01 · Scope

About VisuAlg

VisuAlg is an environment for writing and running algorithms in a Portuguese pseudolanguage, with its own teaching constructs. This reference brings together the syntax, functions, and teaching commands described in the author's manual for VisuAlg 3.0.5.2.

02 · Organization

Algorithm structure

An algorithm starts with the algoritmo keyword and a quoted name. Global declarations, a data file and subprograms appear before inicio; the main body ends with fimalgoritmo.

algoritmo "Welcome"
var
    nome: caractere
inicio
    escreva("What is your name? ")
    leia(nome)
    escreval("Hello, ", nome, "!")
fimalgoritmo

Braces do not delimit blocks. Structures use opening and closing keywords, such as se/fimse and enquanto/fimenquanto. The pseudolanguage uses one command per line.

For the file-reading extension, arquivo "data.txt" belongs in the declaration area before the main body. See Functions and helper commands.

03 · Writing

Names, comments and values

Keywords and variable names are case-insensitive; by convention, write keywords in lowercase without accents, such as entao and logico.
Names start with a letter and may continue with letters, digits or underscores. The reference manual sets a 30-character limit.
Line comments start with // and end at the line break. To comment multiple lines, start each line with its own marker.
Text literals use double quotes; decimal values use a period. Logical values are VERDADEIRO and FALSO.
One line represents one command; the pseudolanguage does not require semicolons to separate commands.

// names are case-insensitive
var
    nome_do_aluno: caractere
    nota: real
    aprovado: logico
inicio
    nota <- 8.5
    aprovado <- VERDADEIRO

04 · Data

Types, variables and assignment

Type	Use
`inteiro`	Whole numbers.
`real`	Numbers with a fractional part.
`caractere`	A character or a text string in double quotes.
`logico`	`VERDADEIRO` and `FALSO` values.

Variables are declared after var, with names on the left of the colon and the type on the right. Multiple names of the same type can be separated by commas. VisuAlg has no general keyword for declaring constants; fixed values appear as literals or expressions.

algoritmo "Declarations"
var
    tentativas, acertos: inteiro
    media: real
    nome: caractere
    terminou: logico
inicio
    tentativas <- 0
    media <- 7.25
    nome <- "Lia"
    terminou <- FALSO
fimalgoritmo

The assignment operator is <-; the left side is a variable or vector element, and the right side is an expression compatible with the target type. Use = to compare equality.

05 · Expressions

Operators and precedence

Group	Operators	Meaning
Assignment	`<-`	Stores an expression result in a variable.
Unary arithmetic	`+ -`	Indicates a positive or negative sign.
Exponentiation	`^`	Raises a base to an exponent.
Arithmetic	`* / \ MOD % + -`	Multiplication, real division, integer division, remainder, addition and subtraction. `\` performs integer division; `MOD` and `%` return the remainder.
Concatenation	`+`	Joins character-type expressions.
Relational	`= < > <= >= <>`	Equal, less than, greater than, less or equal, greater or equal and not equal.
Logical	`nao e ou xou`	Negation, conjunction, disjunction and exclusive disjunction.

In arithmetic, ^ has the highest precedence among binary operators; *, /, \ and % come before + and -. Unary signs have higher precedence. The manual identifies nao as the highest-precedence logical operator.

The reference manual does not publish a complete precedence table for all logical and relational operators. Use parentheses to make grouping explicit instead of relying on assumed conventions.

Text comparisons are case-insensitive; for example, the manual treats "ABC" and "abc" as equal.

06 · Interaction

Input, output and formatting

leia reads values into variables in the listed order. escreva displays comma-separated expressions; escreval does the same and then starts a new line.

algoritmo "Formatting"
var
    quantidade: inteiro
    preco: real
inicio
    escreva("Quantity: ")
    leia(quantidade)
    preco <- quantidade * 2.5
    escreval("Total: ", preco:8:2)
fimalgoritmo

For output, value:width reserves a field of the given width; real:width:decimals also sets the number of decimal places. Text is not automatically spaced like numeric expressions, so add spaces to the text where needed.

