C Tokens

• Identifiers• Keywords• Constants• Operators• Special symbols

Identifiers

• Identifiers are names given to various program elements such as variables, functions and arrays etc,.

• Eg: #define N 10#define a 15 Here N and a are user defined identifiers.

Rules for naming identifier• First character must be alphabetic or underscore.• Must consist only of alphabetic characters, digits, or

underscores.• Only the first 31 characters of an identifier are

significant and are recognized by the compiler.• Cannot use a keywords or reserved word (e.g. main,

include, printf & scanf etc.).• No space are allowed between the identifiers etc,.• C is case sensitive, e.g. My_name my_name.

Examples of Valid and Invalid Names

Valid Names Invalid Names

a a1 $sum /* $ is illegal */

student_name stdntNm 2names /* Starts with 2 */

_aSystemName _anthrSysNm stdnt Nmbr /* no spaces */

TRUE FALSE int /* reserved word */

Variables

• Variable is an identifier that is used to represent some specified type of information.

• Eg: x=3• Here x is variable.

Keywords

• It is a reserved words.• Cannot be used for anything else.• Examples:

– int– while– for etc,.

KeywordsAuto register ContinueDouble typedef ForInt Char signedStruct extern void Break return Default Else union GotoLong Const sizeof Switch Float doCase short IfEnum unsignedStatic While

Constants

• It is an entity whose value does not changes during the execution.

• Eg: x=3• Here 3 is a constant.

Types

• Numeric constants• Character constant

Constants

Constants

Character Constants Numeric Constants

RealConstant

IntegerConstant

String Constant

SingleCharacter Constant

Numeric constantsInteger constants• It is formed using a sequence of digits.

Decimal - 0 to 9 .Octal - 0 to 7.Hexa - 0 to 9 ,A to F

Eg: 10,75 etc.

Rules for defining Integer Constant

• It must have atleast one digit.• Decimal point are not allowed.• No blank space or commas are allowed.• It can be either positive or negative. Etc,.

Numeric constants

Real constants• It is formed using a sequence of digits but it

contain decimal point.• length, height, price distance measured in real

number Eg: 2.5, 5.11, etc.

Character constants

Single character constant– A character constant is a single character they also

represented with single digit or a single special symbol which is enclosed in single quotes.

– Eg: ‘a’, ‘8’,’_’etc.

Character constants

String constants• String constant are sequence of characters enclosed

with in double quote.• Eg: “Hello” ,”444”,”a” etc,.

Operators

• An operator is a symbol that specifies an operation to be performed on the operands.

• Eg: a + b+ is an operator.a,b are operands.

Data Types

· A Data type is the type of data that are going to access within the program.

Standard Data Types

These Standard type can be used to build more complex data types called Derived Types (e.g. pointers, array, union etc.).

Data typesData type Size(bytes) Range Format string

Char 1 -128 to 127 %c

int 2 -32,768 to 32,767 %d

Float 4 3.4 e-38 to 3.4 e+38 %f

Double 8 1.7 e-308 to 1.7 e+308 %lf

integer A number without a fraction part : integral

number. C supports three different sizes of the integer

data type :short intintlong int

Floating Point A floating-point type is a number with a

fractional part, e.g. 56.78 Floating point numbers are stored using 4 Byte. Types

Float Double long double

character

• Character are generally stored using 8 bits(1 Byte) of the internal storage.

Character ASCII code value

a 97(decimal) or 01100001(binary)

x 120(decimal) or 01111000(binary)

void The void type has no values and no operations. Both the set of values and the set of operations

are empty.

Variable’s Declaration

To create a variable, you must specify the type and then its identifier :

float price;int a,b;char code;

Entire Data types in c:Data type Size(bytes) Range Format string

Char 1 128 to 127 %c

Unsigned char 1 0 to 255 %c

Short or int 2 -32,768 to 32,767 %i or %d

Unsigned int 2 0 to 65535 %u

Long 4 -2147483648 to 2147483647 %ld

Unsigned long 4 0 to 4294967295 %lu

Float 4 3.4 e-38 to 3.4 e+38 %f or %g

Double 8 1.7 e-308 to 1.7 e+308 %lf

Long Double 10 3.4 e-4932 to 1.1 e+4932 %lf