The ostream, istream, ofstream and ifstream classes
ifstream: Stream class to read from files ofstream: Just think that cin / cout is a part of istream / ostream that is used for standard input/output. inherits from istream, and the class ofstream (output file stream) inherits from The major difference between file streams and the two console streams is when. Recall that there is a difference between the ASCII character '1' and the internal Relationships among istream-ifstream; ostream-ofstream.
The unformatted output functions e. It converts a numeric value from its internal representation to the text form. It uses the terminating null character to decide the end of the char array. It also supports formatted input and unformatted input.
Can I use ifstream and istream both? - C++ Forum
In unformatting input, such as getgetlinreadit reads the characters as they are, without conversion. It performs formatting by converting the input texts into the internal representation of the respective types.
It uses whitespace as delimiter and adds a terminating null character to the C-string. Flushing the Input Buffer - ignore You can use the ignore to discard characters in the input buffer: The last input operation failed to read the expected characters or output operation failed to write the expected characters, e. Absence of above error with value of 0. However, it is more convenience to use these public member functions of ios class: By default, the values are displayed with a field-width just enough to hold the text, without additional leading or trailing spaces.
You need to provide spaces between the values, if desired.
For integers, all digits will be displayed, by default. This default precision of 6 digits include all digits before and after the decimal point, but exclude the leading zeros. Scientific notation E-notation will be used if the exponent is 6 or more or -5 or less. The default field-width is 0, i. The setw operation is non-sticky.
c++ - Difference between using ifstream and ofstream with cin and cout - Stack Overflow
That is, it is applicable only to the next IO operation, and reset back to 0 after the operation. The field-width property is applicable to both output and input operations. Except setwall the other IO manipulators are sticky, i. Floating point number can be display in 3 formatting modes: The precision is interpreted differently in default and non-default modes due to legacy. In default mode neither fixed nor scientific useda floating-point number is displayed in fixed-point notation e.
The precision in default mode includes digits before and after the decimal point but exclude the leading zeros. Fewer digits might be shown as the trailing zeros are not displayed. The default precision is 6. See the earlier examples for default mode with default precision of 6.
As mentioned, the trailing zeros are not displayed in default mode, you can use manipulator showpoint noshowpoint to show or hide the trailing zeros. In both fixed e. The default precision is also 6. Set the integral number base. The main point is simply to illustrate that different bit encodings are used for ASCII as opposed to binary file representations. External files can be opened in one of two ways. You can also use the get and put methods.
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When you are done reading from or writing to an external file, you should always close the file. That will allow the file to be reopened later in your program. Also — in the case of output files — it guarantees that everything you wrote actually gets flushed from internal buffers and written to disk: Similarly, ofstream is a special type of ostream.
In object-oriented terms, we say ifstream is a subclass or derived class of istream. Similarly, ofstream is a subclass or derived class of ostream. Any operation that can be performed on an istream ostream can also be applied to an ifstream ofstream.
Moreover, additional operations that are specific to the fact that the subclasses are associated with external files can be used. We have already seen explicit open and close methods, for example.
Whitespace is a contiguous sequence of one or more characters, each character of which is a blank, tab, carriage return, or line feed or perhaps other non-printable ASCII characters.
For example, if it is trying to read an integer, and the sequence of characters GHI is encountered on the input stream, the integer will be set toand the next byte to be read will be the 'G'.
If an error, the input stream is placed into an error state, and future input operations on that stream will not work.