diff --git a/src/main/antlr/VSLParser.g b/src/main/antlr/VSLParser.g
index 46b5068..b8c7b69 100644
--- a/src/main/antlr/VSLParser.g
+++ b/src/main/antlr/VSLParser.g
@@ -22,11 +22,37 @@ options {
 }
 
 program returns [ProgramImp p] :
+  pro=prototypes
   func=functions
   EOF
-  {$p = new ProgramImp($func.out);}
+  {$p = new ProgramImp($func.out,$pro.out);}
 ;
 
+prototypes returns [ArrayList<Prototype> out]
+  @init{
+    $out = new ArrayList<Prototype>();
+  }:
+    (proto {
+      $out.add($proto.out);
+    })*
+  ;
+
+proto returns [Prototype out]:
+  PROTOTYPE t=type i=ident ParO v=vars_locaux ParF
+    {
+      $out=new PrototypeImp($t.return_type,$i.out, $v.out);
+    }
+  ; 
+
+vars_locaux returns [ArrayList<String> out]
+  @init{
+    $out = new ArrayList<String>();
+  }: 
+    (
+      (ii1=ident {$out.add($ii1.out);})
+      (VIRGULE ii2=ident  {$out.add($ii2.out);})*
+    )*
+  ; 
 
 functions returns [ArrayList<Function> out]
   @init{
diff --git a/src/main/java/TP2/Error/TypeCheckExprDiag.java b/src/main/java/TP2/Error/TypeCheckExprDiag.java
new file mode 100644
index 0000000..2625026
--- /dev/null
+++ b/src/main/java/TP2/Error/TypeCheckExprDiag.java
@@ -0,0 +1,34 @@
+package TP2.Error;
+import TP2.asd.Interface.*;
+public class TypeCheckExprDiag {
+    private Type t;
+    private String err;
+    private boolean check;
+
+    public TypeCheckExprDiag(Type type) {
+        this.t = type;
+        this.check = true;
+        this.err = null;
+    }
+
+    public TypeCheckExprDiag(String error){
+        this.err=error;
+        this.check=false;
+    }
+
+    public boolean get_check(){
+        return this.check;
+    }
+    
+    public Type get_type(){
+        return this.t;
+    }
+    
+    public static TypeCheckExprDiag error(String err){
+        return new TypeCheckExprDiag(err);
+    }
+
+    public static TypeCheckExprDiag checked(Type type){
+        return new TypeCheckExprDiag(type);
+    }
+}
diff --git a/src/main/java/TP2/Error/TypeChecking.java b/src/main/java/TP2/Error/TypeChecking.java
index a70f201..13ee354 100644
--- a/src/main/java/TP2/Error/TypeChecking.java
+++ b/src/main/java/TP2/Error/TypeChecking.java
@@ -1,34 +1,155 @@
 package TP2.Error;
 
 import TP2.asd.SymTable;
-import TP2.asd.Interface.ExprVisitor;
-import TP2.asd.Program.BinopExpressionImp;
-import TP2.asd.Program.ConstImp;
-import TP2.asd.Program.VarImp;
+import TP2.asd.Program.*;
+import TP2.asd.Interface.*;
 
 public class TypeChecking {
-    private SymTable st;
 
-    /*
-    public class TypeCheckExpr implements ExprVisitor<SymTable ,TypeCheckExprDiag>{
+    public class TypeCheckProg implements ProgramVisitor<SymTable, TypeCheckExprDiag>{
+        private TypeCheckFunction func_check;
+        @Override
+        public TypeCheckExprDiag visitProgram(ProgramImp prog, SymTable h) {
+            SymTable st= new SymTable();
+            for (Function f : prog.fonctions()) {
+                TypeCheckExprDiag diag = f.accept(func_check, h);
+                if (!diag.get_check()) return diag;
+            }
+            return TypeCheckExprDiag.checked(null);
+        }
+    }
+
+    public class TypeCheckFunction implements FunctionVisitor<SymTable, TypeCheckExprDiag>{
+        private TypeCheckInstr instr_check;
+        @Override
+        public TypeCheckExprDiag visitFunction(FunctionImp f, SymTable h) {
+           return f.instruction().accept(instr_check,h);
+        }
+    }
+
+    public class TypeCheckInstr implements InstrVisitor<SymTable, TypeCheckExprDiag> {
+        private TypeCheckExpr expr_check; 
+        @Override
+        public TypeCheckExprDiag visitReturn(Return_instrImp instr, SymTable h) {
+            return instr.e().accept(expr_check, h);
+        }
 
