C uses a convenient abstraction called streams to perform input and output operations in sequential media such as the screen, the keyboard or a file. A stream is an entity where a program can either insert or extract characters to/from. There is no need to know details about the media associated to the stream or any of its internal specifications. C comes with libraries which provides us many ways for performing input and output. In C input and output is performed in the form of sequence of bytes or more commonly known as streams. Input Stream: If the direction of flow of bytes is from device(for example: Keyboard) to the main memory then this process is called input. Manipulators are helper functions that make it possible to control input/output streams using operator. (since C20) The manipulators that are invoked with arguments (e.g. Controls whether leading whitespace is skipped on input (function). When you say 'but the first index in array is the file path and the file contents is not displayed.' It sounds like you're trying to read input from argv and argc. The angle bracket shell operator does not work that way. Instead, stdin (what cin and several C functions read from) has the contents of that file. Aug 27, 2011 Concepts - Use of cin & cout for input & output - Use of variables - Use of string data type. Concepts - Use of cin & cout for input & output - Use of variables - Use of string data type.
For the input of specific types of variables in the C programming language, you’ll find that the scanf() function comes in handy. It’s not a general-purpose input function, and it has some limitations, but it’s great for testing code or grabbing values.
In a way, you could argue that scanf() is the input version of the printf() function. For example, it uses the same conversion characters (the % placeholder-things). Because of that, scanf() is quite particular about how text is input. Here’s the format:
Scary, huh? Gibson auto tuning guitar. Just ignore it for now. Here’s a less frightening version of the format:
In this version, placeholder is a conversion character, and variable is a type of variable that matches the conversion character. Unless it’s a string (char array), the variable is prefixed by the & operator.
The scanf() function is prototyped in the stdio.h header file, so you must include that file when you use the function.
Here are some scanf() examples:
The preceding statement reads an integer value into the variable highscore. This assumes that highscore is an int variable.
The preceding scanf() statement waits for a floating-point value to be input, which is then stored in the temperature variable.
In the preceding line, scanf() accepts the first character input and stores it in the key variable.
The %s placeholder is used to read in text, but only until the first white space character is encountered. So a space or a tab or the Enter key terminates the string. (That sucks.) Also, firstname is a char array, so it doesn’t need the & operator in the scanf() function.
How to read a string with scanf()![]()
One of the most common ways to put the scanf() function to use is to read in a chunk of text from standard input. To meet that end, the %s conversion character is used — just like in printf(), but with input instead of output.
SCANF() SWALLOWS A STRING
Exercise 1: Type the source code from scanf() Swallows a String into a new project, ex0712, in Code::Blocks. Build and run.
Line 5 declares a char array — a string variable — named firstname. The number in the brackets indicates the size of the array, or the total number of characters that can be stored there. The array isn’t assigned a value, so it’s created empty. Basically, the statement at Line 5 sets aside storage for up to 15 characters.
The scanf() function in Line 8 reads a string from standard input and stores it in the firstname array. The %s conversion character directs scanf() to look for a string as input, just as %s is a placeholder for strings in printf()’s output.
Exercise 2: Modify the source code from scanf() Swallows a String so that a second string is declared for the person’s last name. Prompt the user for their last name as well, and then display both names by using a single printf() function.
How to read values with scanf()
The scanf() function can do more than read strings. It can read in any value specified by a conversion character.
SCANF() EATS AN INTEGER
In scanf() Eats an Integer, the scanf() function reads in an integer value. The %d conversion character is used, just like printf() — indeed, it’s used in Line 9. That character directs scanf() to look for an int value for variable fav.
Exercise 3: Create a project, ex0714, using the source code shown in scanf() Eats an Integer. Build and run. Test the program by typing various integer values, positive and negative.
Perhaps you’re wondering about the ampersand (&) in the scanf() function. The character is a C operator — specifically, the memory address operator. It’s one of the advanced features in C that’s related to pointers. An ampersand must prefix any variable specified in the scanf() function. The exception is an array, such as the firstname char array in scanf() Eats an Integer.
Try running the program again, but specify a decimal value, such as 41.9, or type text instead of a number.
The reason you see incorrect output is that scanf() is very Little snitch for pc. specific. It fetches only the variable type specified by the conversion character. So if you want a floating-point value, you must specify a float variable and use the appropriate conversion character; %f, in that case.
Exercise 4: Modify the source code from scanf() Eats an Integer so that a floating-point number is requested, input, and displayed.
C++ File Input Output Example
Dev-C++ v 4.9.9.2 IDE
When I compile and run my program as a console project, a window flashes very briefly on the screen and disappears. The compile log says compilation was successful and execution terminated.
How to I keep the window (my output window?) from disappearing?
Ancient Dragon5,243Dev C++ Input And Outputs
You have to add a line just before the end of main() to stop the program from closing. Most people call getch() or c++ cin.get(), which is just waiting for keyboard entry.
Comments are closed.
|
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |