How to use Do, If, & Go TO structures in FORTRAN 77

IF Statements

Logical IF statement

IF statements execute conditional instructions. These statements make the program naughty. For every single task, it sets one condition in advance. If a particularly given condition (given by logical_expression) holds true, then only the program will execute a given statement (executable_statement).

IF (logical_expression) executable_statement

Block IF statement

The naughtiness of the program increases here. It says if this, then I will do this work, if not this, I will do that work and so one. So, the work it does depends upon the type of bribe. In this statement, optional one or multiple ELSE IF block follows a logical IF block.

GOTO Statements

GOTO statement causes the execution to jump to a labeled statement and resume the execution from there.

GOTO label

DO loops

It is a sequence of statements beginning with a DO statement. This loop allows giving the same set of instructions to a number of variables within a single go. This makes the program short and concise. The structure of a DO statement is as follows:

DO  label, Variable = e1, e2, e3

e1 is the starting variable, e2 is the ending variable and e3 is the spacing between two variables. For example, to use variables from 1 to 100 with a spacing of 5, we write

DO  10  VARIABLE = 1, 100, 5

However, e3 is optional. the label is the integer-valued label of continue command.