Input means to provide the program with some data to be used in the program and Output means to display data on screen or write the data to a printer or a file.
C programming language provides many built-in functions to read any given input and to display data on screen when there is a need to output the result. In this tutorial, we will learn about such functions, which can be used in our program to take input from user and to output the result on screen. All these built-in functions are present in C header files, we will also specify the name of header files in which a particular function is defined while discussing about it.
The standard input-output header file, named stdio. When you will compile the above code, it will ask you to enter a value. When you will enter the value, it will display the value you have entered on screen. It is known as format string and this informs the scanf function, what type of input to expect and in printf it is used to give a heads up to the compiler, what type of output to expect.
Same is the case for output. In C Language, computer monitor, printer etc output devices are treated as files and the same process is followed to write output to these devices as would have been followed to write the output to a file. NOTE : printf function returns the number of characters printed by it, and scanf returns the number of characters read by it.
In this program printf "studytonight" ; will return 12 as result, which will be stored in the variable ibecause studytonight has 12 characters. The getchar function reads a character from the terminal and returns it as an integer. This function reads only single character at a time. You can use this method in a loop in case you want to read more than one character.
The putchar function displays the character passed to it on the screen and returns the same character. This function too displays only a single character at a time. In case you want to display more than one characters, use putchar method in a loop. When you will enter the value, it will display the value you have entered. The gets function reads a line from stdin standard input into the buffer pointed to by str pointeruntil either a terminating newline or EOF end of file occurs.
The puts function writes the string str and a trailing newline to stdout. Ignore if you are not able to understand this now. When you will compile the above code, it will ask you to enter a string. When you will enter the string, it will display the value you have entered. The main difference between these two functions is that scanf stops reading characters when it encounters a space, but gets reads space as character too.Designing The Input Function using getchar()
If you enter name as Study Tonight using scanf it will only read and store Study and will leave the part after space. But gets function will read it completely. Made with by Abhishek Ahlawat. Ruby Servlet JSP.
Operating System. Computer Architecture.Returns the character read. For getcharuse ferror or feof to check for an error or for end of file. Each routine reads a single character from stdin and increments the associated file pointer to point to the next character.
These functions lock the calling thread and are therefore thread-safe. By default, this function's global state is scoped to the application. To change this, see Global state in the CRT. The standard stream handles that are associated with the console, stdinstdoutand stderrmust be redirected before C run-time functions can use them in UWP apps. For additional compatibility information, see Compatibility. You may also leave feedback directly on GitHub.
Skip to main content. Exit focus mode. Remarks Each routine reads a single character from stdin and increments the associated file pointer to point to the next character.
The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. The code inputs results from first getchar ; and then exits without waiting for more input. Why is that? Use a while loop after each getchar if you want to process only one character. First, getchar returns an intnot a char. This is so it can return any valid character as a value Second, when users type an answer, the information contains the character Y or N, you hope plus a newline.
There could be leading blanks; there could be trailing garbage. So, your F probably gets the first character; the C reads the newline, not waiting for more input.
If you want to read lines and process each in turn, use fgets to read the line and sscanf to parse the result. Note that newlines go at the end of outputs, in general. You could omit them from the prompt messages so that the input appears on the same line as the prompt in an interactive session. The calling code does not really handle EOF properly — where the uses triggers an EOF condition by typing Control-D for example before entering any data.
It's because when you press Enter, after answering the first question, the enter key gets stored in the next variable C. To correct it just write another getchar to eat up the extra Enter. When you enter a character ,it is stored in F,then when you press enter,it is stored in stdin buffer and when next getchar comes it reads it's input from the stdin buffer ,for this use fflush stdin before every getchar you use. Learn more.
Cannot figure out how to use getchar ; in C Ask Question. Asked 6 years, 6 months ago. Active 1 year, 11 months ago. Viewed 45k times.
Jonathan Leffler k gold badges silver badges bronze badges. Read its documentation man getchar or equivalent to see why. Welcome to Stack Overflow!
Unlike some other Internet forums you may know, Stack Overflow is not a discussion site, nor is it homework help site. It is a question -and- answer site. Users such as yourself ask questions and other users attempt to answer them. What is your question? Active Oldest Votes. Use a while loop after each getchar if you want to process only one character printf "Do you have a Fever?
And what if the user enters a blank line? Note that you'll want to put the while loops after you use F and C or they'll be reassigned to the other chars they eat up in the loops. I know that's obvious to you experts out there but adding the clarification for n00bs like me. Use a variable other than C or F in the while loops. And, preferably, factor the loops out into a function. Jonathan Leffler Jonathan Leffler k gold badges silver badges bronze badges.
Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. The getchar function will return each character, one at a time, until the input buffer is clear.
So your loop will continue to cycle until getchar has eaten any remaining characters from the stdin stream buffer. Some implementations ie. Because in some implementations of getchar when you press the key 'x' and ENTER, there are two caracters in the buffer the 'x' and a newline char. I know, this is a little dumb You should skip newlines in your loop.
