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Imperative Paradigm

The imperative paradigm languages are fully specified and algorithmic in nature. Imperative languages specify the data (variables), and changes to the data via the flow of control (control structures).

In imperative languages – such as Pascal , FORTRAN, COBOL, C, Ada and Visual Basic – each data item should be declared, indicating the variable’s purpose by using a meaningful name, and specifying the data type.

Imperative languages have predefined data types of integer, float or real, character, string, array and record. This is because once a variable has been defined with a given data type it then must be used accordingly.

With a declaration of
Count : integer

only whole numbers can be assigned to the variable Count. If an attempt is made to assign the value 2.3 to Count then a run time or type mismatch error occurs.

It is important to note that imperative languages are destructive of variables values. That is, a program can reassign a value to a variable. The following line is common within many languages
Count := Count + 1

How the program is to be executed is determined by the control structures of sequence, selection (IF … ENDIF and CASEWHERE … ENDCASE) and repetition (FOR … NEXT, WHILE … ENDWHILE and REPEAT … UNTIL).