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An introduction to file input and output with examples within the C++ programming language.

Overview of file i/o in c++

We need to understand how to open, read, write and close text files. The following File Input/Output terms are explained:

Text File – A file consisting of characters from the ASCII character code set. Text files (also know an ASCII text files) contain character data. When we create a text file we usually think of it consisting of a series of lines. On each line are several characters (including spaces, punctuation, etc.) and we generally end the line with a return (this a character within the ASCII character code set). The return is also known as the new line character. You are most likely already familiar with the escape code of \n which is used within C++ to indicate a return character when used with in a literal string with the cout.

A typical text file consisting of lines can be created by text editors (Notepad) or word processing programs (Microsoft Word). When using a word processor you must usually specify the output file as text (.txt) when saving it. Most source code files are ASCII text files with a unique file extension; such as C++ using .cpp, Pascal using .pas, Cobol using .cob, etc. Thus, most compiler/Integrated Development Environment software packages (such as the Bloodshed Dev-C++ 5 compiler/IDE ) can be used to create ASCII text files.

Filename – The name and its extension. Most operating systems have restrictions on which characters can be used in filenames. Example for MS-DOS and Windows: Lab_05.txt

Because some operating systems do not allow spaces, we suggest that you use the underscore where needed for spacing in a filename.

Filespec – The location of a file along with its filename. It is short for file specification. Most operating systems have a set of rules on how to specify the drive and directory (or path through several directory levels) along with the filename. Example for MS-DOS and Windows: C:\myfiles\cosc_1436\Lab_05.txt

Because some operating systems do not allow spaces, we suggest that you use the underscore where needed when creating folders or sub-directories.

Open – Your program requesting the operating system to let it have access to an existing file or to open a new file. Within C++ this is accomplished by including the header file:<fstream>File Input/Output is handled in C++ by using a pre-defined class of data objects, similar to the way string data type is handled. This class of objects has both data type names and functions built to specifically accomplish opening and closing a file.

Within your program you create a local storage variable with the data type of fstream like this:

fstream inData;

This variable will be used to store the device token that the operating system assigns to the file being opened. Thus, opening a file uses a class member function call like this:

inData.open("C:\\myfiles\\cosc_1436\\Lab_05.txt", ios::in);

The two parameters passed to the function are the filespec and the method that you want to use the file (in this example as input). The function provides a returning value of a device token from the operating system and it is stored in the variable named inData.

Questions & Answers

I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Programming fundamentals - a modular structured approach using c++. OpenStax CNX. Jan 10, 2013 Download for free at http://cnx.org/content/col10621/1.22
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