PL/0 EBNF

Program ::= module Id ; Block Id .

Block ::= DeclList begin StmtList end

DeclList ::= { Decl ; }

Decl ::= ConstDecl | ProcDecl | VarDecl

ConstDecl ::= const ConstDeclItem { , ConstDeclItem }

ConstDeclItem ::= Id : Type = ConstExpr

ConstExpr ::= Id | Integer

VarDecl ::= var VarDeclItem { , VarDeclItem }

VarDeclItem ::= Id : Type

ProcDecl ::= procedure Id ([ FormalDecl {, FormalDecl} ] ) ; Block Id

FormalDecl::= Id : Type

Type ::= int

StmtList ::= { Stmt ; }

Stmt ::= CallStmt | AssignStmt | OutStmt | IfStmt | WhileStmt

CallStmt ::= Id ( [ Exprs ] )

AssignStmt::= Lvalue := Expr

Lvalue ::= Id

OutStmt ::= output := Expr

IfStmt ::= if Test then StmtList end

WhileStmt ::= while Test do StmtList end

Test ::= odd Sum | Sum Relop Sum

Relop ::= <= | <> | < | >= | > | =

Exprs ::= Expr {, Expr }

Expr ::= Sum

Sum ::= Term { (+ | -) Term }

Term ::= Factor { (* | /) Factor }

Factor ::= - Factor | LValue | Integer | input | ( Expr )