diff --git a/code128/encode.go b/code128/encode.go
index 6c6a927..ff81fc5 100644
--- a/code128/encode.go
+++ b/code128/encode.go
@@ -43,7 +43,11 @@ func getCodeIndexList(content []rune) *utils.BitList {
 
 		if shouldUseCTable(content[i:], curEncoding) {
 			if curEncoding != startCSymbol {
-				result.AddByte(startCSymbol)
+				if curEncoding == byte(0) {
+					result.AddByte(startCSymbol)
+				} else {
+					result.AddByte(codeCSymbol)
+				}
 				curEncoding = startCSymbol
 			}
 			idx := (content[i] - '0') * 10
@@ -53,24 +57,45 @@ func getCodeIndexList(content []rune) *utils.BitList {
 			result.AddByte(byte(idx))
 		} else {
 			if curEncoding != startBSymbol {
-				result.AddByte(startBSymbol)
+				if curEncoding == byte(0) {
+					result.AddByte(startBSymbol)
+				} else {
+					result.AddByte(codeBSymbol)
+				}
 				curEncoding = startBSymbol
 			}
-			idx := strings.IndexRune(bTable, content[i])
+			var idx int
+			switch content[i] {
+			case FNC1:
+				idx = 102
+				break
+			case FNC2:
+				idx = 97
+				break
+			case FNC3:
+				idx = 96
+				break
+			case FNC4:
+				idx = 100
+				break
+			default:
+				idx = strings.IndexRune(bTable, content[i])
+				break
+			}
+
 			if idx < 0 {
 				return nil
 			}
 			result.AddByte(byte(idx))
 		}
 	}
-	fmt.Println(result.GetBytes())
 	return result
 }
 
 // Encode creates a Code 128 barcode for the given content
 func Encode(content string) (barcode.Barcode, error) {
 	contentRunes := strToRunes(content)
-	if len(contentRunes) < 0 || len(contentRunes) > 80 {
+	if len(contentRunes) <= 0 || len(contentRunes) > 80 {
 		return nil, fmt.Errorf("content length should be between 1 and 80 runes but got %d", len(contentRunes))
 	}
 	idxList := getCodeIndexList(contentRunes)
diff --git a/code128/encode_test.go b/code128/encode_test.go
new file mode 100644
index 0000000..a0e2a83
--- /dev/null
+++ b/code128/encode_test.go
@@ -0,0 +1,51 @@
+package code128
+
+import (
+	"image/color"
+	"testing"
+)
+
+func testEncode(t *testing.T, txt, testResult string) {
+	code, err := Encode(txt)
+	if err != nil || code == nil {
+		t.Error(err)
+	} else {
+		if code.Bounds().Max.X != len(testResult) {
+			t.Errorf("%v: length missmatch", txt)
+		} else {
+			for i, r := range testResult {
+				if (code.At(i, 0) == color.Black) != (r == '1') {
+					t.Errorf("%v: code missmatch on position %d", txt, i)
+				}
+			}
+		}
+	}
+}
+
+func Test_EncodeFunctionChars(t *testing.T) {
+	encFNC1 := "11110101110"
+	encFNC2 := "11110101000"
+	encFNC3 := "10111100010"
+	encFNC4 := "10111101110"
+	encStartB := "11010010000"
+	encStop := "1100011101011"
+
+	testEncode(t, string(FNC1)+"123", encStartB+encFNC1+"10011100110"+"11001110010"+"11001011100"+"11001000010"+encStop)
+	testEncode(t, string(FNC2)+"123", encStartB+encFNC2+"10011100110"+"11001110010"+"11001011100"+"11100010110"+encStop)
+	testEncode(t, string(FNC3)+"123", encStartB+encFNC3+"10011100110"+"11001110010"+"11001011100"+"11101000110"+encStop)
+	testEncode(t, string(FNC4)+"123", encStartB+encFNC4+"10011100110"+"11001110010"+"11001011100"+"11100011010"+encStop)
+}
+
+func Test_Unencodable(t *testing.T) {
+	if _, err := Encode(""); err == nil {
+		t.Fail()
+	}
+	if _, err := Encode("ä"); err == nil {
+		t.Fail()
+	}
+}
+
+func Test_EncodeCTable(t *testing.T) {
+	testEncode(t, "HI345678H", "110100100001100010100011000100010101110111101000101100011100010110110000101001011110111011000101000111011000101100011101011")
+	testEncode(t, "334455", "11010011100101000110001000110111011101000110100100111101100011101011")
+}
diff --git a/code128/encodingtable.go b/code128/encodingtable.go
index a102821..a32b31c 100644
--- a/code128/encodingtable.go
+++ b/code128/encodingtable.go
@@ -1,6 +1,6 @@
 package code128
 
-var encodingTable [107][]bool = [107][]bool{
+var encodingTable = [107][]bool{
 	[]bool{true, true, false, true, true, false, false, true, true, false, false},
 	[]bool{true, true, false, false, true, true, false, true, true, false, false},
 	[]bool{true, true, false, false, true, true, false, false, true, true, false},
@@ -110,9 +110,24 @@ var encodingTable [107][]bool = [107][]bool{
 	[]bool{true, true, false, false, false, true, true, true, false, true, false, true, true},
 }
 
-const startASymbol byte = 103
+// const startASymbol byte = 103
 const startBSymbol byte = 104
 const startCSymbol byte = 105
+
+const codeBSymbol byte = 100
+const codeCSymbol byte = 99
+
 const stopSymbol byte = 106
 
+const (
+	// FNC1 - Special Function 1
+	FNC1 = '\u00f1'
+	// FNC2 - Special Function 2
+	FNC2 = '\u00f2'
+	// FNC3 - Special Function 3
+	FNC3 = '\u00f3'
+	// FNC4 - Special Function 4
+	FNC4 = '\u00f4'
+)
+
 const bTable = " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~"