data structures using numeric variables numeric variables can be used to store either integer values or floating point values modifiers like shortlongsignedand unsigned can also be used with numeric variables the difference between signed and unsigned numeric variables is that signed variables can be either negative or positive but unsigned variables can only be positive thereforeby using an unsigned variable we can increase the maximum positive range when we omit the signed/unsigned modifierc language automatically makes it signed variable to declare an unsigned variablethe unsigned modifier must be explicitly added during the declaration of the variable character variables character variables are just single characters enclosed within single quotes these characters could be any character from the ascii character set--letters (' '' ')numerals (' ')or special characters ('&'declaring variables to declare variablespecify the data type of the variable followed by its name the data type indicates the kind of values that the variable can store variable names should always be meaningful and must reflect the purpose of their usage in the program in cvariable declaration always ends with semi-colon for exampleint emp_numfloat salarychar gradedouble balance_amountunsigned short int acc_noin cvariables can be declared at any place in the program but two things must be kept in mind firstvariables should be declared before using them secondvariables should be declared closest to their first point of use so that the source code is easier to maintain initializing variables while declaring the variableswe can also initialize them with some value for exampleint emp_num float salary char grade ' 'double balance_amount constants constants are identifiers whose values do not change while values of variables can be changed at any timevalues of constants can never be changed constants are used to define fixed values like pi or the charge on an electron so that their value does not get changed in the program even by mistake declaring constants to declare constantprecede the normal variable declaration with const keyword and assign it value const float pi