Not the cleanest way to do this but added in keyword detection.

scanner.c

@@ -4,6 +4,30 @@
 #include <string.h>
 #include <ctype.h>
 
+typedef struct {
+    char* keyword;
+    TokenType type;
+} KeywordPair;
+
+KeywordPair keywords[KEYWORD_COUNT] = {
+    { "and", AND },
+    { "class", CLASS },
+    { "else", ELSE },
+    { "false", FALSE },
+    { "for", FOR },
+    { "fun", FUN },
+    { "if", IF },
+    { "nil", NIL },
+    { "or", OR },
+    { "print", PRINT },
+    { "return", RETURN },
+    { "super", SUPER },
+    { "this", THIS },
+    { "true", TRUE },
+    { "var", VAR },
+    { "while", WHILE }
+};
+
 const char* source_code;
 //Start and Current hold the offsets that index into the string source_code.
 int start;   //Points to the first character in the lexeme being scanned.
@@ -23,6 +47,7 @@ void ParseString(TokenList *);
 void ParseNumber(TokenList *);
 void ParseIdentifier(TokenList *);
 int IsAlpha(char c);
+KeywordPair* Get(char*);
 
 TokenList* ScanTokens(const char* source) {
     if (!source) return NULL;
@@ -255,11 +280,29 @@ char PeekNext() {
 void ParseIdentifier(TokenList * list) {
     while(IsAlpha(Peek())) Advance();
 
-    AddTokenToList(Identifier, &source_code[start], current - start, list);
+    char* lexeme = calloc(sizeof(char*), (current - start + 1));
+    
+    snprintf(lexeme, current - start + 1, "%s", &source_code[start]);
+
+    KeywordPair* result = Get(lexeme);
+
+    if (result) AddTokenToList(result->type, &source_code[start], current - start, list);
+    else AddTokenToList(Identifier, &source_code[start], current - start, list);
+
+    free(lexeme);
 }
 
 int IsAlpha(char c) {
     return  (c >= 'a' && c <= 'z') ||
             (c >= 'A' && c <= 'Z') ||
             (c == '_');
+}
+
+KeywordPair* Get(char* text) {
+    if (!text) return NULL;
+
+    for (int i = 0; i < KEYWORD_COUNT; i++) 
+        if (strcmp(text, keywords[i].keyword) == 0) return &keywords[i];
+
+    return NULL;
 }

scanner.h

@@ -2,6 +2,7 @@
 #define SCANNER_H
 
 #define DEFAULT_TOKENLIST_SIZE 32
+#define KEYWORD_COUNT 16
 
 typedef enum {
     //Single-character tokens