diff --git a/src/main/antlr4/de/hsrm/compiler/Klang/Klang.g4 b/src/main/antlr4/de/hsrm/compiler/Klang/Klang.g4
index 9d76fbe..d895218 100644
--- a/src/main/antlr4/de/hsrm/compiler/Klang/Klang.g4
+++ b/src/main/antlr4/de/hsrm/compiler/Klang/Klang.g4
@@ -52,6 +52,7 @@ arguments
 
 atom
   : INTEGER_LITERAL #intAtom
+  | IDENT # variable
   ;
 
 PRINT: 'print';
diff --git a/src/main/java/de/hsrm/compiler/Klang/ContextAnalysis.java b/src/main/java/de/hsrm/compiler/Klang/ContextAnalysis.java
index 7efd07f..f2a62d2 100644
--- a/src/main/java/de/hsrm/compiler/Klang/ContextAnalysis.java
+++ b/src/main/java/de/hsrm/compiler/Klang/ContextAnalysis.java
@@ -87,6 +87,11 @@ public class ContextAnalysis extends KlangBaseVisitor<Node> {
     return result;
   }
 
+  @Override
+  public Node visitVariable(KlangParser.VariableContext ctx) {
+    return new Variable(ctx.IDENT().getText());
+  }
+
   @Override
   public Node visitAtomExpression(KlangParser.AtomExpressionContext ctx) {
     return this.visit(ctx.atom());
diff --git a/src/main/java/de/hsrm/compiler/Klang/nodes/expressions/Variable.java b/src/main/java/de/hsrm/compiler/Klang/nodes/expressions/Variable.java
new file mode 100644
index 0000000..fd99e82
--- /dev/null
+++ b/src/main/java/de/hsrm/compiler/Klang/nodes/expressions/Variable.java
@@ -0,0 +1,18 @@
+package de.hsrm.compiler.Klang.nodes.expressions;
+
+import de.hsrm.compiler.Klang.visitors.Visitor;
+
+public class Variable extends Expression {
+
+    public String name;
+
+    public Variable(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public <R> R welcome(Visitor<R> v) {
+        return v.visit(this);
+    }
+
+}
\ No newline at end of file
diff --git a/src/main/java/de/hsrm/compiler/Klang/visitors/EvalVisitor.java b/src/main/java/de/hsrm/compiler/Klang/visitors/EvalVisitor.java
index fedb689..cd639a2 100644
--- a/src/main/java/de/hsrm/compiler/Klang/visitors/EvalVisitor.java
+++ b/src/main/java/de/hsrm/compiler/Klang/visitors/EvalVisitor.java
@@ -1,13 +1,20 @@
 package de.hsrm.compiler.Klang.visitors;
 
+import java.util.HashMap;
+import java.util.Map;
+
 import de.hsrm.compiler.Klang.Value;
 import de.hsrm.compiler.Klang.nodes.Block;
 import de.hsrm.compiler.Klang.nodes.FunctionDefinition;
+import de.hsrm.compiler.Klang.nodes.Program;
 import de.hsrm.compiler.Klang.nodes.expressions.*;
 import de.hsrm.compiler.Klang.nodes.statements.*;
 
 public class EvalVisitor implements Visitor<Value> {
 
+  Map<String, FunctionDefinition> funcs = new HashMap<>();
+  Map<String, Value> env = new HashMap<>();
+
   @Override
   public Value visit(IntegerExpression e) {
     return new Value(e.value);
@@ -40,6 +47,17 @@ public class EvalVisitor implements Visitor<Value> {
     return new Value(-a.asInteger());
   }
 
+  @Override
+  public Value visit(Variable e) {
+    Value result = this.env.get(e.name);
+
+    if (result == null) {
+      throw new RuntimeException("Variable with name " +e.name + " not found.");
+    }
+
+    return result;
+  }
+
   @Override
   public Value visit(IfStatement e) {
     // In the future we have to make sure that the
@@ -69,22 +87,55 @@ public class EvalVisitor implements Visitor<Value> {
 
   @Override
   public Value visit(Block e) {
+    Value result = null;
     for (var stmt : e.statements) {
-      stmt.welcome(this);
+      result = stmt.welcome(this);
     }
-    return null;
+    return result;
   }
 
   @Override
   public Value visit(FunctionDefinition e) {
-    // TODO Auto-generated method stub
-    return null;
+    // Ein Eval über eine FunDef macht keinen Sinn
+    throw new RuntimeException("Wir sind im Eval und visiten eine Funktionsdefinition.. WUT?!");
   }
 
