diff --git a/LibAutomaton/CellElement.h b/LibAutomaton/CellElement.h
index d9557ce..60b27e9 100644
--- a/LibAutomaton/CellElement.h
+++ b/LibAutomaton/CellElement.h
@@ -9,7 +9,8 @@
 typedef enum Bool{
 
 	true  = 1,
-	false = 0
+	false = 0,
+	ERROR = -1
 
 } bool;
 
diff --git a/LibAutomaton/matrix.c b/LibAutomaton/matrix.c
index 6896a18..6a584aa 100644
--- a/LibAutomaton/matrix.c
+++ b/LibAutomaton/matrix.c
@@ -30,13 +30,21 @@ Matrix CreateMatrix(){
 	return matrix;
 }
 
-void CreateMatrixElem(Matrix matrix, int ColPos, int RowPos){
+void SetMatrixDim(Matrix matrix,int nbCols,int nbRows){
+	matrix.colCount = nbCols;
+	matrix.rowCount = nbRows;
+}
+
+bool CreateMatrixElem(Matrix matrix, int ColPos, int RowPos){
 	ListElement * Row = NULL;
 	ListElement * Col = NULL;
 	int error = 0;
 	cellElement * elem = NULL;
 	cellElement * tmp = NULL;
 
+	if (matrix.colCount < ColPos || matrix.rowCount < RowPos){
+		return ERROR;
+	}
 	elem = CreateCellElem();
 	SetPositionIndex(elem,ColPos,RowPos);
 
@@ -95,7 +103,11 @@ void CreateMatrixElem(Matrix matrix, int ColPos, int RowPos){
 
 	if (error != 0){
 		free(elem);
+		return true;
+	}else{
+		return false;
 	}
+
 }
 
 cellElement * FindMatrixElem(Matrix matrix, int ColPos, int RowPos){
@@ -186,21 +198,28 @@ int SupprMatrixElem(Matrix matrix, int ColPos, int RowPos){
 }
 
 bool GetCellValue(Matrix matrix, int ColPos, int RowPos){
+	if (matrix.colCount < ColPos || matrix.rowCount < RowPos){
+		return ERROR;
+	}
+
 	if (FindMatrixElem(matrix,ColPos,RowPos) == NULL){
 		return false;
 	}
 	return true;
 }
 
-void SetCellValue(Matrix matrix, int ColPos, int RowPos,bool value){
+bool SetCellValue(Matrix matrix, int ColPos, int RowPos,bool value){
 	if (value == true){
-		CreateMatrixElem(matrix,ColPos,RowPos);
+		return CreateMatrixElem(matrix,ColPos,RowPos);
 	}else{
-		SupprMatrixElem(matrix,ColPos,RowPos);
+		if ( SupprMatrixElem(matrix,ColPos,RowPos) >= 0 ){
+			return true;
+		}else{
+			return false;
+		}
 	}
 
 }
 /* todos:
-*gerer bornes matrice
 *print matrice
 */
\ No newline at end of file
diff --git a/LibAutomaton/matrix.h b/LibAutomaton/matrix.h
index 1916bce..bfdd828 100644
--- a/LibAutomaton/matrix.h
+++ b/LibAutomaton/matrix.h
@@ -67,12 +67,15 @@ cellElement * FindMatrixElem(Matrix matrix, int ColPos, int RowPos);
 *@return void
 *
 */
-void CreateMatrixElem(Matrix matrix, int ColPos, int RowPos);
+bool CreateMatrixElem(Matrix matrix, int ColPos, int RowPos);
 
 int SupprMatrixElem(Matrix matrix, int ColPos, int RowPos);
 
-void SetCellValue(Matrix matrix, int ColPos, int RowPos,bool value);
+bool SetCellValue(Matrix matrix, int ColPos, int RowPos, bool value);
 
 bool GetCellValue(Matrix matrix, int ColPos, int RowPos);
+
+void SetMatrixDim(Matrix matrix,int nbCols,int nbRows);
+
 #endif