diff --git a/lcthw/.ex10.argv b/lcthw/.ex10.argv
new file mode 100644
index 0000000..6c77829
--- /dev/null
+++ b/lcthw/.ex10.argv
@@ -0,0 +1,3 @@
+carrot
+angelfood
+yellow
diff --git a/lcthw/.ex13.argv b/lcthw/.ex13.argv
new file mode 100644
index 0000000..1c9f3d5
--- /dev/null
+++ b/lcthw/.ex13.argv
@@ -0,0 +1,5 @@
+garble
+geckle
+gimple
+gorble
+gunkle
diff --git a/lcthw/.gitignore b/lcthw/.gitignore
index 6add8a7..29a77ad 100644
--- a/lcthw/.gitignore
+++ b/lcthw/.gitignore
@@ -6,3 +6,4 @@ ex9
 ex10
 ex11
 ex12
+ex13
diff --git a/lcthw/Makefile b/lcthw/Makefile
index 8e85c60..8eb640d 100644
--- a/lcthw/Makefile
+++ b/lcthw/Makefile
@@ -1,11 +1,14 @@
 CFLAGS ?= -Wall -g
 GDBRUN = gdb --batch --ex run --ex bt --ex q --args
-BUILD_TARGETS = ex1 ex3 ex7 ex8 ex9 ex10 ex11 ex12
-TEST_TARGETS = ex1 ex3 ex7 ex8 ex9 ex11 ex12
+BUILD_TARGETS = $(foreach ex,$(wildcard ex*.c),$(subst .c,,$(ex)))
 
 .PHONY: all
 all: build test
 
+.PHONY: echo
+echo:
+	@echo BUILD_TARGETS=$(BUILD_TARGETS)
+
 .PHONY: clean
 clean:
 	rm -f $(BUILD_TARGETS)
@@ -15,16 +18,18 @@ build: $(BUILD_TARGETS)
 
 .PHONY: gtest
 gtest:
-	@$(foreach bt, $(TEST_TARGETS), make .gtest.$(bt) &&) \
+	@$(foreach bt, $(BUILD_TARGETS), make .gtest.$(bt) &&) \
 		printf '\ngYAY\n'
 
 .gtest.%:
+	@test_argv=$$(cat .$*.argv 2>/dev/null || echo) && \
 	printf '\n==> %s\n' "$*" && $(GDBRUN) ./$*
 
 .PHONY: test
 test:
-	@$(foreach bt, $(TEST_TARGETS), make .test.$(bt) &&) \
+	@$(foreach bt, $(BUILD_TARGETS), make .test.$(bt) &&) \
 		printf '\nYAY\n'
 
 .test.%:
-	printf '\n==> %s\n' "$*" && ./$*
+	@test_argv=$$(cat .$*.argv 2>/dev/null || echo) && \
+	printf '\n==> %s\n' "$*" && ./$* $$test_argv
diff --git a/lcthw/ex13.c b/lcthw/ex13.c
new file mode 100644
index 0000000..049c254
--- /dev/null
+++ b/lcthw/ex13.c
@@ -0,0 +1,25 @@
+#include <stdio.h>
+
+int main(int argc, char *argv[])
+{
+	int i = 0;
+	// go through each string in argv
+	// why am I skipping argv[0]?
+	for (i = 1; i < argc; i++) {
+		printf("arg %d: %s\n", i, argv[i]);
+	}
+
+	// let's make our own array of strings
+	char *states[] = {
+		"California", "Oregon",
+		"Washington", "Texas",
+	};
+
+	int num_states = 4;
+
+	for (i = 0; i < num_states; i++) {
+		printf("state %d: %s\n", i, states[i]);
+	}
+
+	return 0;
+}