Programs become interesting when they react to data. In VisuAlg, decisions use the se structure, which reads almost like plain Portuguese: se (if) a condition is true, entao (then) do something, senao (else) do something different.
The simple form
se idade >= 18 entao
escreval("Maior de idade")
fimseEvery se must close with fimse. Forgetting it is the most common syntax error in conditional code.
Adding an alternative
algoritmo "aprovacao"
var
n1, n2, media: real
inicio
leia(n1, n2)
media <- (n1 + n2) / 2
se media >= 7 entao
escreval("Aprovado com media ", media:4:1)
senao
escreval("Em recuperacao")
fimse
fimalgoritmoComparison and logical operators
| Operator | Meaning |
|---|---|
= | equal to |
<> | different from |
> < >= <= | greater, less, greater or equal, less or equal |
e | both conditions must be true |
ou | at least one must be true |
nao | inverts the result |
se (nota >= 7) e (faltas <= 10) entao
escreval("Aprovado")
fimseUse parentheses around each comparison when you combine them. It makes the order of evaluation obvious to you and to the interpreter.
Nested decisions
You can place one se inside another to test several ranges:
se media >= 7 entao
escreval("Aprovado")
senao
se media >= 4 entao
escreval("Recuperacao")
senao
escreval("Reprovado")
fimse
fimseMany options with escolha
When you compare one variable against several fixed values, escolha is cleaner than a stack of nested se blocks:
escolha opcao
caso 1
escreval("Somar")
caso 2
escreval("Subtrair")
caso 3, 4
escreval("Multiplicar ou dividir")
outrocaso
escreval("Opcao invalida")
fimescolhaDraw the flowchart first. A diamond for each condition and an arrow for each outcome shows you whether a branch is missing before you write a single line.
Practice ideas
- Read three numbers and print the largest.
- Classify a triangle as equilateral, isosceles or scalene.
- Build a menu with
escolhafor a simple calculator.
Next step: repeat actions automatically with loops in VisuAlg.
