diff --git a/datatype.go b/datatype.go
new file mode 100644
index 0000000..bd53649
--- /dev/null
+++ b/datatype.go
@@ -0,0 +1,23 @@
+package envconf
+type DataType int
+const (
+    TypeNone DataType = iota
+    TypeInt DataType = iota
+    TypeDuration DataType = iota
+    TypeString DataType = iota
+    TypeBool DataType = iota
+)
+
+func (dtype DataType) String()(string) {
+    types := make(map[DataType]string)
+    types[TypeNone] = "none"
+    types[TypeInt] = "int"
+    types[TypeDuration] = "duration"
+    types[TypeString] = "string"
+    types[TypeBool] = "bool"
+    str, ok := types[dtype]
+    if ok {
+        return str
+    }
+    return "invalid"
+}
diff --git a/main.go b/main.go
index f27b2c8..710ad8f 100644
--- a/main.go
+++ b/main.go
@@ -2,36 +2,35 @@ package envconf
 
 import ("strings"
         "unicode"
+        "strconv"
+        "time"
+        "errors"
+        "fmt"
         "os")
 
-type DataType int
-
-const (
-    TypeNone DataType = iota
-    TypeUnset DataType = iota
-    TypeInt DataType = iota
-    TypeDuration DataType = iota
-    TypeString DataType = iota
-)
-
 type cEntry struct {
     value string
+    parsed cValue
     dtype DataType
+    unset bool
+    empty bool
+}
+
+type cValue struct {
+    intval int64
+    durval time.Duration
+    strval string
+    err error
 }
 
 type Config struct {
+    parsed bool
     env map[string]cEntry
 }
 
-func getFirstRune(str string)(rune) {
-    for _,v := range str {
-        return v
-    }
-    return rune(0)
-}
-
 func NewConfig()(*Config) {
     config := new(Config)
+    config.parsed = false
     config.env = make(map[string]cEntry)
     for _,v := range os.Environ() {
         splitted := strings.SplitN(v, "=", 2)
@@ -41,6 +40,8 @@ func NewConfig()(*Config) {
                 var entry cEntry
                 entry.value = splitted[1]
                 entry.dtype = TypeNone
+                entry.unset = false
+                entry.empty = false
                 config.env[key] = entry
             }
         }
@@ -54,7 +55,64 @@ func (c *Config) Define(key string, dtype DataType) {
         entry.dtype = dtype
     } else {
         var entry cEntry
-        entry.dtype = TypeUnset
+        entry.dtype = dtype
+        entry.unset = true
+        entry.empty = true
         c.env[key] = entry
     }
 }
+
+func (c *Config) DefineDefault(key string, val string, dtype DataType) {
+    entry, ok := c.env[key]
+    if ok {
+        if entry.unset {
+            entry.empty = false
+            entry.value = val
+            entry.dtype = dtype
+        }
+    } else {
+        var entry cEntry
+        entry.dtype = dtype
+        entry.unset = true
+        entry.empty = false
+        c.env[key] = entry
+    }
+}
+
+func (c *Config) Parse() {
+    parsers := make(map[DataType](func(string)(cValue)))
+    parsers[TypeInt] = parseInt
+    parsers[TypeDuration] = parseDuration
+
+    for k,v := range c.env {
+        parser, ok := parsers[v.dtype]
+        if ok {
+            if v.empty {
+                if v.unset {
+                    v.parsed.err = errors.New(fmt.Sprintf("Environment variable %s not found. It should have been of type %s", k, v.dtype))
+                }
+            } else {
+                v.parsed = parser(v.value)
+            }
+        }
+    }
+}
+
+func parseInt(str string)(ret cValue) {
+    ret.intval, ret.err = strconv.ParseInt(str, 10, 64)
+    return
+}
+
+func parseDuration(str string)(ret cValue) {
+    ret.durval, ret.err = time.ParseDuration(str)
+    return
+}
+
+func getFirstRune(str string)(rune) {
+    for _,v := range str {
+        return v
+    }
+    return rune(0)
+}
+
+