Informal specification of the Tiny language

A Tiny program is a sequence of statements separated by semicolons.  
There are no procedures or declarations. 
   
There are two control statements: an if-statement and a repeat-statement.  
Both control statements may themselves contain statement sequences.  
An if-statement has an optional else-part, and must be terminated by 
the keyword "end".  Input and output are performed by read and write
statements.  Non-nested comments are contained between braces.

Tiny expressions are either Boolean or integer.  Noolean expression
are constructed using < and = operators.  Boolean expressions may only 
be used in control statements.  Arithmetic expressions are constructed
recursively using operators +, -, * and /, and parentheses.

All variables are integer-valued.

Here is a sample program:

{ Sample Tiny program - computes factorial }
read x; { input an integer x }
if x > 0 then 
    fact := 1;
    repeat
        fact = fact * x;
        x := x - 1;
    until x = 0;
    write fact { output factorial of x }
end