diff --git a/src/ast.zig b/src/ast.zig
new file mode 100644
index 0000000..1ed62f4
--- /dev/null
+++ b/src/ast.zig
@@ -0,0 +1,19 @@
+pub const AstNodeType = enum {
+    Program,
+};
+
+pub const AstNode = union(AstNodeType) {
+    Program: []AstNode,
+};
+
+pub fn printNode(stdout: var, node: AstNode) anyerror!void {
+    switch (node) {
+        .Program => |children| try printNodes(stdout, children),
+    }
+}
+
+fn printNodes(stdout: var, nodes: []AstNode) anyerror!void {
+    for (nodes) |node| {
+        try printNode(stdout, node);
+    }
+}
diff --git a/src/main.zig b/src/main.zig
index e538343..b9ca981 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,6 +1,6 @@
 const std = @import("std");
 
-const scanners = @import("scanner.zig");
+const runners = @import("runner.zig");
 
 const Allocator = std.mem.Allocator;
 
@@ -9,30 +9,14 @@ pub const Result = error{
     CompileError,
 };
 
+pub const StdOut = *std.io.OutStream(std.fs.File.WriteError);
+
 fn run(allocator: *Allocator, data: []u8) !void {
     var stdout_file = try std.io.getStdOut();
     const stdout = &stdout_file.outStream().stream;
 
-    var scanner = scanners.Scanner.init(allocator, data);
-
-    while (true) {
-        var tok_opt = scanner.nextToken() catch |err| {
-            try stdout.print(
-                "error at '{}': {}\n",
-                scanner.currentLexeme(),
-                err,
-            );
-
-            return Result.CompileError;
-        };
-
-        if (tok_opt) |tok| {
-            if (tok.ttype == .EOF) break;
-            try stdout.print("{x}\n", tok);
-        }
-    }
-
-    return Result.Ok;
+    var runner = runners.Runner.init(allocator, stdout);
+    return runner.execute(data);
 }
 
 fn runFile(allocator: *Allocator, path: []const u8) !void {
diff --git a/src/parser.zig b/src/parser.zig
new file mode 100644
index 0000000..e57d0ec
--- /dev/null
+++ b/src/parser.zig
@@ -0,0 +1,72 @@
+const std = @import("std");
+const scanners = @import("scanner.zig");
+const main = @import("main.zig");
+const ast = @import("ast.zig");
+const tokens = @import("tokens.zig");
+
+const Allocator = std.mem.Allocator;
+const Scanner = scanners.Scanner;
+const AstNode = ast.AstNode;
+const Token = tokens.Token;
+const TokenType = tokens.TokenType;
+const Result = main.Result;
+
+pub const Parser = struct {
+    allocator: *Allocator,
+    scanner: *Scanner,
+    current: Token = undefined,
+    root: AstNode = undefined,
+
+    pub fn init(allocator: *Allocator, scanner: *Scanner) Parser {
+        return Parser{ .allocator = allocator, .scanner = scanner };
+    }
+
+    fn doError(self: *Parser, comptime fmt: []const u8, args: ...) !void {
+        std.debug.warn("parser error at line {}\n\t", self.scanner.line);
+        std.debug.warn(fmt, args);
+        std.debug.warn("\n");
+
+        return Result.CompileError;
+    }
+
+    fn advance(self: *Parser) !void {
+        var tok_opt = try self.scanner.nextToken();
+        if (tok_opt) |tok| {
+            self.current = tok;
+        }
+    }
+
+    fn accept(self: *Parser, ttype: TokenType) !bool {
+        if (self.current.ttype == ttype) {
+            try self.advance();
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    fn expect(self: *Parser, ttype: TokenType) !void {
+        if (!try self.accept(ttype)) {
+            try self.doError("expected {x}, got {}", ttype, self.current.ttype);
+        }
+    }
+
+    fn program(self: *Parser) !void {
+        try self.advance();
+        try self.advance();
+        try self.advance();
+        try self.advance();
+
+        try self.expect(.EOF);
+    }
+
+    pub fn parse(self: *Parser) !AstNode {
+        self.root = AstNode{
+            .Program = try self.allocator.alloc(AstNode, 0),
+        };
+
+        try self.program();
+
+        return self.root;
+    }
+};
diff --git a/src/runner.zig b/src/runner.zig
new file mode 100644
index 0000000..61c0af1
--- /dev/null
+++ b/src/runner.zig
@@ -0,0 +1,48 @@
+const std = @import("std");
+const scanners = @import("scanner.zig");
+const parsers = @import("parser.zig");
+const main = @import("main.zig");
+const ast = @import("ast.zig");
+
+const Allocator = std.mem.Allocator;
+const Result = main.Result;
+const Parser = parsers.Parser;
+
+pub const Runner = struct {
+    allocator: *Allocator,
+    stdout: main.StdOut,
+
+    pub fn init(allocator: *Allocator, stdout: main.StdOut) Runner {
+        return Runner{ .allocator = allocator, .stdout = stdout };
+    }
+
+    fn testScanner(self: *Runner, scanner: *scanners.Scanner) !void {
+        while (true) {
+            var tok_opt = scanner.nextToken() catch |err| {
+                try self.stdout.print(
+                    "error at '{}': {}\n",
+                    scanner.currentLexeme(),
+                    err,
+                );
+
+                return Result.CompileError;
+            };
+
+            if (tok_opt) |tok| {
+                if (tok.ttype == .EOF) break;
+                try self.stdout.print("{x}\n", tok);
+            }
+        }
+    }
+
+    pub fn execute(self: *Runner, code: []u8) !void {
+        var scanner = scanners.Scanner.init(self.allocator, code);
+        try self.testScanner(&scanner);
+
+        scanner = scanners.Scanner.init(self.allocator, code);
+        var parser = Parser.init(self.allocator, &scanner);
+        var tree = try parser.parse();
+        try ast.printNode(self.stdout, tree);
+        return Result.Ok;
+    }
+};