type function_name(argument_list){ //blocks of valid C statements } return_type can be any valid data type like int, char, long int, float, double, etc. It can also be void if the function returns nothing. Except for any keywords, function name can be any single alphanumeric word, preferably meaningful.argument_list is a list of variables and their data types that are passed to the function as input. The formal parameter refers to the parameters that appear in the function declaration, whereas the actual parameter refers to the parameters that appear in the function call.For example, the following function takes two floating numbers, a and b, as its arguments and returns the total a+b. Here, a and b are the formal parameters, whereas x and y are the real parameters in the addition(x, y) function call.
eBook - ePub- Yuan Dong, Fang Yang, Li Zheng(Authors)
- 2019(Publication Date)
- De Gruyter(Publisher)
3FunctionsC++ inherits all the C syntax, including the definition and usage of functions. In process-oriented programming (also known as structured programming), function is the basic unit of module division, and an abstract of the problem-solving process. Function is also important in object-oriented programming, in which it is an abstract of functionalities.To develop or debug a complex system, engineers will usually divide it into several subsystems, and then develop or debug based on these subsystems. Subprograms in high-level program languages are used to realize this kind of module division. In C and C++, subprograms are embodied as functions. We usually abstract functions from independent and frequently used functionality modules. Once a function is written, we can reuse it only knowing its functions and usage, without needing to know its specific implementation. In this way code is reused, development efficiency and program reliability are improved, and collaboration, modification, and maintenance can be realized more easily.3.1Definition and Use of Function
A C++ program consists of one main function and several subfunctions. A program is executed starting from its main function. The main function may call subfunctions, and subfunctions may in turn call other subfunctions.The function that calls other functions is named a “calling function ”, and the function called by others is named a “called function ”. A function may call another function and also be called by another. Thus it can be a calling function in one occasion and a called function in another.3.1.1Definition of Function
1.Syntax form of function definition
2.Type of function and return value
The type identifier defines the type of the function, and also the type of the return value of the function. The return value of the function is the result that the function returns to its calling function, which is given by a return statement, such as “return 0
eBook - ePubC Programming
Learn to Code
- Sisir Kumar Jena(Author)
- 2021(Publication Date)
- Chapman and Hall/CRC(Publisher)
A function can be defined as a group of statements enclosed within a block with a valid identifier and can perform a specific task. Generally, a function will process information that is passed to it from the calling portion of the program and return a single value. Information is passed to the function via special identifiers called arguments (also called parameters) and returned via the return statement. A user-defined function only executes when it is called.A function can be defined as a group of statements enclosed within a block with a valid identifier and can perform a specific task.The general syntax of a user-defined function is shown in Figure 9.5 .So, to begin our discussion, let us write a simple function using the above syntax. In this function, we include a single statement body. The work of this function is to print a line of a statement.Figure 9.5 Syntax of user-defined function.- In the above function, it is clearly mentioned that the function does not return anything, so the return type is void;
- This function also does not take any parameters, so the parameter list is empty;
- The name of the function is printLine, and when this function is called, it executes a single line present in the body of the function.
As discussed earlier, a user-defined function cannot be executed of its own. It should be called by the main() function whenever it is needed.Program 9.1
1. #include<stdio.h> 2. void printLine() 3. { 4. printf("\n C Programming Learn to Code"); 5. } 6. void main() 7. { 8. printLine(); 9. printLine(); 10.printLine(); 11. }Output:C Programming Learn to Code C Programming Learn to Code C Programming Learn to CodeExplanation:The printLine() function is called three times, so it prints “C Programming Learn to Code” three times. We can solve the above problem by writing three printf() statements inside the function main() as shown in Program 9.2 , and we get the same output as from Program 9.1 .Program 9.2
1. #include<stdio.h> 2. void main() 3. {
eBook - ePub- R. Becker(Author)
- 2018(Publication Date)
- Chapman and Hall/CRC(Publisher)
6 Writing FunctionsFunctions are the heart of S and writing or modifying them is the most important part of creating new capabilities based on S. This chapter discusses how to write functions. section 2.7 introduced this topic; if you want a brief discussion of the important features, you should read that section first. This chapter picks up where section 2.7 left off, presenting new examples as well as a more complete description of functions, describing parts of the S language (such as looping expressions) that are used in writing functions, discussing the interface between S and commands in the UNIX operating system, and showing how functions can be edited and debugged.6.1 Overview of Functions First we give a description of the syntax of function definitions together with examples of functions. The section closes with a brief description of how to design functions.A function in S can have any number of arguments, and the computation that is done by it can be anything expressible in S. The general syntax of a function definition is6.1.1 The General Form of Functionsfunction( arguments )expressionwhereargumentsgives the arguments separated by commas, andexpression(referred to as the body of the function definition) is any legal S expression. For functions that do nontrivial calculations, the body is usually a sequence of expressions enclosed in braces and separated by semi-colons or newlines. The value of the last expression between the braces becomes the value of the whole expression, and therefore the value returned by the function. For example, here is a function, larger , that takes two arguments, x and y , and returns an object whose elements are the larger of the corresponding elements of the arguments:larger ← function(x, y){ y.is.bigger ← y > x x[y.is.bigger] ← y[y.is.bigger] x }The body of the function is a braced list of three expressions. The third expression will be returned as the value of the function.
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