07 · Decisions

Conditions and selection

Use se ... entao to run a block when a logical expression is true. senao is optional and fimse closes the structure; conditions can be nested.

se nota >= 7 entao
    escreval("Passed")
senao
    escreval("Keep practicing")
fimse

escolha evaluates an expression once and compares its value with alternatives in each caso; outrocaso defines the default case. fimescolha closes the selection.

escolha opcao
caso 1, 2
    escreval("First option")
outrocaso
    escreval("Another option")
fimescolha

08 · Loops

Repetition

VisuAlg documents three main loops. para counts from the starting value through the limit, including it, with a default step of 1; a negative step counts down. The control variable must be an integer.

para indice de 1 ate 5 faca
    escreva(indice:3)
fimpara

enquanto quantidade > 0 faca
    quantidade <- quantidade - 1
fimenquanto

repita
    tentativas <- tentativas + 1
ate tentativas = 3

enquanto checks before its body and may run zero times. repita ... ate checks at the end and runs at least once. interrompa exits the current loop immediately.

An alternative form, repita ... fimrepita, has no final condition and requires interrompa to exit.

09 · Collections

Vectors and matrices

Indexed structures are declared with vetor and inclusive ranges. A vector can have one dimension and a matrix can have two. Bounds are constant integers, and the syntax gives the range for each dimension.

var
    notas: vetor[1..5] de real
    tabuleiro: vetor[0..2, 0..2] de caractere
inicio
    notas[1] <- 9.5
    tabuleiro[0, 1] <- "X"
    escreval(notas[1])
    escreval(tabuleiro[0, 1])

The number of elements in a dimension follows from its bounds, not from the final index alone. The first example has five positions indexed from 1 through 5; a range may also start at zero or another integer.

The VisuAlg manual documents vectors with up to two dimensions. Matrices are accessed with two comma-separated indices inside brackets.

10 · Reuse

Procedures and functions

Procedures and functions are declared after global variables and before inicio. A procedure returns no value; a function declares its return type after a colon and returns a result with retorne. Both may declare local variables in a var section.

algoritmo "Routines"
var
    resultado: inteiro
funcao dobro(valor: inteiro): inteiro
inicio
    retorne valor * 2
fimfuncao

procedimento somar(valor: inteiro; var total: inteiro)
inicio
    total <- total + valor
fimprocedimento

inicio
    resultado <- dobro(4)
    somar(3, resultado)
    escreval(resultado)
fimalgoritmo

Parameters separated by commas within one group share a type; different groups are separated by semicolons. Without var, a parameter is passed by value; with var, the routine may change the supplied variable. The manual supports recursion but does not allow nested routines.

Functions appear as expressions and procedures as statements. A procedure call without parameters may omit parentheses.

11 · Pseudolanguage resources

Functions and helper commands

The author's manual documents the input and output operations escreva, escreval and leia, as well as the math, trigonometric and text functions listed below. The signatures and behavior summarize the VisuAlg reference.

Group	Names	General use
Math	`Abs`, `ArcCos`, `ArcSen`, `ArcTan`, `Cos`, `CoTan`, `Exp`, `GraupRad`, `Int`, `Log`, `LogN`, `Pi`, `Quad`, `RadpGrau`, `RaizQ`, `Rand`, `RandI`, `Sen`, `Tan`	Values, angle conversion, integer part, logarithms, trigonometry, powers and random numbers.
Text and characters	`Asc`, `Carac`, `Caracpnum`, `Compr`, `Copia`, `Maiusc`, `Minusc`, `Numpcarac`, `Pos`	Convert characters and numbers, measure and extract text, change case and locate substrings.

Function signatures and results

Functions can be used in expressions or assigned to variables. Pi and Rand take no parameters; the other names show the number and order of their arguments.

