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I/O

See I/O example

See File stream example.

cout

Standard C++ output device (default: console).

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cout << "Some text" << endl;

cin

Standard C++ input device (default: keyboard).

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cin >> var;

endl

End of line.

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cout << "Some text" << endl;

ifstream

Open a file in read mode.

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ifstream file("file.txt");

Note

A file is closed at the end of a block.

ofstream

Open a file in write mode.

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ofstream file("file.txt");

Note

A file is closed at the end of a block.

append

Append data to an existing file.

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ofstream file("file.txt", append);

binary

Write a file in binary.

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ofstream file("file.btxt", binary);

seekg

Set the file position.

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file.seekg(Pos);

tellg

Get the file position.

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int Pos = file.tellg();

flush

Flush the buffer of the file.

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file.flush

getline

Get the current line.

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string s;
getline(file, s);

Output format

In the descriptions below, f is an output stream, for example cout or a ofstream.

All this methods, excepted the first, return a stream, so they can be chained:

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cout.scientific.showpos << 3 << endl;

precision

Set the number of digits printed to the right of the decimal point. This applies to all subsequent floating point numbers written to that output stream. However, this won’t make floating-point “integers” print with a decimal point. It’s necessary to use fixed for that effect.

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int np = f.precision(n)

scientific

Formats floating-point numbers in scientific notation

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f.scientific

fixed

Used fixed point notation for floating-point numbers. Opposite of scientific.

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f.fixed

showbase

Converts insertions to an external form that can be read according to the C++ lexical conventions for integral constants. By default, showbase is not set.

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f.showbase

noshowbase

Unset showbase flags.

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f.noshowbase

showpos

Inserts a plus sign (+) into a decimal conversion of a positive integral value.

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f.showpos

noshowpos

Unset showpos flags.

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f.noshowpos

default

Reset all the previous flags to the default expect precision.

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f.default

setw

Behaves as if member width were called with n as argument on the stream on which it is inserted as a manipulator (it can be inserted on output streams).

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f.setw(n)
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