{"id":68,"date":"2018-07-09T12:14:56","date_gmt":"2018-07-09T12:14:56","guid":{"rendered":"http:\/\/itp1.epgpbooks.inflibnet.ac.in\/?post_type=chapter&p=68"},"modified":"2019-05-14T11:44:26","modified_gmt":"2019-05-14T11:44:26","slug":"functions-in-c-i","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/itp1\/chapter\/functions-in-c-i\/","title":{"rendered":"Functions in C++ I"},"content":{"raw":"
\"epgp<\/a>\r\n<\/span><\/div>\r\n\r\n
\r\n\r\nFunctions<\/strong>\r\n\r\n \r\n

Functions in C++, offer similar solution for organizing large and complex program. While writing a program, the main program becomes too large and complex if programmer writes all the steps within it. The readability of program also turns to be complex. Testing or debugging becomes quite difficult. Instead, if he collects certain steps, for example finding square root or displaying record on the screen, bundles them in a routine and writes them in either a separate file or same file outside the main() function, the main programme would look much simpler. Functions facilitates partitioning a complex problem into set of sub-problems which are easily understandable, maintainable and manageable. Once the problem is divided into set of tasks, we can write function for each task. Each function implements a small task or particular aspect of a large program. A complete application can then be developed integrating all such functions.<\/p>\r\n \r\n\r\nFunction can be defined as a group of statements that is given a unique and meaningful name within a program. It is created to perform a specific task.<\/strong>\r\n\r\n \r\n\r\nEvery C++ program has at least one function, which is main().One can define more functions as per the need.\r\n\r\n \r\n\r\nFunctions in C++ are very similar to functions in C except the return type default. The default return type in C is int whereas default return type in C++ is void. There are three steps to create and use a\r\n\r\n \r\n\r\nfunction in C++ program.\r\n\r\n \r\n\r\n1.\u00a0\u00a0\u00a0\u00a0\u00a0 Declaring a function\r\n\r\n2.\u00a0\u00a0\u00a0\u00a0\u00a0 Defining a function\r\n\r\n3.\u00a0\u00a0\u00a0\u00a0\u00a0 Calling a function\r\n\r\n \r\n

Let us understand generalized structure of declaring, defining and calling a function along with an example. Assume that function to calculate x<\/strong>y<\/strong> is intended, where x and y would be given by a user. Function would be given two values as input, x and y and it would return x<\/strong>y<\/strong> as a result.<\/p>\r\n \r\n\r\nDeclaring a function<\/strong>\r\n\r\n \r\n

Declaration of a function includes stating to a compiler that the declared function is defined in the program, or its object module will be made available at the time of linking . Declaring a function is also known as function prototyping. In C++, function prototyping is mandatory. Compiler error would be raised if a function is called without its prototype mentioned in the program before calling of the function. If a programmer writes a function to add two integers, It can be named as add and prototype of which can be written as int add(<\/span>int , int). This prototype specifies that add is a function which takes two integers as input and returns an integer value, which in this case will be <\/span>sum of the given numbers. A function prototype is useful while checking whether the function when called is called with <\/span>correct set of arguments. And the knowledge of return type will help <\/span>compliler determine, that the call to the function is placed at correct place or not.<\/span><\/p>\r\n\r\n<\/div>\r\n

\r\n\r\n \r\n\r\nDefining a Function<\/strong>\r\n\r\n \r\n\r\nDefining function means implementing the function. The basic syntax for defining any function in C++ is: returnDataType functionName(dataType argument 1, dataType argument 2\u2026\u2026\u2026 dataType argument\u00a0 n)\r\n\r\n{\r\n\r\nfunction statements;\r\n\r\n}\r\n