Group	Signature	Result
Math	`Abs(expr)`, `Int(expr)`, `Quad(expr)`, `RaizQ(expr)`, `Exp(base, expoente)`, `Log(expr)`, `LogN(expr)`, `Pi`	Absolute value, integer part, square, square root, power, base-10 or natural logarithm, and the π constant.
Trigonometry	`Cos(expr)`, `CoTan(expr)`, `Sen(expr)`, `Tan(expr)`, `ArcCos(expr)`, `ArcSen(expr)`, `ArcTan(expr)`	Calculate trigonometric ratios and their inverse functions; input and output angles are in radians.
Angle conversion	`GraupRad(degrees)`, `RadpGrau(radians)`	Convert degrees to radians and radians to degrees.
Random values	`Rand`, `RandI(limit)`	`Rand` returns a real from 0 inclusive to 1 exclusive; `RandI` returns an integer from 0 inclusive up to, but not including, the limit.
Text and characters	`Asc(character)`, `Carac(code)`, `Caracpnum(string)`, `Numpcarac(number)`	Get the first character's ASCII code, convert a code to a character, text to a number, and a number to text.
Text and characters	`Compr(string)`, `Copia(string, start, count)`, `Pos(substring, string)`	Measure text, copy a number of characters, or find the first occurrence. Positions start at 1; `Pos` returns `0` when the substring is absent.
Text and characters	`Maiusc(string)`, `Minusc(string)`	Return text in uppercase or lowercase.

algoritmo "Function examples"
inicio
    escreval(abs(2 - 9))
    escreval(raizq(9))
    escreval(pos("Brasil", "Brasil e Portugal"))
fimalgoritmo

Output: 7, 3 and 1, each on its own line.

VisuAlg's reference also describes commands that support teaching and the environment:

aleatorio [on] activates the generation used by leia; with no range, numbers span 0 to 100 and characters are generated as five-letter uppercase strings. aleatorio maximum sets the inclusive range from 0 to the limit; aleatorio minimum, maximum sets both inclusive bounds. Both values must be numeric constants, not expressions; if reversed, VisuAlg swaps them. aleatorio off stops generation.
arquivo "path" associates reads with a text file and appears in the declaration section.
timer on enables the default 500 ms delay; timer <delay> sets an integer constant in milliseconds from 0 to 10,000, clamping values outside the range. Multiple timer commands are allowed in the command section. timer off disables the delay.
pausa pauses execution for inspection; debug condition pauses when the condition is true.
eco on|off controls whether input data is echoed to output; cronometro on|off measures elapsed time.
limpatela clears VisuAlg's simulated DOS screen but does not clear the main window's output panel.

12 · Example

Complete program

This example reads three grades, calculates their average and uses a function to classify the result:

algoritmo "Class average"
var
    nota1, nota2, nota3, media: real
funcao aprovado(media: real): logico
inicio
    retorne media >= 7
fimfuncao

inicio
    escreval("Enter three grades:")
    leia(nota1, nota2, nota3)
    media <- (nota1 + nota2 + nota3) / 3

    se aprovado(media) entao
        escreval("Passed with an average of ", media:5:2)
    senao
        escreval("Keep studying: average ", media:5:2)
    fimse
fimalgoritmo

13 · Reading tips

Common mistakes and how to avoid them

Using the wrong assignment symbol: in VisuAlg, <- assigns a value; = compares values in a condition.
Leaving a block open: each structure must end with its matching marker, such as fimse, fimpara, fimfuncao or fimalgoritmo.
Confusing an index with a count: vectors use their declared bounds; Copia(string, start, count) counts positions from 1 and its third argument is the number of characters to copy.
Expecting zero-based results from Pos: positions start at 1, and result 0 means the substring was not found.
Assuming the random limit is included: RandI(limit) returns values from zero up to, but not including, the limit. The aleatorio command uses inclusive ranges for input data.
Treating environment commands as functions: aleatorio, timer and debug are commands described by VisuAlg, not calls that return values.

When tracking down an error: check declaration order, variable types, vector bounds and block endings. In conditions, distinguish = (comparison) from <- (assignment).

14 · Further reading

VisuAlg references

The pseudolanguage manual distributed by VisuAlg's author, covering syntax, types, operators, commands, routines and teaching extensions; the command reference also details aleatorio and limpatela.
The numeric and text function catalog, with signatures and example results.
A copy of the manual in a university repository.

The manual presents VisuAlg syntax and teaching features. Consult the references to confirm function signatures and command behavior.

VisuAlg