Let us take a simple example to understand the working of the main function in c language. This will cause the operating system to send a special signal to myprocess called SYSSEGV, which results in unavoidable death. Where function pointers are used in real time? A function may or may not require parameters. The main function serves as the starting point for program execution. The main function in C starts with an opening bracket ( {) and ends with a closing bracket ( } ). Even if a function does not return a value, it has a return type. Explicitly cast implicit type conversions. Write comments that you would want to read five years from now when you've forgotten everything about this code. This example depicts the flow of the main function and various other subsequent function calls in the c language. Your tutorial is very clear to me because i had been taught this very C program while i was in school though its a bonus course for me then. We called testOne(), testFour() from main(), but why were we are able to see the output of testTwo()? Reasons that make it special are -. If I may complete the "usage" function (by using the 'opt' argument) so the message be more informative when encountering an error, I propose this: At the time X86 and Linux were foul words at Sun, but I secretly still did it in my basement. // The calculation function will call add and subtract function inside it. main is the first executed function. The main is a predefined keyword in the C language, so we cannot change its name and meaning. As you write functions, adding them after the main() function and not before, include the function prototypes here. It's much better to catch a NULL pointer in order to emit better error messages and shut down the program gracefully. As you can see in the output window screenshot, that only function testOne(), testTwo() and testFour() executed. This article will look closer at the header file and main function in C programming language. Opensource.com aspires to publish all content under a Creative Commons license but may not be able to do so in all cases. Parameters are read as zero-indexed command-line arguments. void usage(char *progname, int opt); This function takes a second argument, but it is not used in the function's body. Without including the header files, the program will not be executed as the compiler will throw errors. Can you guarantee that doing it in the shell won't add a layer of kernel calls for each write? However a much more elegant approach is to add simply an #include (lt) stdint.h (gt) line in the first section of main.c . Which of the following is an acceptable way for a function to exit in C++: a. int main(int argc, char* argv[]){;} and. Functions in C programming have three general aspects: declaration, defining, and calling. It also makes calling the function slightly faster, since fewer things need to be copied into the function's stack frame. Let us learn about them in detail with syntax and examples. specially in Interviews. No pressure. If the returned value from the main function in C is 000 then the program has executed successfully else, there is some error. read more 2 1 Comments Raga Deepthi Gade Don't worry about it if that doesn't make sense. Main function, as the name suggests, is the most important function in every C or C++ program. In the example above, argv would be a list of the following strings: The argument vector is guaranteed to always have at least one string in the first index, argv[0], which is the full path to the program executed. At the end of this article, you will understand what are Local . he has worked for IBM, Sun Microsystems, Oracle, and most recently Intel doing computersystem performance related work. Some compilers will accept void main, but this is a non-standard extension (it usually means "always return zero to the OS"). The main function in C programming is a special type of function that serves as the entry point of the program where the execution begins. C compilers only recognize "main ()" function for executionnothing else. The void is a keyword that represents function will not return anything but a void value. In this example, I've declared options_t as a struct with four members. A main is a predefined keyword or function in C. It is the first function of every C program that is responsible for starting the execution and termination of the program. It defines starting point of the program. With respect to a python oriented article, I'll put it on the list. :) It failed with errors around the uint32 type on various RedHat flavors (CentOS-5 and Fedora-29). For most C and C++ programs, the true entry point is not main, it's the _start function. The entry function can vary depending on the system, compiler, and standard libraries. C is still C, but knowing the language doesn't mean everyone will use it in the same way. The standard library consists of all general functions. In C , main () is the user-defined function and first calling function in any program. 5. You can run the words together if you want or separate words with an underscore; just make sure they'reall upper case. You can call the function at any point in the entire program. The prototype of main function in C looks like below. However, not all functions return a value. The errno.h header file has all the error handling functions. If a function allows you to call itself within the definition in a C program, it is a recursive function. Load monsters function Main Function Details of the full problem Parse CSV (if you need to see it) trim function for fgets. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators . Whenever I start with a new C-Programm, I will read this again. A possible invocation: ./convert table_in.dat table_out.dat. I also like to gather string constants as #defines in this part of the file. Every C program must contain a main () function. When a known command line option is detected, option-specific behavior happens. 