Slide 1:C – Token: Individual words and punctuation words are called Tokens Keywords Identifiers Constants Strings Operators Special symbols


Slide 2:Keyword: C word is classified as either a key word or identifier All keywords have fixed meaning and meaning cannot be changed It serves as a basic building blocks of program statement All keywords must be written in lower case


Slide 3:Identifiers: It refers to the names of variables, functions and arrays These are user defined name and consist of sequence of letters and digits as first characters Both upper and lower cases are permitted Underscore (-) character is allowed in identifier. It is usually used as a link between two words in long identifier Constants: The value of the constants do not change during the execution of the program.


Slide 4:Constants Numeric constants Character constants Integer Real Single String Constant Constant character constant constant


Slide 5:Back slash character constant #include main() { printf(“Hello \n world”); } C supports some special back space character that are used in output function. Integer Constant: An integer constant refers to a sequence of digits. There are three types.


Slide 6:Decimal: It consist a set of digits 0 – 9 It is proceeded by an optional + (or) – sign Valid Eg: +823; -726; 0 Invalid Eg: #750;20,750;44 440


Slide 7:Octal: It consist of any combination of digits from the set 0 to 7 with a leading 0 Valid Eg: 037 0 0752


Slide 8:Hexa decimal: Sequence of digits proceeded by ox (or) OX is considered as hexa decimal integer. It includes alphabets A to F, to represent numbers 10-15 Valid Eg: OX2 ; OX9F


Slide 9:Real constants: Integer numbers are inadequate to represents quantities that vary continously such as distance, height, temperature, prices & soon. These quantities are represented by numbers containing fractional part. Such numbers are called real constants Eg: 0.004; -83 ------- Invalid -0.43; 254.0 ------ Invalid In above deciaml notation having a whole number followed by fractional part. It is possible to omit digits before and after the decimal points. Eg: 254, .04, +.21, -.54


Slide 10:Mantissa e exponent: Number in mantissa is either a floating point or integer. Exponent must be an integer number with the optional + or – sign. The letter e separating a mantissa and exponent can be written in lower or upper case. Examples: 2.75 e 4 - valid 12 e -2 - valid 1.5 e +5 - valid -1.2 e -1 - valid -52 e 62.5 - Invalid


Slide 11:Single character constant: A single character constant contains a single character enclosed within a pair of single quotes Example: ‘5’ , ‘1’ , ‘ ‘ Character constants have integer value known as ASCII value printf(“%d”, ‘a’); printf(“%c”,’97’);


Slide 12:String constant: A string constant is a sequence of character enclosed in double quotes Example: “welcome” “1884” “* - *” “5+3”


Slide 13:Sample program: (1) #include main() { printf(“%d”, size of (char)); printf(“%d”, size of (int)); printf(“%d”, size of (float)); } Output: 1 2 4


Slide 14:(2) #include main() { int i; int f; int c; printf(“%d”,size of (i)); printf(“%f “,size of (f)); printf(“%c”,size of (c)); }


Slide 15:(3) #include main() { char ch=291; printf(“%c”,ch); } Output: 291 The range of the character must be within the range of [ -128 to +127 ] So it is error