diff --git a/README.md b/README.md
index 99bb4ec..799873f 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,7 @@ We propose to use a compact C portable library. Compatibility with an Oled displ
 
 It is admittedly very convenient to just use Serial.print(var); since it doesn't require you to specify the type of variable. Though when trying for example to output data in tabular style the processor needs to know the data type used so that it can reserve the adequate space for it in its output. It might seem like a big inconvenience to specify the data type with any statement that outputs data over serial but then again for debugging purposes it makes perfectly sense in terms of speed AND size of the resulting code. By the same reasons we also do not use a buffer as it is needed only in specific situations.
 
-## Example comparison between Didel TerSer and Arduino Serial
+### Example comparison between Didel TerSer and Arduino Serial
 | TerSer | Output TerSer | Output Serial | Arduino Serial |
 | ------------- | ------------- | ------------- | ------------- |
 | Car('Z'); | Z | Z | Serial.print('Z'); |
@@ -29,6 +29,8 @@ It is admittedly very convenient to just use Serial.print(var); since it doesn't
 
 *uint16_t  v16=1120; uint16_t  v16b=20;  int16_t  v16s=20;*
 
+### Using tabular data
+
 Filling the non significative digits with zero or space is a general options, named ShowZ(); and HideZ(); 
 
 The Tab(nn); function, allows to align data of different types.
@@ -43,3 +45,48 @@ HideZ();Dec8s(3);    SetTab(15);
 
 It is up to you to add functions like TextNL();
 if you need to keep your Serial.println() habits.
+
+### TerSer Limitations
+TerSer does not print floating point numbers. 
+The may happen some day with one more file to import, e.g. names TerFloat.h.
+
+Dec8(); and Dec16(); use a tricky macro to recognize the signed or unsigned data type. The parameter must be a single variable, e.g. Dec8(var); Dec8(var+2); will give wrong results.
+Code will be shorter and there will be no limitation if you use Dec8u(any unsigned expr); and 
+Dec8s(any signed expr);, same of course Dec16u(); and Dec16s();
+
+### Code size and timing comparison
+Code size has been obtained by calling one function at a time, compiler under the usual -0s mode. Size is the difference with the empty file size. TerSer.h can of course be used with setup() and loop(). It add the ~300 bytes Arduino initializations.
+Execution time has been measured with a Nop replacing the SendCar function. The time depends on the baud rate, ~1 ms per character displayed at 9600 bits/s.
+
+| //TerSer.ino  Terminal série 174b 0v
+#include "TerSer.h"
+int main() {
+  SetupTerSer();
+
+while(1) {     add 174b for total size 
+//  Text("Test"); // 20b 
+//  Bin8(v8);     // 16b  3us
+//  Bin16(v16);   // 42b  6,8us
+//  Hex8(v8);     // 52b  4us
+//  Hex16(v16);   // 82b 11.5us
+//  Dec8(vs8);    //116b 13us
+//  Dec16(vs16);  //200b 52us 14v
+                  // max 14 variables
+
+} // end while(1)
+} // end main() | // PrintArdui vide 1426b  184v
+void setup() {
+ Serial.begin(9600);
+}
+void loop() {  add 1426b for program size
+// Serial.print("Text");   //  22 190v
+// Serial.println("text"); //  40 192v
+// Serial.print(123,HEX);  //  60 184v 
+// Serial.print(12335,HEX);// 120 184v 
+// Serial.print(-123);     // 266 184v 
+// Serial.print(-12345);   // 266 184v
+// Serial.println(12345);  // 286 188v
+
+for(;;);
+} |
+