<< Chapter < Page Chapter >> Page >

Standard data types

The type of a variable determines how much space it occupies in storage and how the bit pattern stored is interpreted. Standard data types in C are listed in the following table:

Table of variable types
Variable Type Keyword Range Storage in Bytes
Character char -127 to 127 1
Unsigned character unsigned char 0 to 255 1
(Signed) integer int -32,768 to 32,767 2
Unsigned integer unsigned int 0 to 65,535 2
Short integer short -32,768 to 32,767 2
Unsigned short integer unsigned short 0 to 65,535 2
Long integer long -2,147,483,648 to 2,147,483,647 4
Unsigned long integerunsigned long 0 to 4,294,967,295 4
Single precision floating point float 1.2E-38 to 3.4E38, approx. range precision = 7 digits. 4
Double precision floating point double 2.2E-308 to 1.8E308, approx. range precision = 19 digits. 8

Declaration and usage of variables and constants


A variable is an object of a specified type whose value can be changed. In programming languages, a variable is allocated a storage location that can contain data that can be modified during program execution. Each variable has a name that uniquely identifies it within its level of scope.

In C, a variable must be declared before use , although certain declarations can be made implicitly by content. Variables can be declared at the start of any block of code, but most are found at the start of each function. Most local variables are created when the function is called, and are destroyed on return from that function.

A declaration begins with the type, followed by the name of one or more variables. Syntax of declare statement is described as:

data_type list_of_variables;

A list of variables includes one or many variable names separated by commas.

Single declarations

int age; //integer variable float amountOfMoney;//float variablechar initial;// character variable

Multiple declarations:

int age, houseNumber, quantity; float distance, rateOfDiscount;char firstInitial, secondInitial;
Got questions? Get instant answers now!

Variables can also be initialized when they are declared, this is done by adding an equals sign and the required value after the declaration.

int high = 250; //Maximum Temperature int low = -40; //Minimum Temperatureint results[20]; //Series of temperature readings
Got questions? Get instant answers now!


A constant is an object whose value cannot be changed. There are two method to define constant in C:

  • By #define statement. Syntax of that statement is:
#define constant_name value
#define MAX_SALARY_LEVEL 15 //An integer constant #define DEP_NAME “Computer Science”// A string constant
Got questions? Get instant answers now!
  • By using const keyword
const data_type variable_name = value;
const double e = 2.71828182845905;
Got questions? Get instant answers now!

Functions printf, scanf

Usually i/o, input and output, form the most important part of any program. To do anything useful your program needs to be able to accept input data and report back your results. In C, the standard library (stdio.h) provides routines for input and output. The standard library has functions for i/o that handle input, output, and character and string manipulation. Standard input is usually means input using the keyboard. Standard output is usually means output onto the monitor.

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?
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Introduction to computer science. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10776/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Introduction to computer science' conversation and receive update notifications?