diff --git a/src/cpu.c b/src/cpu.c
new file mode 100644
index 0000000..b14ba35
--- /dev/null
+++ b/src/cpu.c
@@ -0,0 +1,39 @@
+#include "cpu.h"
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+char const* const cpu_path = "/sys/devices/system/cpu/cpu%i/online";
+
+bool getcore(uint32_t id) {
+	// get the file path
+	char path[64];                    // contains the file path (max length is 64 due to the path and a bunch of extra wiggle room)
+	snprintf(path, 64, cpu_path, id); // writes the path using the id
+
+	// if the file doesn't exist; return true
+	if (access(path, R_OK) != 0)
+		return true;
+
+	// read a character from the file, store in state
+	char state = '\0';
+	FILE* f = fopen(path, "r");
+	fread(&state, 1, 1, f);
+	fclose(f);
+
+	// return whether state is truthy
+	return !!state;
+}
+
+void setcore(uint32_t id, bool state) {
+	char path[64];
+	snprintf(path, 64, cpu_path, id);
+
+	char s = 0x30 + (char)state; // convert the state to a character
+
+	// write the state to the file (creates file if it doesn't exist)
+	FILE* f = fopen(path, "w");
+	fwrite(&s, 1, 1, f);
+	fclose(f);
+}
diff --git a/src/cpu.h b/src/cpu.h
new file mode 100644
index 0000000..c434ca8
--- /dev/null
+++ b/src/cpu.h
@@ -0,0 +1,6 @@
+#pragma once
+#include <stdbool.h>
+#include <stdint.h>
+
+bool getcore(uint32_t);       // gets the state of core (id)
+void setcore(uint32_t, bool); // sets the state of core (id)
diff --git a/src/error.c b/src/error.c
new file mode 100644
index 0000000..ef9881b
--- /dev/null
+++ b/src/error.c
@@ -0,0 +1,18 @@
+#include "error.h"
+
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdnoreturn.h>
+
+noreturn void fatal(char const* fmt, ...) {
+	char buf[128];
+	va_list args;
+	va_start(args, fmt);
+	vsnprintf(buf, 128, fmt, args);
+	va_end(args);
+
+	fprintf(stderr, "\033[91mE: %s\033[0m\n", buf);
+	exit(1);
+}
diff --git a/src/error.h b/src/error.h
new file mode 100644
index 0000000..e3d2a56
--- /dev/null
+++ b/src/error.h
@@ -0,0 +1,7 @@
+#pragma once
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdnoreturn.h>
+
+// prints an error message and aborts execution
+noreturn void fatal(char const*, ...);
diff --git a/src/main.c b/src/main.c
index 7c01c7f..b352667 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,99 +1,12 @@
-#include <getopt.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
 #include <stdnoreturn.h>
 #include <sys/sysinfo.h>
 #include <unistd.h>
 
-enum opt {
-	OPT_LIST_CORES = 1, // option that lists the total amount of cores that are set
-	OPT_SET_ALL = 2,    // option to set all cores, regardless of their assumed state
-	OPT_VERBOSE = 4,    // print which cores are disabled/enabled
-	OPT_INVERT = 8,     // 'num' now represents the amount of cores to disable
-};
-
-char const* const cpu_path = "/sys/devices/system/cpu/cpu%i/online";
-
-noreturn void fatal(char const* fmt, ...) {
-	char buf[128];
-	va_list args;
-	va_start(args, fmt);
-	vsnprintf(buf, 128, fmt, args);
-	va_end(args);
-
-	fprintf(stderr, "\033[91mE: %s\033[0m\n", buf);
-	exit(1);
-}
-
-uint8_t getoptions(int32_t argc, char* const* argv, int32_t* ncpus) {
-	uint8_t opts = 0;
-	char opt;
-
-	char const* const msg = "-%c has already been set";
-	while ((opt = getopt(argc, argv, "lavi")) != -1) {