2. by some reasons three is no uint32_t on my Linux system. The details are highly dependent on the operating system and compiler toolchain, so I'm going to pretend I didn't mention it. Here, the int keywords tell that the program will return an integer value and is taking noting as an argument hence used void. Heres an example for calculating and returning the area of a rectangle without taking any argument. Body: The functions body contains all the statements to be processed and executed whenever the function is called. In reply to Thanks for the suggestion Bob by Erik O'Shaughnessy. Less than/greater than ate your post and I replied to nothing, so I think we are both operating at a deficit :) Excellent description of where those typedefs are located, and it serves to illustrate that not all C environments are the same. Main () function is used to call (invoked) the programing code at the run time. Copied/pasted the code to my favorite Linux box and bang compile errors. Some options have an argument, specified in OPTSTR with a trailing colon. Those of you paying attention will now be questioning why opt is declared as a 32-bit int but is expected to take on an 8-bit char? -1. I'm not saying you're wrong to want log files, but I am always interested in writing only as much code as I need to get the job done and no more. To use any library functions, you need to use the header files at the beginning of the program. A very common implementation-defined form of main() has a third argument (in addition to argc and argv), of type char**, pointing at an array of pointers to the execution environment variables. What is main () function? I was using this without noticing it wasn't standard. The opt prefaced variables are used by the getopt() function, and errno is used as an out-of-band communication channel by the standard C library to communicate why a function might have failed. The argument vector, argv, is a tokenized representation of the command line that invoked your program. A function is a set of statements enclosed within curly brackets ({}) that take inputs, do the computation, and provide the resultant output. Syntax of main () function: A main () function declaration can be done in the following ways. It is the console I/O file and contains library functions for console input/output operations. Every C program starts its execution with the main () function. The value returned by the exit function tells the Operating System whether the program is executed successfully or not. Here are the header files available in C. The input/output header file contains all the library functions related to input and output operations. I think, it deserves its own article. main - In C89, the unspecified return type defaults to int . What are main functions in C? 6. As the name gives out, a function call is calling a function to be executed by the compiler. When that changed and X64 and Linux were suddenly OK, I suddenly became the local multi-boot guru and RedHat expert. i have some questions that i might ask later to get clarification. Awesome, thanks! When a function is executed, the expression (a+b) returned by the function sum is assigned to the result variable. A member function will be called using a dot operator (.) He is proficient with Java Programming Language, Big Data, and powerful Big Data Frameworks like Apache Hadoop and Apache Spark. When a C program is executed, the execution control goes directly to the main () function. I insert a comment with a XXX prefix and a short remark describing what needs to be done. These main functions can be compiled and can run on any OS that has a C compiler. Copyright 2022 InterviewBit Technologies Pvt. This page was last modified on 28 September 2022, at 17:58. They make arguments about "continuity of control flow" and other stuff. Functions in C programming are recursive if they can call themselves until the exit condition is satisfied. fprintf(stderr, USAGE_FMT, progname?progname:DEFAULT_PROGNAME); We can use the void keyword as the return type of the main function in c to depict that the function is not returning any value. The ctype.h file includes all character handling functions. EXIT_FAILUREreturns if either test fails and, by setting the external global variable errno to a conventional error code, I signalto the caller a general reason. Note: The function_name and parameters list are together known as the signature of a function in C programming. The difference is that Thank you for this article. The opt variable takes on the character value of any command line options found by getopt(), and the program's response to the detection of the command line option happens in the switch statement. The entry points to freestanding programs (boot loaders, OS kernels, etc) are implementation-defined. What is the main use of function pointer in C? Function prototypes and global variables should be placed in the `*.h` that corresponds to the `*.c` where they are defined. If you have different inputs, you will not write the same code again. The main function can contain call various other functions. C is a whitespace-neutral programming language, so I use whitespace to line up field names in the same column. Red Hat and the Red Hat logo are trademarks of Red Hat, Inc., registered in the United States and other countries. 16 reasons DDEV will be your new favorite web development environment, Supplies FILE, stdin, stdout, stderr, and the fprint() family of functions, Supplies malloc(), calloc(), and realloc(), Defines the external errno variable and all the values it can take on, Supplies memcpy(), memset(), and the strlen() family of functions, Supplies external optarg, opterr, optind, and getopt() function, Typedef shortcuts like uint32_t and uint64_t. It is the first method which gets invoked whenever an application started and it is present in every C# executable file. It doesn't matter what you use, just make sure it's not likely to show up in your codebase in another context, as a function name or variable, for instance. Something went wrong. However, we need to include the library at the beginning of the code for calling a library function. If you have to write comments, do not write about what the code is doing. The #define is a preprocessor directive allows you to specify a name and replacement text. This makes the function signatures simpler, making them easier to remember and not screw up when they're called later. Thanks for sharing your knowledge. 