   @Override
   public Value visit(FunctionCall e) {
-    // TODO Auto-generated method stub
-    return null;
+    // Die funktionsdefinition speichern
+    FunctionDefinition func = this.funcs.get(e.name);
+
+    // Stelle sicher, dass die Länge der argumente und parameter übereinstimmen
+    if (e.arguments.length != func.parameters.length) {
+      throw new RuntimeException("Error with function call " +e.name + ": Number of parameters wrong");
+    }
+
+    // Baue ein neues environment
+    Map<String, Value> newEnv = new HashMap<>();
+    for (int i = 0; i < func.parameters.length; i++) {
+      newEnv.put(func.parameters[i], e.arguments[i].welcome(this));
+    }
+    var oldEnv = this.env;
+    this.env = newEnv;
+
+    // Execute
+    Value result = func.block.welcome(this);
+
+    // Das alte env wiederherstellen
+    this.env = oldEnv;
+
+    return result;
+  }
+
+  @Override
+  public Value visit(Program e) {
+    // Funktionsdefinitionen für die Auswertung
+    // von Funktionsaufrufen speichern
+    for (var funcDef: e.funcs) {
+      this.funcs.put(funcDef.name, funcDef);
+    }
+
+    return e.expression.welcome(this);
   }
 
 }
\ No newline at end of file
diff --git a/src/main/java/de/hsrm/compiler/Klang/visitors/PrettyPrintVisitor.java b/src/main/java/de/hsrm/compiler/Klang/visitors/PrettyPrintVisitor.java
index 8fd2849..5f655d4 100644
--- a/src/main/java/de/hsrm/compiler/Klang/visitors/PrettyPrintVisitor.java
+++ b/src/main/java/de/hsrm/compiler/Klang/visitors/PrettyPrintVisitor.java
@@ -55,13 +55,13 @@ public class PrettyPrintVisitor implements Visitor<Void> {
 
     @Override
     public Void visit(Program e) {
-      for (var funcDef : e.funcs) {
-        funcDef.welcome(this);
-        ex.nl();
-        ex.nl();
-      }
-      e.expression.welcome(this);
-      return null;
+        for (var funcDef : e.funcs) {
+            funcDef.welcome(this);
+            ex.nl();
+            ex.nl();
+        }
+        e.expression.welcome(this);
+        return null;
     }
 
     @Override
@@ -139,40 +139,46 @@ public class PrettyPrintVisitor implements Visitor<Void> {
         return null;
     }
 
-  @Override
-  public Void visit(FunctionDefinition e) {
-    ex.write("function ");
-    ex.write(e.name);
-    ex.write(" (");
-    boolean first = true;
-    for (String param : e.parameters) {
-      if (!first) {
-        ex.write(", ");
-      } else {
-        first = false;
-      }
-      ex.write(param);
+    @Override
+    public Void visit(FunctionDefinition e) {
+        ex.write("function ");
+        ex.write(e.name);
+        ex.write(" (");
+        boolean first = true;
+        for (String param : e.parameters) {
+            if (!first) {
+                ex.write(", ");
+            } else {
+                first = false;
+            }
+            ex.write(param);
+        }
+        ex.write(") ");
+        e.block.welcome(this);
+        return null;
     }
-    ex.write(") ");
-    e.block.welcome(this);
-    return null;
-  }
 
-  @Override
-  public Void visit(FunctionCall e) {
-    ex.write(e.name);
-    ex.write("(");
-    boolean first = true;
-    for (Expression arg : e.arguments) {
-      if (!first) {
-        ex.write(", ");
-      } else {
-        first = false;
-      }
-      arg.welcome(this);
+    @Override
+    public Void visit(FunctionCall e) {
+        ex.write(e.name);
+        ex.write("(");
+        boolean first = true;
+        for (Expression arg : e.arguments) {
+            if (!first) {
+                ex.write(", ");
+            } else {
+                first = false;
+            }
+            arg.welcome(this);
+        }
+        ex.write(");");
+        return null;
+    }
+
+    @Override
+    public Void visit(Variable e) {
+        ex.write(e.name);
+        return null;
     }
-    ex.write(");");
-    return null;
-  }
 
 }
\ No newline at end of file
diff --git a/src/main/java/de/hsrm/compiler/Klang/visitors/Visitor.java b/src/main/java/de/hsrm/compiler/Klang/visitors/Visitor.java
index 29017d2..7c2efd8 100644
--- a/src/main/java/de/hsrm/compiler/Klang/visitors/Visitor.java
+++ b/src/main/java/de/hsrm/compiler/Klang/visitors/Visitor.java
@@ -8,6 +8,7 @@ import de.hsrm.compiler.Klang.nodes.statements.*;
 
 public interface Visitor<R> {
     R visit(IntegerExpression e);
+    R visit(Variable e);
     R visit(MultiplicativeExpression e);
     R visit(AdditiveExpression e);
     R visit(NegateExpression e);