-		switch (opt) {
-		case 'l':
-			if (opts & OPT_LIST_CORES) fatal(msg, 'l');
-			opts |= OPT_LIST_CORES;
-			break;
-		case 'a':
-			if (opts & OPT_SET_ALL) fatal(msg, 'a');
-			opts |= OPT_SET_ALL;
-			break;
-		case 'v':
-			if (opts & OPT_VERBOSE) fatal(msg, 'v');
-			opts |= OPT_VERBOSE;
-			break;
-		case 'i':
-			if (opts & OPT_INVERT) fatal(msg, 'i');
-			opts |= OPT_INVERT;
-			break;
-		case '?':
-			fatal("usage: %s [number] [-l] [-a] [-v] [-i]", argv[0]);
-		}
-	}
-
-	if (optind < argc) {
-		char* num = argv[optind];
-		*ncpus = atoi(num);
-	} else fatal("you must provide a number!");
-
-	return opts;
-}
-
-bool getcore(uint32_t id) {
-	// get the file path
-	char path[64];                    // contains the file path (max length is 64 due to the path and a bunch of extra wiggle room)
-	snprintf(path, 64, cpu_path, id); // writes the path using the id
-
-	// if the file doesn't exist; return true
-	if (access(path, R_OK) != 0)
-		return true;
-
-	// read a character from the file, store in state
-	char state = '\0';
-	FILE* f = fopen(path, "r");
-	fread(&state, 1, 1, f);
-	fclose(f);
-
-	// return whether state is truthy
-	return !!state;
-}
-
-void setcore(uint32_t id, bool state) {
-	char path[64];
-	snprintf(path, 64, cpu_path, id);
-
-	char s = 0x30 + (char)state; // convert the state to a character
-
-	// write the state to the file (creates file if it doesn't exist)
-	FILE* f = fopen(path, "w");
-	fwrite(&s, 1, 1, f);
-	fclose(f);
-}
+#include "error.h"
+#include "opts.h"
 
 int32_t main(int32_t argc, char** argv) {
 	if (geteuid() != 0) fatal("must be executed as the root user!");
diff --git a/src/opts.c b/src/opts.c
new file mode 100644
index 0000000..52787a2
--- /dev/null
+++ b/src/opts.c
@@ -0,0 +1,43 @@
+#include "opts.h"
+
+#include <getopt.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "error.h"
+
+uint8_t getoptions(int32_t argc, char* const* argv, int32_t* ncpus) {
+	uint8_t opts = 0;
+	char opt;
+
+	char const* const msg = "-%c has already been set";
+	while ((opt = getopt(argc, argv, "lavi")) != -1) {
+		switch (opt) {
+		case 'l':
+			if (opts & OPT_LIST_CORES) fatal(msg, 'l');
+			opts |= OPT_LIST_CORES;
+			break;
+		case 'a':
+			if (opts & OPT_SET_ALL) fatal(msg, 'a');
+			opts |= OPT_SET_ALL;
+			break;
+		case 'v':
+			if (opts & OPT_VERBOSE) fatal(msg, 'v');
+			opts |= OPT_VERBOSE;
+			break;
+		case 'i':
+			if (opts & OPT_INVERT) fatal(msg, 'i');
+			opts |= OPT_INVERT;
+			break;
+		case '?':
+			fatal("usage: %s [number] [-l] [-a] [-v] [-i]", argv[0]);
+		}
+	}
+
+	if (optind < argc) {
+		char* num = argv[optind];
+		*ncpus = atoi(num);
+	} else fatal("you must provide a number!");
+
+	return opts;
+}
diff --git a/src/opts.h b/src/opts.h
new file mode 100644
index 0000000..9daf00a
--- /dev/null
+++ b/src/opts.h
@@ -0,0 +1,11 @@
+#pragma once
+#include <stdint.h>
+
+enum opt {
+	OPT_LIST_CORES = 1, // option that lists the total amount of cores that are set
+	OPT_SET_ALL = 2,    // option to set all cores, regardless of their assumed state
+	OPT_VERBOSE = 4,    // print which cores are disabled/enabled
+	OPT_INVERT = 8,     // 'num' now represents the amount of cores to disable
+};
+
+uint8_t getoptions(int32_t, char* const*, int32_t*);