diff --git a/internal/commands/byte_test.go b/internal/commands/byte_test.go
index 16874fd..183a6d8 100644
--- a/internal/commands/byte_test.go
+++ b/internal/commands/byte_test.go
@@ -205,7 +205,7 @@ func TestByteCommand_Interpret(t *testing.T) {
 		},
 		{
 			name:    "byte with binary",
-			text:    "BYTE x = !11111111",
+			text:    "BYTE x = %11111111",
 			wantErr: false,
 			checkVar: func(t *testing.T, ctx *compiler.CompilerContext) {
 				sym := ctx.SymbolTable.Lookup("x", nil)
diff --git a/internal/commands/word_test.go b/internal/commands/word_test.go
index 233ea88..6df3b18 100644
--- a/internal/commands/word_test.go
+++ b/internal/commands/word_test.go
@@ -227,7 +227,7 @@ func TestWordCommand_Interpret(t *testing.T) {
 		},
 		{
 			name:    "word with binary",
-			text:    "WORD x = !1111111111111111",
+			text:    "WORD x = %1111111111111111",
 			wantErr: false,
 			checkVar: func(t *testing.T, ctx *compiler.CompilerContext) {
 				sym := ctx.SymbolTable.Lookup("x", nil)
diff --git a/internal/utils/utils.go b/internal/utils/utils.go
index 8788bb1..755d168 100644
--- a/internal/utils/utils.go
+++ b/internal/utils/utils.go
@@ -232,8 +232,8 @@ func evaluateTerm(term string, lookup ConstantLookup) (int64, error) {
 		return val, nil
 	}
 
-	// Check for binary: !11111111
-	if strings.HasPrefix(term, "!") {
+	// Check for binary: %11111111
+	if strings.HasPrefix(term, "%") {
 		val, err := strconv.ParseInt(term[1:], 2, 64)
 		if err != nil {
 			return 0, fmt.Errorf("invalid binary number: %w", err)
diff --git a/internal/utils/utils_test.go b/internal/utils/utils_test.go
index 802d4ab..bc1ebcc 100644
--- a/internal/utils/utils_test.go
+++ b/internal/utils/utils_test.go
@@ -204,14 +204,14 @@ func TestEvaluateExpression(t *testing.T) {
 		{name: "hex word", expr: "$C000", want: 0xC000},
 
 		// Binary
-		{name: "binary 8bit", expr: "!11111111", want: 255},
-		{name: "binary zero", expr: "!00000000", want: 0},
-		{name: "binary mixed", expr: "!10101010", want: 0xAA},
+		{name: "binary 8bit", expr: "%11111111", want: 255},
+		{name: "binary zero", expr: "%00000000", want: 0},
+		{name: "binary mixed", expr: "%10101010", want: 0xAA},
 
 		// Addition
 		{name: "add decimal", expr: "10+20", want: 30},
 		{name: "add hex", expr: "$10+$20", want: 0x30},
-		{name: "add binary", expr: "!1010+!0101", want: 15},
+		{name: "add binary", expr: "%1010+%0101", want: 15},
 		{name: "add multiple", expr: "10+20+30", want: 60},
 
 		// Subtraction