Control Structures

Three Basic Control Structures

1. Sequence

Instructions executed one after another in order.

INPUT name
INPUT age
OUTPUT "Hello " + name
OUTPUT "You are " + age + " years old"
      

2. Selection (Decision)

Choosing different paths based on conditions.

IF-THEN-ELSE

IF score >= 50 THEN
    OUTPUT "Pass"
ELSE
    OUTPUT "Fail"
ENDIF
      

IF-THEN-ELSEIF-ELSE

IF score >= 80 THEN
    grade ← "A"
ELSEIF score >= 60 THEN
    grade ← "B"
ELSEIF score >= 50 THEN
    grade ← "C"
ELSE
    grade ← "F"
ENDIF
      

3. Iteration (Loops)

Repeating instructions multiple times.

FOR Loop (Count-controlled)

FOR i ← 1 TO 10
    OUTPUT i
ENDFOR
      

WHILE Loop (Pre-condition)

count ← 0
WHILE count < 5
    OUTPUT count
    count ← count + 1
ENDWHILE
      

REPEAT-UNTIL Loop (Post-condition)

REPEAT
    INPUT password
UNTIL password = "secret123"