``` IF number<0 THEN PRINT "Negative number": GO TO 100: ELSE IF number>0 THEN PRINT "Positive number": GO TO 200: ELSE PRINT "The number is zero" : zero += 1: GO TO 300 ``` will allow you to jump to different parts of the program dependent on the results of the **IF...THEN...ELSE** statements; in this case, whether the number is negative, positive or zero (note that if the number is zero, one is added to the variable **zero** as well). **IF...THEN...ELSE** however only works within a single program line and as a consequence it can be bulky and even somewhat unreadable. For that reason a longer form variation exists: **IF** *condition* [**ELSE** [**IF** *condition*]] *action* **END IF** It is immediately apparent that there is no **THEN** clause. This is what determines if it's the long, medium or short form of the **IF** structure. Medium and short forms use **THEN** and are thus single program line structures whereas the absence of **THEN** makes it the long form one. The long form **IF** has some specific syntax requirements. First off **IF** *condition* needs to be the first statement on its line and so are **ELSE** and **ELSE IF**. Secondly, the whole **IF** structure's command' sequence must be terminated by an **END IF** (which also needs to be the first statement on its line). Consider this example: ``` 100 IF x>7:PRINT "x>7" 112 IF x>1000 113 PRINT "In fact it's huge" 114 ELSE 115 PRINT "But not too big" 116 ENDIF 120 ELSE IF x>3:PRINT "x>3 but x<=7" 140 ELSE IF x=3 150 PRINT "x=3" 160 ELSE 170 PRINT "x is too small to bother" 180 ENDIF ``` It vividly demonstrates how a combination of nesting **IF...ELSE...ENDIF** structures within an external superset of **IF...ELSE...ENDIF** can allow multiple decisions in an easy straightforward way. The main decision is contained in the initial **IF** on line 100 and the ensuing **ELSE** clause on line 160. There we're checking if **x** is greater than **7** or not. Obviously **x** can be smaller than **7** but how small is immaterial? This gets asked by the **ELSE IF** clauses on lines 120 and 140 where it's decided that for values from **3** (line 140) *up to and including* **7** (line 120) – the value *of greater than* **7** has been dealt with on line 100 as we saw – it does indeed matter. There is however a set of values that **x** can have that is *greater than* **7** and that's what the nested **IF...ELSE...ENDIF** structure on lines 112 through 116 allows us to test against where we further break it down to values *greater than* **1000** or *less or equal to* **1000** (but still greater than **7**). The **PRINT** statements are there to demonstrate there's actions we can take per decision and could easily have been **GO TO** or **INPUT** or other sets of keywords actually doing something according to the value of **x**. Moreover, there are two styles of writing on display here. The compact one (lines 100 and 120) and the more relaxed with lots whitespace one (lines 140 to 180).