2. main function is called by operating system. In simple terms, we can say that the main function in C is the entry point of any C program. The main function in C is the first function to be executed by the Operating System. A main function is followed by opening and closing the parenthesis brackets. The platform offers free courses for numerous programming languages, including C. You can sign up and select the course you want to take and get acquainted with the basics of that programming language. A function is a set of statements enclosed within curly brackets ( {}) that take inputs, do the computation, and provide the resultant output. It has a) argument count and b) argument vector (string argument) Upon completing the course, you will be confident enough with your skills to land a high-paying job in any multinational company. Void main () is the entry point for execution in C program. The main() function is the first function in your program that is executed when it begins executing, but it's not the first function executed. // calling the calculation function from main function. - Michael Burr Jun 5, 2009 at 19:21 1 I see. However, we can avoid the use of extra pointer by using inline functions. The argv[] array contains all the arguments in the form of an array. 1. Since you mention that you also code in Python, is it too much to ask for essentially the same template using Python's standard libraries? (View:-26) Choose the correct answer from below list OK, that's a lot. It is a special function that always starts executing code from the 'main' having 'int' or 'void' as return data type. Every C program coded to run in a hosted execution environment contains the definition (not the prototype) of a function called main, which is the designated start of the program. This content is accurate and true to the best of the authors knowledge and is not meant to substitute for formal and individualized advice from a qualified professional. You can create two functions to solve this problem: createCircle () function The first function is _start(), which is typically provided by the C runtime library, linked in automatically when your program is compiled. User defined functions are written in 3 steps in C language. It's a nice article to how to write a good C-Program and i learnt a few new things related to C programming. The main function in C is a user-defined function and hence we can also pass parameters to the main function. Hi rajkishor, this is a best example to understand importance of main() functioni am come out from lots of problems from when i started to read your examples i will recommended to all my friend.good job.. keep it up to share your knowledge.. thx a lot Yea it's really super.Even if it's a basic question i don't know before this now i can easily understood . We will discuss about it later, // Calling the function to find the greater number among the two. Today's programming environments are much more fluid and you have to decide how much you want to "forage" from the environment and how much you are willing to re-implement to avoid the problems like the one you encountered. A function is a block of code that performs a specific task. In fact, not just this article, every C program that you see will have a main function. thanks for visiting, take care. Learn. Heres an example of such a function. The Arena Media Brands, LLC and respective content providers to this website may receive compensation for some links to products and services on this website. It can return either int or void data type. Another thing I won't talk about adding to your program is comments. It shall have one of the following forms: The names of argc and argv are arbitrary, as well as the representation of the types of the parameters: int main(int ac, char** av) is equally valid. It is prohibited to write void main () by the C++ standard which when written result in this compitation error: These library functions or inbuilt functions help programmers to perform common programming task rapidly and efficiently. We need functions in C programming and even in other programming languages due to the numerous advantages they provide to the developer. In reply to i guess you should ditch sys by David Ramunno (not verified). User-defined functions are the functions that are defined by the user at the time of writing the program. If you declare main as int you should also return an int. It is a mandatory function to compile and run c programs. The editors reports an error about using the header file iostream.h, while I was taught by my tutor (via video lectures) to include this header file for writing some initial programs to do some analyzing / calculations etc. It failed with errors around the uint32 type on various RedHat flavors (CentOS-5 and Fedora-29). Stay tuned! We put the return 0; statement as the last statement to mark the ending of the main function in C and to check if the program has been executed successfully or not. We give the system access to our C++ code through the main () function. The main () function or complete C program is treated as a normal procedure/ process. 