diff --git a/Makefile b/Makefile
index 7cc70560..e6d224a2 100644
--- a/Makefile
+++ b/Makefile
@@ -6,9 +6,13 @@ CFLAGS  += -Wall -Wextra
 
 CFILES = $(wildcard *.c)
 
+VPATH += src
+INCLUDES += src
+
 BUILD_NAME := $(shell git describe --long --always)
 DEFINES += BUILD_NAME='$(BUILD_NAME)'
-CPPFLAGS += $(patsubst %,-D%,$(DEFINES))
+CPPFLAGS += $(patsubst %,-D%,$(DEFINES)) \
+            $(patsubst %,-I%,$(INCLUDES))
 
 all: tas tsim
 tas: parser.o lexer.o
diff --git a/asm.c b/src/asm.c
similarity index 100%
rename from asm.c
rename to src/asm.c
diff --git a/asm.h b/src/asm.h
similarity index 100%
rename from asm.h
rename to src/asm.h
diff --git a/common.h b/src/common.h
similarity index 100%
rename from common.h
rename to src/common.h
diff --git a/lexer.l b/src/lexer.l
similarity index 100%
rename from lexer.l
rename to src/lexer.l
diff --git a/ops.h b/src/ops.h
similarity index 100%
rename from ops.h
rename to src/ops.h
diff --git a/parser.y b/src/parser.y
similarity index 100%
rename from parser.y
rename to src/parser.y
diff --git a/parser_global.h b/src/parser_global.h
similarity index 100%
rename from parser_global.h
rename to src/parser_global.h
diff --git a/tas.c b/src/tas.c
similarity index 94%
rename from tas.c
rename to src/tas.c
index 8b281569..d067e328 100644
--- a/tas.c
+++ b/src/tas.c
@@ -13,26 +13,6 @@
 
 int print_disassembly(FILE *out, struct instruction *i);
 
-static int binary_in(FILE *in, struct instruction *i)
-{
-    return fread(&i->u.word, 4, 1, in) == 1;
-}
-
-static int text_in(FILE *in, struct instruction *i)
-{
-    return fscanf(in, "%x", &i->u.word) == 1;
-}
-
-static int binary_out(FILE *stream, struct instruction *i)
-{
-    return fwrite(&i->u.word, sizeof i->u.word, 1, stream) == 1;
-}
-
-static int text_out(FILE *stream, struct instruction *i)
-{
-    return fprintf(stream, "0x%08x\n", i->u.word) > 0;
-}
-
 static const char shortopts[] = "df:o:p::hV";
 
 static const struct option longopts[] = {
diff --git a/tsim.c b/src/tsim.c
similarity index 100%
rename from tsim.c
rename to src/tsim.c