diff --git a/src/assemble.c b/src/assemble.c
index e2ad1c8..ae760c0 100755
--- a/src/assemble.c
+++ b/src/assemble.c
@@ -1,5 +1,7 @@
 #include <stdlib.h>
+#include <stdio.h>
 
 int main(int argc, char **argv) {
+  
   return EXIT_SUCCESS;
 }
diff --git a/src/fileaccess.c b/src/fileio.c
similarity index 96%
rename from src/fileaccess.c
rename to src/fileio.c
index 14bf70d..45b25e8 100644
--- a/src/fileaccess.c
+++ b/src/fileio.c
@@ -37,6 +37,7 @@ int writeBinaryFile(word instrs[], char outputFile[]){
 
 //reads assembly file of "inputFile" name, and passes 
 //each line into a parser
+//TODO: allocate whole file in memory, line-by-line
 int readAssemblyFile(char inputFile[]) {
     if (!isValidFileFormat(filename, "s")){
         exit(EXIT_FAILURE);
diff --git a/src/parser.c b/src/parser.c
index 15f010a..53b8e0c 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -59,10 +59,10 @@ char *tokeniseOperands(char* str, int operandCount, char *operands[]){
         operand = strtok(NULL, OPERAND_DELIMITER);
         operands[operandCount] = operand;
     }
-    return(operands);
-
 }
 
+//takes inputted assembly line and returns a 
+//pointer to an abstract representation of the instruction
 a64inst_instruction *parser(char asmLine[]){
     a64inst_instruction *instr = malloc(sizeof(a64inst_instruction)); 
     if (instr == NULL){
@@ -80,6 +80,7 @@ a64inst_instruction *parser(char asmLine[]){
     }
 
     //"opcode operand1, {operand2}, ..."
+    //duplicated as strtok modifies the input string
     char *stringptr = strdup(asmLine);
 
     char *opcode = strtok(stringptr, " ");
diff --git a/src/symboltable.c b/src/symboltable.c
new file mode 100644
index 0000000..fb448c1
--- /dev/null
+++ b/src/symboltable.c
@@ -0,0 +1,43 @@
+#include <stdio.h>
+
+typedef struct st st;
+
+
+
+typedef struct {
+    const void* key;
+    void* value;
+    node* prev;
+    node* next;
+} node;
+
+struct st {
+    node* head;
+    node* tail;
+};
+
+// add new node to the end
+void st_add(st table, void* key, void* value) {
+    node n = {key, value, table.tail};
+    (*(table.tail)).next = &n;
+    table.tail = &n;
+}
+
+// returns the pointer to key of the specified node, or null, if it does not exist
+void* st_search(st table, void* key) {
+    return nodeSearch(table.head, key);
+}
+
+void* nodeSearch(node* n, void* key) {
+    if (n != NULL) {
+        if ((*n).key == key) {
+            return (*n).value;
+        }
+        else {
+            return nodeSearch((*n).next, key);
+        }
+    }
+    else {
+        return NULL;
+    }
+}
\ No newline at end of file