Iostream library adalah object-oriented library yang menyediakan fungsi-fungsi input/output menggunakan stream.

Stream adalah sebuah abstraksi yang dapat diartikan sebuah device yang melakukan proses input/output. Stream juga dapat diartikan sebagai sumber atau tujuan dari karakter yang tidak terbatas.

Stream secara umum dapat diasosiasikan ke sumber atau tujuan dari karakter-karakter secara fisik, seperti disk file atau keyboard.

Elemen-elemen dari library iostream adalah :
Classes:

ios_base

Base class with type-independent members for the standard stream classes (class)

ios	Base class with type-dependent members for the standard stream classes (class)

istream

Input stream (class)

ostream

Output Stream (class)

iostream

Input/Output Stream (class)

ifstream

Input file stream class (class)

ofstream

Output file stream (class)

fstream

Input/output file stream class (class)

istringstream

Input string stream class (class)

ostringstream

Output string stream class (class)

stringstream

Input/output string stream class (class)

streambuf

Base buffer class for streams (class)

filebuf

File stream buffer (class)

stringbuf

String stream buffer (class)

Objects:

cin	Standard input stream (object)

cout	Standard output stream (object)

cerr	Standard output stream for errors (object)

clog	Standard output stream for logging (object)

Types:

fpos	Stream position class template (class template)

streamoff

Stream offset type (type)

streampos

Stream position type (type)

streamsize

Stream size type (types)

Manipulators:

boolalpha

Alphanumerical bool values (manipulator function)

dec	Use decimal base (manipulator function)

endl	Insert newline and flush (manipulator function)

ends	Insert null character (manipulator function)

fixed

Use fixed-point notation (manipulator function)

flush

Flush stream buffer (manipulator function)

hex	Use hexadecimal base (manipulator function)

internal

Adjust field by inserting characters at an internal position (manipulator function)

left	Adjust output to the left (manipulator function)

noboolalpha

No alphanumerical bool values (manipulator function)

noshowbase

Do not show numerical base prefixes (manipulator function)

noshowpoint

Do not show decimal point (manipulator function)

noshowpos

Do not show positive signs (manipulator function)

noskipws

Do not skip whitespaces (manipulator function)

nounitbuf

Do not force flushes after insertions (manipulator function)

nouppercase

Do not generate upper case letters (manipulator function)

oct	Use octal base (manipulator function)

resetiosflags

Reset format flags (manipulator function)

right

Adjust output to the right (manipulator function)

scientific

Use scientific notation (manipulator function)

setbase

Set basefield flag (manipulator function)

setfill

Set fill character (manipulator function)

setiosflags

Set format flags (manipulator function)

setprecision

Set decimal precision (manipulator function)

setw	Set field width (manipulator function)

showbase

Show numerical base prefixes (manipulator function)

showpoint

Show decimal point (manipulator function)

showpos

Show positive signs (manipulator function)

skipws

Skip whitespaces (manipulator function)

unitbuf

Flush buffer after insertions (manipulator function)

uppercase

Generate upper-case letters (manipulator function)

ws	Extract whitespaces (manipulator function)