diff --git a/c1/exercises/a.out.dSYM/Contents/Info.plist b/c1/exercises/a.out.dSYM/Contents/Info.plist
new file mode 100644
index 0000000..3679a65
--- /dev/null
+++ b/c1/exercises/a.out.dSYM/Contents/Info.plist
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+	<dict>
+		<key>CFBundleDevelopmentRegion</key>
+		<string>English</string>
+		<key>CFBundleIdentifier</key>
+		<string>com.apple.xcode.dsym.a.out</string>
+		<key>CFBundleInfoDictionaryVersion</key>
+		<string>6.0</string>
+		<key>CFBundlePackageType</key>
+		<string>dSYM</string>
+		<key>CFBundleSignature</key>
+		<string>????</string>
+		<key>CFBundleShortVersionString</key>
+		<string>1.0</string>
+		<key>CFBundleVersion</key>
+		<string>1</string>
+	</dict>
+</plist>
diff --git a/c1/exercises/a.out.dSYM/Contents/Resources/Relocations/aarch64/a.out.yml b/c1/exercises/a.out.dSYM/Contents/Resources/Relocations/aarch64/a.out.yml
new file mode 100644
index 0000000..3cb936a
--- /dev/null
+++ b/c1/exercises/a.out.dSYM/Contents/Resources/Relocations/aarch64/a.out.yml
@@ -0,0 +1,7 @@
+---
+triple:          'arm64-apple-darwin'
+binary-path:     a.out
+relocations:
+  - { offset: 0x26, size: 0x8, addend: 0x0, symName: _main, symObjAddr: 0x0, symBinAddr: 0x100003F38, symSize: 0x30 }
+  - { offset: 0x41, size: 0x8, addend: 0x0, symName: _main, symObjAddr: 0x0, symBinAddr: 0x100003F38, symSize: 0x30 }
+...
diff --git a/c1/exercises/compile_commands.json b/c1/exercises/compile_commands.json
new file mode 100644
index 0000000..fe51488
--- /dev/null
+++ b/c1/exercises/compile_commands.json
@@ -0,0 +1 @@
+[]
diff --git a/c1/exercises/main.c b/c1/exercises/main.c
new file mode 100644
index 0000000..2097858
--- /dev/null
+++ b/c1/exercises/main.c
@@ -0,0 +1,56 @@
+#include "util.h"
+#include <string.h>
+#include <stdio.h>
+
+typedef struct tree *T_tree;
+struct tree {
+	T_tree left;
+	string key;
+	T_tree right;
+};
+T_tree Tree(T_tree l, string k, T_tree r)
+{
+	T_tree t = checked_malloc(sizeof(*t));
+	t->left = l;
+	t->key = k;
+	t->right = r;
+	return t;
+}
+
+T_tree insert(string key, T_tree t)
+{
+	if (t == NULL)
+		return Tree(NULL, key, NULL);
+	else if (strcmp(key, t->key) < 0)
+		return Tree(insert(key, t->left), t->key, t->right);
+	else if (strcmp(key, t->key) > 0)
+		return Tree(t->left, t->key, insert(key, t->right));
+	else
+		return Tree(t->left, key, t->right);
+}
+
+bool member(string key, T_tree t)
+{
+	if (t == NULL) {
+		return FALSE;
+	}
+
+	if (strcmp(t->key, key) == 0) {
+		return TRUE;
+	}
+
+	return member(key, t->left) || member(key, t->right);
+}
+
+int main(int argc, char *argv[])
+{
+	string values[] = { "t", "s", "p", "i", "p", "f", "b", "s", "t" };
+
+	T_tree tree;
+
+	for (int i = 0; i < 9; i++) {
+		tree = insert(values[i], tree);
+	}
+
+	printf("member: %d\n", member("t", tree));
+}
diff --git a/c1/exercises/makefile b/c1/exercises/makefile
new file mode 100644
index 0000000..b03fb0a
--- /dev/null
+++ b/c1/exercises/makefile
@@ -0,0 +1,11 @@
+all: main.o util.o
+	gcc -g main.o util.o
+
+main.o: main.c util.h
+	gcc -g -c main.c util.h
+
+util.o: util.c util.h
+	gcc -g -c util.c
+
+clean:
+	rm -f a.out util.o prog1.o slp.o main.o
diff --git a/c1/exercises/util.c b/c1/exercises/util.c
new file mode 100644
index 0000000..e6445d6
--- /dev/null
+++ b/c1/exercises/util.c
@@ -0,0 +1,16 @@
+#include <stdlib.h>
+#include <strings.h>
+#include "util.h"
+string String(char *s)
+{
+  string p = checked_malloc(strlen(s)+1);
+  strcpy(p,s);
+  return p;
+}
+
+void *checked_malloc(int len)
+{
+	void *p = malloc(len);
+	assert(p);
+	return p;
+}
diff --git a/c1/exercises/util.h b/c1/exercises/util.h
new file mode 100644
index 0000000..c1476b5
--- /dev/null
+++ b/c1/exercises/util.h
@@ -0,0 +1,16 @@
+#ifndef UTIL_H
+#define UTIL_H
+
+#include <assert.h>
+
+typedef char *string;
+string String(char *);
+
+typedef char bool;
+#define TRUE 1;
+#define FALSE 0;
+
+void *checked_malloc(int);
+
+#endif // !UTIL_H
+
diff --git a/c1/exercises/util.h.gch b/c1/exercises/util.h.gch
new file mode 100644
index 0000000..e35006a
Binary files /dev/null and b/c1/exercises/util.h.gch differ