         @Override
-        public TypeCheckExprDiag visitConst(ConstImp e, SymTable h) {
+        public TypeCheckExprDiag visitBloc(BlocImp instr, SymTable h) {
+            for(Instruction i: instr.instrs()){
+                TypeCheckExprDiag diag= i.accept(this, h);
+                if(!diag.get_check()) return diag;
+            }
+            return TypeCheckExprDiag.checked(null);
+        }
+
+        @Override
+        public TypeCheckExprDiag visitBlocDec(BlocDecImp instr, SymTable h) {
             // TODO Auto-generated method stub
-            throw new UnsupportedOperationException("Unimplemented method 'visitConst'");
+            throw new UnsupportedOperationException("Unimplemented method 'visitBlocDec'");
+        }
+
+        @Override
+        public TypeCheckExprDiag visitAssign(AssignImp instr, SymTable h) {
+            if(!h.searchVar(instr.t())){
+                return TypeCheckExprDiag.error("Variable "+instr.t()+" n'existe pas");
+            }
+            Type t_type=h.getvar_Type(instr.t()).type;
+            TypeCheckExprDiag expr= instr.e().accept(expr_check, h);
+
+            if (!expr.get_check()) return expr;
+            //Verify type t = Type expr
+            if(!t_type.getClass().equals(expr.get_type().getClass())){
+                return TypeCheckExprDiag.error("Type d'expression est different que le type de variable");
+            }
+            return TypeCheckExprDiag.checked(t_type);
+        }
+
+        @Override
+        public TypeCheckExprDiag visitPrint(PrintImp instr, SymTable h) {
+           for(Object o :instr.t()){
+            //We have string and expression
+            if(o instanceof Expression e){
+                TypeCheckExprDiag result = e.accept(expr_check, h);
+                if (!result.get_check()) return result;
+            }
+           }
+           return TypeCheckExprDiag.checked(null);
+        }
+
+        @Override
+        public TypeCheckExprDiag visitRead(ReadImp instr, SymTable h) {
+            for(VarImp v: instr.t()){
+                if(!h.searchVar(v.name())){
+                    return TypeCheckExprDiag.error("Variable "+v.name()+" n'existe pas");
+                }
+            }
+            return TypeCheckExprDiag.checked(null);
+        }
+
+        @Override
+        public TypeCheckExprDiag visitIfThen(IfThenImp instr, SymTable h) {
+            TypeCheckExprDiag cond =instr.e().accept(expr_check, h);
+            if(!cond.get_check()) return cond;
+            if (!(cond.get_type() instanceof Type_intImp)){
+                return TypeCheckExprDiag.error("Condition n'est pas un int");
+            }
+            return instr.i1().accept(this, h);
+        }
+
+        @Override
+        public TypeCheckExprDiag visitIfThenElse(IfThenElseImp instr, SymTable h) {
+            TypeCheckExprDiag cond =instr.e().accept(expr_check, h);
+            if(!cond.get_check()) return cond;
+            if (!(cond.get_type() instanceof Type_intImp)){
+                return TypeCheckExprDiag.error("Condition n'est pas un int");
+            }
+            
+            TypeCheckExprDiag then= instr.i1().accept(this, h);
+            if (!then.get_check()) return then;
+            return instr.i2().accept(this, h);
+        }
+
+        @Override
+        public TypeCheckExprDiag visitWhile(WhileImp instr, SymTable h) {
+            TypeCheckExprDiag cond =instr.e().accept(expr_check, h);
+            if(!cond.get_check()) return cond;
+            if (!(cond.get_type() instanceof Type_intImp)){
+                return TypeCheckExprDiag.error("Condition n'est pas un int");
+            }
+            return instr.i1().accept(this, h);
+        } 
+    }
+
+    public class TypeCheckExpr implements ExprVisitor<SymTable ,TypeCheckExprDiag>{
+        @Override
+        public TypeCheckExprDiag visitConst(ConstImp e, SymTable h) {
+            return TypeCheckExprDiag.checked(new Type_intImp());
         }
 
         @Override
         public TypeCheckExprDiag visitVar(VarImp e, SymTable h) {
-            // TODO Auto-generated method stub
-            throw new UnsupportedOperationException("Unimplemented method 'visitVar'");
+            if(!h.searchVar(e.name())){
+                return TypeCheckExprDiag.error("Ce variable n'existe pas");
+            }
+            Type e_type= h.getvar_Type(e.name()).type;
+            return TypeCheckExprDiag.checked(e_type);
         }
 
         @Override
         public TypeCheckExprDiag visitBinOp(BinopExpressionImp e, SymTable h) {
-            TypeCheckExprDiag tce1 = e.e1().accept(this, h) ;
-            TypeCheckExprDiag tce2 = e.e2().accept(this, h) ;
+            TypeCheckExprDiag tce1 = e.e1().accept(this, h);
+            TypeCheckExprDiag tce2 = e.e2().accept(this, h);
+            
+            // Check if not ok then return its error
+            if(!tce1.get_check()) return tce1;
+            if(!tce2.get_check()) return tce2;
+
+            // Check int + int
+            if (!(tce1.get_type() instanceof Type_intImp) || !(tce2.get_type() instanceof Type_intImp) ){
+                return TypeCheckExprDiag.error("Ses types sont different");
+            }
+            return TypeCheckExprDiag.checked(tce1.get_type());
         }
     }
-     */
 }
diff --git a/src/main/java/TP2/asd/Interface.java b/src/main/java/TP2/asd/Interface.java
index 56a2da8..3e1f290 100644
--- a/src/main/java/TP2/asd/Interface.java
+++ b/src/main/java/TP2/asd/Interface.java
@@ -14,7 +14,15 @@ public interface Interface{
     public interface ProgramVisitor<H,S> {
         public S visitProgram(ProgramImp prog, H h);
     }
+    
+    //PROTOTYPE
+    public interface Prototype{
+        public <H,S> S accept(PrototypeVisitor<H,S> v, H h);
+    }
 
