10.4.2.9. IF~ELSEIF~ELSE~ENDIF

Explanation	Program is branched according to condition. Or, blocs after this statement are executed or not executed.
Grammar	Simple sentence IF	IF <condi.> THEN <addr.> [ELSE <addr.>] IF <condi.> THEN CALL <program No.> IF <condi.> THEN JMPP <program No.> IF <condi.> THEN GOSUB <addr.>
	Compound sentence IF	IF <condi.> THEN ~ [ELSEIF <condi.> THEN ~ ] [ELSE ~ ] ENDIF
Parameter	Condition	Arithmetic formula, string condition formula	If 0, true. If not, false.
	Address	THEN: If the condition is true, the address is branched. ELSE: If the condition is false, the address is branched.
Example	Example of simple sentence IF	IF V2!>SQR(V50!^2+V51!^2) THEN 150 ELSE *AGAIN
	Example of compound sentence IF	IF GI1>=10 THEN PRINT #0, "HIGH" PRINT #1, "HR-MSG: HIGH" ELSEIF GI1>=0 THEN PRINT #0, "LOW" ELSE GOTO *ERR ENDIF