3. The usage() function validates the progname argument using a conditional assignment in the fprintf() call. Post Graduate Program in Full Stack Web Development. If you change or refactor the code, you need to update or expand the comments. Void Functions in C By Dinesh Thakur Functions may be return type functions and non-return type functions. When an option has an argument, the next string in argv is available to the program via the externally defined variable optarg. return_type: Here, we declare the data type of the value returned by functions. There are two types of main function:- (i) Main function without parameters (ii) Main function with parameters The main function is given an option to have or not have parameters to allow input from the command line. Given below is an example of such a function. You are responsible for ensuring that you have the necessary permission to reuse any work on this site. myFunction () is the name of the function void means that the function does not have a return value. It is a very first function of any c program that, starts executing and terminating (ending) the program. The void main(void) function neither takes an argument nor returns a value. or ask your own question. One little note regarding the code: I am happy that my articles are helping you in your study. int main() { .. return 0;. A C program starts with a main() function, usually kept in a file named main.c. This shows how the return value . arg1, arg2, argn: It is the argument or parameter list that contains all the parameters to be passed into the function. 2.1 Portable main functions in C. The portable main functions in C are supported by all operating systems. Provides diagnostic testing obtaining optimal patient effort and results. These comments are closed, however you can, #define USAGE_FMT "%s [-v] [-f hexflag] [-i inputfile] [-o outputfile] [-h]", #define ERR_FOPEN_INPUT "fopen(input, r)", #define ERR_FOPEN_OUTPUT "fopen(output, w)", #define ERR_DO_THE_NEEDFUL "do_the_needful blew up". The genenal "policy" of this linked list is to maintain the list in sorted coder. And, one little note about a formatting of the usage() output. What is a Translator Types of Applications Platform Dependency in C Introduction to C Programming Language History of C Programming Language Library and IDE in C Language Structure of C Program Environment Setup for C Program Codeblocks IDE Setup in Windows for C Program Development Creating a new project using CodeBlocks IDE C - Fundamentals So for runnin. But if there is no return value, then the void is the return type of the function. The user defined function has a void return type. // The main function. void usage(char *progname, int opt) { Syntax of main function. A function in C++ refers to a group of statements that takes input, processes it, and returns an output. The arguments array has a size of (argc + 1) and contains a null value at the end. These functions may or may not have any argument to act upon. A program shall contain a global function named main, which is the designated start of the program in hosted environment. The main function may contain any number of statements. Modified today. The Methods are identified by their name. Functions are made for code re-usability and for saving time and space. Note: Note: We can write a program without the main function, but it is a frowned-upon practice. The main function can in-turn call other functions. Viewed 6 times. int main(int argc, const char* argv[]){;} is. We can simply call them without defining them as they are already defined. Refer to the image below to see the basic prototype of the main function. We can create two functions to solve this problem: a function to draw the circle a function to color the circle Dividing a complex problem into smaller chunks makes our program easy to understand and reusable. Paym. But if you have to use a global variable, declare them here and be sure to give them a default value. Global variables are a bad idea and you should never use them. I'm aware of the difference between a char*[] and const char*[] but I wonder why one would like to use the latter.. Are there use cases where one would want to change command line arguments? Every C program have a main () function. exit(EXIT_FAILURE); These functions are usually used for small computations. Assists with the development and review/revision of all PFT Lab Policies and Procedures. Thanks for sharing your experience; fixing heisenbugs can be notoriously difficult to accomplish. In reply to Can you guarantee that doing by Bob McConnell (not verified). These are the functions that a developer or the user declares, defines, and calls in a program. Are you objecting to returning EXIT_SUCCESS or EXIT_FAILURE instead of zero or one? Some people complain about having multiple return statements in a function body. What are main functions in C? visual-c++. The main function: Can't be declared as inline. Printf(), scanf(), ceil(), and floor() are examples of library functions. If a return value is provided, the return type is the data type of the value. We evaluated the impact of CKD and lung function decline in a large-scale longitudinal study. main () is a special function in C programming language. Timing is everything. That's where I'll leave myself a little breadcrumb. In reply to This is excellent! A function can return a value without accepting any arguments. It controls all other child functions. This example declares an options variable initialized with default values and parse the command line, updating options as necessary. The list defines the data type, sequence, and the number of parameters to be passed to the function. Here is a simple program to show what I just said: Simple Main () Example But don't be so quick to dismiss Cit's a capable and concise language that has a lot to offer. I wish I had seen an example like this several years ago. It is the math header file and contains all library functions related to math operations. The Main Function In C, the "main" function is treated the same as every function, it has a return type (and in some cases accepts inputs via parameters). The main function is the programs entry point, as that is where the compiler will start executing the code. When I was writing C regularly, it was nearly always in support of a particular