Learn more. Using getchar in a while loop Ask Question. Asked 10 years ago. Active 2 years, 8 months ago. Viewed 19k times. Active Oldest Votes. It's subjective Judging from the man page "reads the next character from stream" we would expect that each key is read as soon as it pressed; actually the stdin is buffered by lines. This should work Also, your code still has the same behaviour as the OP's.
Mar 31 '10 at Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. The Overflow How many jobs can be done at home? Featured on Meta. Community and Moderator guidelines for escalating issues via new response….Recent Posts. You do not need to specify the size of array when declaration is made in the above fashion. The null character gets implicitly added into the string.
Note that here we have to include space and null character as separate characters as they are too part of string. This is the classic array declaration method that we have used above for strings. However, always remember that the you will be able to store size-1 characters as the last character will be null.
Since char data type occupies 1 byte in memory hence the address space increments by 1 byte. As seennull character will always be the termination of the string.
Usually used with file stream. However, standard input stream is also acceptable. Notice that in order to print the output we had to support it using puts. Thus, sprintf is used to store formatted data as a string and should be avoided in code. There are a variety of string operations that can be performed. We shall go through each one of them in the future section.
When you try to compile the code, it will compile however the compiler will throw a warning message as follows:. Thus, it warns us that gets is a deprecated and dangerous function and should be hence avoided. Strings in C — getsfgetsgetlinegetcharputsputcharstrlen Written By - Pooja. Reading Strings: There are multiple methods using which a string can be read which has been entered by user. The main drawback of scanf to use to input string; is that the function terminates as soon as it finds a blank space.
Also note that, for scanning strings, you do not need the ampersand character precede the string name str.
Null character gets automatically appended on encountering a blank space to mark the end of string. Using gets function in C : Should no longer be used : Using getsstring can be read as follows: gets str ; gets overcomes the shortcomings of scanf. Gets stands for get string. The function takes starting address of the string which will hold the input and automatically appends the null character at the end of the string. Since it is sometimes used in older code which is why the GNU C Library still provides itwe need to understand how it is used.
The gets function takes one parameter, the string in which to store the data which is read. It reads characters from standard input up to the next newline character that is, when the user presses Enter buttondiscards the newline character, and copies the rest of the data into the string. If there was no error, it returns the same string ; otherwise, if there was an error, it returns a null pointer.
getch() function in C with Examples
We shall see going ahead our first string operation example using gets. Rather than reading a string from standard input, fgets reads it from a specified stream, usually file stream up to and including a newline character. It stores the string in the string variable passed to it, adding a null character to terminate the string. The number of characters that fgets reads is one less than than number specified; it stores the null character in the last character space.
You must supply at least as many characters of space in the string, or your program might crash, but at least the fgets function protects against overflowing the string and creating a security hazard. If there is no error, fgets returns the string read as a return value else for example if the stream is already at end of file, it returns a null pointer.A macro call is similar to a function call.
Thus, it consists of a macro name followed by a comma-separated argument list enclosed in a pair of parentheses. If a macro does not require any arguments, the pair of parentheses must still be used. The getchar macro is used to read a single character from the standard input stream, i. A call to get char takes the following form: getchar.
This macro waits until a key is pressed and then returns its value after converting to integer. The value returned can be assigned to a variable of type char. However, note that this macro actually reads the data from the input buffer which is processed by program only when the Enter key is pressed.
Thus, getchar does not return a value until the user presses the Enter key. As a result, it is not suitable for interactive programs. We can instead use the getch and getche functions which directly read the data from the keyboard. The putchar macro is used to write a single character on the standard output stream i. A call to this macro takes the following form: putchar cwhere c is an integer expression representing the character being written.
Although this macro expects an argument of type int, we usually pass a character to it. The argument value c is converted to unsigned char and written to the standard output stream. The getch and getche Functions The getchar macro is not suitable in interactive environments due to the use of line buffering. The C standard library does not provide any facility that is guaranteed to provide an interactive character input. Hence, most C compilers provide alternative functions for use in such interactive environments.
Like the getchar function, calls to these functions take the following forms: getch and getche. The getch and getche functions wait for a key press and immediately return its value. The only difference between these functions is that the getche function echos i. Even '. Since reading is done character by character, this provides an opportunity to access an individual character.
So, character counting is possible. Dinesh authors the hugely popular Computer Notes blog. Where he writes how-to guides around Computer fundamentalcomputer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us. C Programming Theory. Basic Of C Prog.
About Dinesh Thakur. Related Articles. History of C? Comments in C. Basic Courses. Advance Courses.The character to be printed is fed into the function as an argument, and if the writing is successful, the argument character is returned.
Otherwise, end-of-file is returned. The following program uses getchar to read characters into an array and print them out using the putchar function after an end-of-file character is found. The program specifies the reading length's maximum value at characters. It will stop reading either after reading characters or after reading in an end-of-file indicator, whichever comes first.
From Wikibooks, open books for an open world. The putchar function is specified in the C standard library header file stdio. Sample usage [ edit ] The following program uses getchar to read characters into an array and print them out using the putchar function after an end-of-file character is found.
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