diff --git a/lang/bytecode.c b/lang/bytecode.c
index 7531b10..cb4ebe7 100644
--- a/lang/bytecode.c
+++ b/lang/bytecode.c
@@ -7,15 +7,19 @@
 #include "object.h"
 #include "vm.h"
 
+// Opcode definitions, see bytecode_run for further documentation
 enum opcodes {
+	// 0x00 is reserved for inline strings
 	OP_NUM = 0x01,
 	OP_RET = 0x03,
+	// 0x02 was an earlier variant of OP_DROP
 	OP_CALL = 0x04,
 	OP_NULL = 0x05,
 	OP_GET = 0x06,
 	OP_SET = 0x07,
 	OP_DROP = 0x08,
 	OP_DEPTH_CHECK = 0x09,
+	// 0x60 onwards are reserved for inline strings
 };
 
 // clang-format off
@@ -34,6 +38,8 @@
 	unsigned char op = OP_RET;
 	while ((op = *pos_code++) != OP_RET) {
 		switch (op) {
+		// OP_NUM pushes a number on to the stack
+		// First argument is a 4-byte little endian number
 		case OP_NUM: {
 			int num = 0;
 			num |= *pos_code++ << 0;
@@ -43,6 +49,9 @@
 			vm_stack_push(state, number_create(num));
 			break;
 		}
+		// OP_CALL dispatches a call to the top of stack object
+		// First argument is a 1-byte argument count
+		// Second argument is the call string
 		case OP_CALL: {
 			int arg_count = *pos_code++;
 			const char *dispatch = (const char *)pos_code;
@@ -51,32 +60,43 @@
 			object_drop(&obj);
 			break;
 		}
+		// OP_NULL pushes object_none on to the stack
 		case OP_NULL: {
 			vm_stack_push(state, object_none());
 			break;
 		}
+		// OP_GET duplicates an element from the stack and stores
+		// the result at the top
+		// First argument is the stack index
 		case OP_GET: {
 			Object obj = vm_stack_get(state, *pos_code++);
 			vm_stack_push(state, obj);
 			break;
 		}
+		// OP_SET stores the stack top element at a stack index
+		// The stack top element is dropped in the process
+		// First argument is the stack index
 		case OP_SET: {
 			Object obj = vm_stack_pop(state);
 			vm_stack_set(state, *pos_code++, obj);
 			break;
 		}
+		// OP_DROP drops multiple stack elements starting at the top
+		// First argument is the number of elements to drop
 		case OP_DROP: {
 			vm_stack_drop(state, *pos_code++);
 			break;
 		}
+		// OP_DEPTH_CHECK checks that the stack is a certain size
+		// First argument is the expected depth
 		case OP_DEPTH_CHECK: {
 			int depth = *pos_code++;
 			abort_if(vm_stack_depth(state) != depth,
 				"stack depth mismatch");
 			break;
 		}
+		// Skip over strings and unknown OPs
 		default:
-			// Skip over ASCII and unknown OPs
 			break;
 		}
 	}