software/hardware combination that was reasonably "static" and only changed for major/minor OS updates or forklift hardware upgrades. As a matter of course, I always include a usage() function that main() calls when it doesn't understand something you passed in from the command line. In simple words, programs of C and C++ must have main function, because program execution starts from main() function. As we have seen above, the int keyword depicts that the function is returning an integer value. If your user defined function call is not included in "main ()" function, then it will never be executed during program execution. main () function can be also regarded as the captain of the ship. The opinions expressed on this website are those of each author, not of the author's employer or of Red Hat. So, main() function is mandatory for any C program. you try..God bless you. Raj is an ardent coder who loves exploring new technology. Find important definitions, questions, meanings, examples, exercises and tests below for What is main() in c language, is it a input or output statement?. I had intended to emit the offending option in the fprintf but must have forgotten it in the fugue of writing. This program compiles but doesn't do anything. 1. the full listing of a program has lost its #include Now let me explain a simple code snippet. In such cases, the keyword void indicates to the compiler that the function will not return any value. This header file consists of all the variable argument functions. Thanks for the VERY quick answer. What Are the Main Types of Functions in C Programming? Note: In case when return statement is used in the main function in C, the return value is passed as the argument to the implicit call to the exit() function. Back to: C Tutorials For Beginners and Professionals Local vs Global Variables in C Language with Examples. Functions in C are the basic building blocks of a C program. - Returns int value to the environment which called the program. The standard C library does lots of things; explore header files in /usr/include to find out what it can do for you. The string tells cppto look for a file called header.h in the system-defined header path, usually /usr/include. Consult the getopt(3) man page to learn how OPTSTR will affect getopt()'s behavior. It is the designated entry point to a program that is executed in a hosted environment (that is, with an operating system). The course will help you master the primary and the advanced concepts of numerous programming languages and applied learning on the most popular tools. /* NOTREACHED */ Heres an example with all the three general aspects of a function. In the main function, we read two integers from the console input and pass it to the sum function. In reply to If you declare main as int by oxagast (not verified). Hence, it is essential to learn how to create and use functions to optimize your program. The main function is called at program startup after initialization of the non-local objects with static storage duration. I haven't tried anything because I do not know how to even start this. Hence, the factorial of 8 is 8*7*6*5*4*3*2*1 = 40320. The rules for giving function names are the same as the rules for giving the variable names. While using functions in C programming, the pointer for execution flow jumps to the function definition after the function call. The manner in which the arguments given at the OS command line are converted into the multibyte character arrays referenced by argv may involve implementation-defined processing: Demonstrates how to inform a program about where to find its input and where to write its results. The following program demonstrates a function in C programming that takes arguments and returns a value. But now you have a solid skeleton to build your own command line parsing C programs. printf("The area of the Rectangle is: %d\n",area); printf("Enter the length of the rectangle: "); printf("Enter the width of the rectangle: "); C functions may accept arguments but not provide any return value. 2022 The Arena Media Brands, LLC and respective content providers on this website. In the code mentioned above, we have created two separate functions- the func_A and the func_B. After external declarations, I like to declare typedefs for structures, unions, and enumerations. OK, this program still does almost nothing when you compile and run it. The Operating System hands over the control to the main function for the execution of other functions. Take care, happy learning :). I can offer $15/hr. In reply to If the Main function in C by Ghanendra Yadav. A int keyword is used to reference an integer data type. Ok, I'm not even going to try to lie. There can be two types of main function prototypes. These library functions are generally preferred to obtain the predefined output. However a more elegant approach is to add simply an "#include, My comment was supposed to be instructive and helpful for RedHat users. C# applications have an entry point called Main Method. Every program in C has a function. Several restrictions apply to the main function that don't apply to any other C functions. Hence, the parameter list is optional. I need someone with more experience in C to help fix the flaws in this code. The ptr consists of this address of func_B when we call the func_A. It should have a return type, int, to check for failure or success. Another good topic would be debugging, a few examples how you debug code than a program was coredumped and killed with different signals. Here, Function Name: It is mandatory and it defines the name of the method or function.The method signature consists of the method name and parameter list. The main function will send two numbers to the addition function. on a object where it will manipulate data related to that object only as follows Box myBox; // Create an object myBox.getVolume (); // Call member function for the object #define OPTSTR ":vi:o:f:h" Finally, I write functions that