Programmer's Guide to the Zeno Interpreter

The Zeno programming language provides several statements that control the sequence of program execution. Each of these control statements must be used entirely within the program module or a subprogram module.

Selection using if and case

These statements are used for conditional branching within a subprogram.

An if control statement has the form:

    if boolean expression then
        declarations and statements
   {elsif boolean expression then
        declarations and statements}
   [else
        declarations and statements]
    end if

The boolean expression for each branch is evaluated until one of them is true. The statements in the branch are executed until a closing elsif, else, or end if is reached. If no boolean expression is true then the statements following else, if present, are executed. The program resumes at the first statement after end if. An example:

program

    var mark : int

    get mark

    if mark > 100 then
        put "Invalid"
    elsif mark >= 93 then
        put 'A'
    elsif mark >= 85 then
        put 'B'
    elsif mark >= 78 then
        put 'C'
    elsif mark >= 70 then
        put 'D'
    else
        put 'F'
    end if

end program