diff --git a/bc/bc_parse.y b/bc/bc_parse.y
new file mode 100644
index 0000000..988ccaf
--- /dev/null
+++ b/bc/bc_parse.y
@@ -0,0 +1,139 @@
+%{
+  #include <stdio.h>
+
+  void yyerror(const char * str) {
+    /* 
+      str is the error message passed by YACC.
+      We'll want to reformat this at some point.
+    */
+    fprintf(stderr, "error: %s\n", str);
+  }
+
+  int yywrap(void) {
+    /* This is where passing to user control should go */
+    return 1;
+  }
+
+  main() {
+    yyparse();
+  }
+
+%}
+
+%union
+{
+  double number;
+  int num_op;
+  char letter_op;
+  char * string;
+}
+
+%token EOF NEWLINE 
+%token <string> STRING 
+%token <letter_op> LETTER 
+%token <number> NUMBER
+%token <letter_op> MUL_OP
+%token <num_op> ASSIGN_OP
+%token <num_op> REL_OP
+%token <num_op> INCR_DECR
+%token DEFINE BREAK QUIT LENGTH
+%token RETURN FOR IF WHILE SQRT
+%token SCALE IBASE OBASE AUTO
+%token OPAREN CPAREN OSQR CSQR OCURL CCURL
+%token COMMA SEMICOLON
+%token PLUS MINUS CARET
+
+%start program
+
+%%
+
+program         : EOF
+                | input_item program
+                ;
+
+input_item      : semicolon_list NEWLINE
+                | function
+                ;
+
+semicolon_list  : /* empty */
+                | statement
+                | semicolon_list SEMICOLON statement
+                | semicolon_list SEMICOLON
+                ;
+
+statement       : expression
+                | STRING
+                | BREAK
+                | QUIT
+                | RETURN
+                | RETURN OPAREN return_expression CPAREN
+                | FOR OPAREN expression SEMICOLON
+                          relational_expression SEMICOLON
+                          expression CPAREN statement
+                | IF OPAREN relational_expression CPAREN statement
+                | WHILE OPAREN relational_expression CPAREN statement
+                | OCURL statement_list CCURL
+                ;
+
+function        : DEFINE LETTER OPAREN opt_parameter_list CPAREN
+                        OCURL NEWLINE opt_auto_define_list
+                        statement_list CCURL
+                ;
+
+opt_parameter_list    : /* empty */
+                      | parameter_list
+                      ;
+
+parameter_list  : LETTER
+                | define_list COMMA LETTER
+
+opt_auto_define_list  : /* empty */
+                      | AUTO define_list NEWLINE
+                      | AUTO define_list SEMICOLON
+                      ;
+
+define_list     : LETTER
+                | LETTER OSQR CSQR
+                | define_list COMMA LETTER
+                | define_list COMMA LETTER OSQR CSQR
+                ;
+
+opt_argument_list     : /* empty */
+                      | argument_list
+                      ;
+
+argument_list   : expression
+                | LETTER OSQR CSQR COMMA argument_list
+                ;
+
+relational_expression : expression
+                      | expression REL_OP expression
+                      ;
+
+return_expression     : /* empty */
+                      | expression
+                      ;
+
+expression      : named_expression
+                | NUMBER
+                | OPAREN expression CPAREN
+                | LETTER OPAREN opt_argument_list CPAREN
+                | MINUS expression
+                | expression PLUS expression
+                | expression MINUS expression
+                | expression MUL_OP expression
+                | expression CARET expression
+                | INCR_DECR named_expression
+                | named_expression INCR_DECR
+                | named_expression ASSIGN_OP expression
+                | LENGTH OPAREN expression CPAREN
+                | SQRT OPAREN expression CPAREN
+                | SCALE OPAREN expression CPAREN
+                ;
+
+named_expression      : LETTER
+                      | LETTER OSQR expression CSQR
+                      | SCALE
+                      | IBASE
+                      | OBASE
+                      ;
\ No newline at end of file