IF...THEN..ELSE statement

The IF..THEN..ELSE statement allows us to make the decision regarding program flow based on the result returned by an expression.

Syntax

LN IF expression (,) THEN statement(,) ELSE statement

• if the result of expression is true, the THEN statement is executed.
• if the result of expression is false, the THEN line number is ignored and the ELSE line number is executed.
• THEN and ELSE may be followed by either a line number for branching or one or more statements to be executed.
• IF..THEN..ELSE is a single statement. They must be written in one line.

Example

1. 10 IF A>B THEN PRINT "A is greater " ELSE PRINT "B is Greater"

It will print the message "A is Greater" if A is greater than B and will print "B is Greater" if B is greater than A  

Use of IF..THEN...ELSE statement in the program.
1. Write a program to decide whether a student has passed or failed in the exam. ( use IF...THEN..ELSE) Pass marks=32

CS 7.7 Display on the screen for IF..THEN..ELSE statement

Ok
10 REM Program to check whether a student is passed
15 REM or failed in the S.L..C. Exam
30 INPUT "Enter the marks obtained :" ;M
40 IF M>=32 THEN 45 ELSE 65
45 PRINT  "MARKS OBTAINED :"; M
50 PRINT "CONGRATULATIONS :"; HE PASSED
60 GOTO 80
65 PRINT "MARKS OBTAINED :"; M
70 PRINT "SORRY ! HE FAILED"
80 END
Ok
RUN
Enter the marks obtained : ? 76
Marks OBTAINED : 76
CONGRATULATIONS ! HE PASSED
Ok
RUN
Enter the marks obtained : ? 23
MARKS OBTAINED : 23
SORRY ! HE FAILED 

2. CS 7.8 Display on the screen for IF...THEN...ELSE statement

Ok
LIST 
10   CLS
15 REM Learning the use of IF...THEN..ELSE statemet
20 INPUT "ENTER THE FIRST NUMBER" ; X
30 INPUT "ENTER THE SECOND NUMBER" ; Y
40 INPUT "THE THIRD NUMBER" ; Z
50 IF X.>Y THEN GOTO 90 ELSE GOTO 100
90 IF X>Z THEN GOTO 130
95 GOTO 150
100 IF Y>Z THEN GOTO 140
105 GOTO 90
130 PRINT "THE LARGEST NUMBER IS" ; X
135 GOTO 160
140 PRINT "THE LARGEST NUMBER IS "; Y
145 GOTO 160
150 PRINT "THE LARGEST NUMBER IS"; Z
160 END
OK 
RUN