aren't boilerplate. This header file consists of all the time-related functions. How do I come about this situation and execute / run my programs without errors? Seriously, don't use global variables. In the case of an int return type, if the returned value from the main function in C is. So, #defines which are created in one source file are NOT available in a . (work done from home at your convenience). A main () function is followed by opening and closing parenthesis brackets. c++11. is it possible the C file having main ( ) function to be the header file of another C file having main ( ) function.could you explain. printf("Enter the two numbers to add:"); // Accepting arguments with void return type. Function definition must return only one value at the end of the execution. If you have to put copyright or licensing text in your source, put it there. Learn how to structure a C file and write a C main function that handles command line arguments like a champ. This means that we do not have to write a definition or the functions body to call them. The first is without any argument and the second one is with the arguments. If you call a function before the declaration, the C compiler will by default consider the return type to be int and show an error if the data type of the return value is anything except int. Thanks for the suggestion Bob, however I have to wonder how redirecting stderr to a file in a shell doesn't accomplish the same thing without code maintenance overhead? This is the minimum set of global includes that I'll include by default for the following stuff: This doesn't make a lot of sense right now, but the OPTSTR define is where I will state what command line switches the program will recommend. The valid C/C++ main signatures are: int main() int main(int argc, char* argv[]) int main(int argc, char** argv) In C/C++ language, the main () function can be left without return value. :-). raj bahi these tutorial helping me a lot so thanks, i can very easily understand the importance of main() from your example thanks, I looked at your discussions re What is header file and main function in c and c++ program. It is an entry point or starting point of program execution. The first function is _start (), which is typically provided by the C runtime library, linked in automatically when your program is compiled. You also touched slightly "errno is used as an out-of-band communication channel by the standard C library to communicate why a function might have failed". A function can also be referred as a method or a sub-routine or a procedure, etc. In reply to You mentioned somewhere by WWWillem (not verified), i guess you should ditch sys/types.h in favour of stdint.h which was implemented in c99 to standartise these accross systems. Information about What is main() in c language, is it a input or output statement? We need to use the keyword inline before a function to make it an inline function. It is uniq as it represents a distilled experience. The signal.h file contains all the signal handling functions. Keep visiting and please try to spread this to your friends. I considered briefly not using uint32_t (or a cognate) in my code, but this article was originally titled "How To Write a C Main Function Like Me" so I wrote it the way I would normally write it. You can call a function multiple times, thereby allowing reusability and modularity in C programming. Here are a few other ideas You mentioned _start() function, tell us more! The function declaration lets the compiler know the name, number of parameters, data types of parameters, and return type of a function. RAJKISHOR SAHU (author) from Bangalore, Karnataka, INDIA on March 17, 2011: @speedbird: i write these for beginners only, if it helps others then its my luck. In this article, you have learned everything about functions in C programming. This function initializes the program runtime and invokes the program's main function. Initially, the Operating System gives control to the main function in C. The main function in C is called by the Operating System itself at the run time, not at the compile time. I think this is a very simple and powerful example of importance of main function in any C or C++ program. The non-return type functions do not return any value to the calling function; the type of such functions is void. These functions are known as user-defined functions. The Main method can be declared with or without a string [] parameter that contains command-line arguments. The first things I add to a main.c file are includes to make a multitude of standard C library functions and variables available to my program. On the other hand, the argv[] is the pointer to the first element of the arguments array. Lets understand what these aspects mean. There are a couple of points for style here: The command line signature for this program, if it were compiled, would look something like this: In fact, that's what usage() will emit to stderr once compiled. Main function returns an integer value indicating a success (with a value of zero) or a failure (a negative number). Over time, the code mutates away from anything resembling what the comments describe. The strings are modifiable, although these modifications do not propagate back to the execution environment: they can be used, for example, with std::strtok. Function Pointer are pointers i.e. speedbird from Nairobi, Kenya on March 13, 2011: I did C and C++ some time back but with the advent of Visual Basic I almost forgot about C and C++. The main () function is the first function in your program that is executed when it begins executing, but it's not the first function executed. The size of the array pointed to by argv is at least argc + 1, and the last element, argv[argc], is guaranteed to be a null pointer. Thank you for the praise and you are of course correct with respect to the opt argument being unused in the body of the function. }. 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