+    public interface PrototypeVisitor<H,S> {
+        public S visitPrototype(PrototypeImp proto, H h);
+    }
 
     //FUNCTION
     public interface Function {
diff --git a/src/main/java/TP2/asd/PrettyprinterVisitor.java b/src/main/java/TP2/asd/PrettyprinterVisitor.java
index 8492169..026517a 100644
--- a/src/main/java/TP2/asd/PrettyprinterVisitor.java
+++ b/src/main/java/TP2/asd/PrettyprinterVisitor.java
@@ -4,6 +4,7 @@ import TP2.asd.Interface.*;
 import TP2.asd.Program.*;
 
 public class PrettyprinterVisitor implements    ProgramVisitor<String,String>,
+                                                PrototypeVisitor<String,String>,
                                                 FunctionVisitor<String,String>,
                                                 DeclVisitor<String,String>,
                                                 InstrVisitor<String,String>,
@@ -18,6 +19,11 @@ public class PrettyprinterVisitor implements    ProgramVisitor<String,String>,
     @Override
     public String visitProgram(ProgramImp prog, String indent) {
         String str ="";
+            for(int i= 0; i<prog.protos().size();i++){
+                str+=prog.protos().get(i).accept(this, INDENT);
+                if(i<prog.protos().size()-1) str += "\n";
+            }
+            str+="\n";
             for(int i = 0; i<prog.fonctions().size(); i++){
                 str += prog.fonctions().get(i).accept(this,INDENT);
                 if(i<prog.fonctions().size()-1) str += "\n";
@@ -25,8 +31,20 @@ public class PrettyprinterVisitor implements    ProgramVisitor<String,String>,
         return str;
     }
 
-    //FUNCTION
+    //PROTOTYPE
+    @Override
+    public String visitPrototype(PrototypeImp proto, String indent){
+        String str= indent + "PROTO "+proto.type().accept(this, "")+ " "+ proto.nom() + "(";
+        for(int i=0; i<proto.s().size();i++){
+            str+=proto.s().get(i);
+            if((i<proto.s().size()-1)){
+                str+=", ";
+            }
+        }
+        return str+")";
+    }
 
+    //FUNCTION
     @Override
     public String visitFunction(FunctionImp fun, String indent) {
         String str = indent+"FUNC " + fun.type().accept(this,"")+ " " + fun.nom() +"() ";
@@ -35,7 +53,6 @@ public class PrettyprinterVisitor implements    ProgramVisitor<String,String>,
     }
 
     //DELCARATION
-
     @Override
     public String visitDeclaration(DeclarationImp instr, String indent) {
         String str = indent +instr.t().accept(this,"") + " ";
@@ -47,7 +64,6 @@ public class PrettyprinterVisitor implements    ProgramVisitor<String,String>,
     }
 
     //INSTRUCTION 
-
     @Override
     public String visitReturn(Return_instrImp instr, String indent) {
         return indent+"RETURN " + instr.e().accept(this,"");
diff --git a/src/main/java/TP2/asd/Program.java b/src/main/java/TP2/asd/Program.java
index ebaaf99..77cb794 100644
--- a/src/main/java/TP2/asd/Program.java
+++ b/src/main/java/TP2/asd/Program.java
@@ -7,7 +7,7 @@ import TP2.llvm.ProgramLLVM.*;
 public class Program{
 
     //Prog
-    public static record ProgramImp(ArrayList<Function> fonctions) implements ProgramI{
+    public static record ProgramImp(ArrayList<Function> fonctions,ArrayList<Prototype> protos) implements ProgramI{
         public <H, S> S accept(ProgramVisitor<H, S> v, H h) {
             return v.visitProgram(this, h);
         }
@@ -23,6 +23,15 @@ public class Program{
             return this.accept(llvmVisitor,new SymTable());
         }
     }
+    
+    //Prototype
+    public static record PrototypeImp(Type type, String nom, ArrayList<String> s) implements Prototype{
+        @Override
+        public <H, S> S accept(PrototypeVisitor<H, S> v, H h) {
+            return v.visitPrototype(this,h);
+        }
+
+    }
 
     //Fonction
     public static record FunctionImp(Type type, String nom, Instruction instruction)implements Function {
diff --git a/tests/aLaMain.vsl b/tests/aLaMain.vsl
index 6921373..446f575 100644
--- a/tests/aLaMain.vsl
+++ b/tests/aLaMain.vsl
@@ -1,3 +1,4 @@
+PROTO INT add(x,y)
 FUNC INT main() {
     INT a,b,c
     b:=3