diff --git a/cmd/iffmaster/main.go b/cmd/iffmaster/main.go
index d77032c..5778b1b 100644
--- a/cmd/iffmaster/main.go
+++ b/cmd/iffmaster/main.go
@@ -1,6 +1,15 @@
 // Copyright (c) 2025 Matthias Rustler
 // Licensed under the MIT License - see LICENSE for details
 
+/*
+Iffmaster is a tool to inspect IFF files as defined under EA-85.
+
+Usage:
+
+	iffmaster
+
+There aren't any command line options yet.
+*/
 package main
 
 import "github.com/mattrust/iffmaster/internal/gui"
diff --git a/internal/chunks/chunk.go b/internal/chunks/chunk.go
index 4db230c..f2b55c3 100644
--- a/internal/chunks/chunk.go
+++ b/internal/chunks/chunk.go
@@ -1,6 +1,7 @@
 // Copyright (c) 2025 Matthias Rustler
 // Licensed under the MIT License - see LICENSE for details
 
+// Package chunks provides functions to read IFF files.
 package chunks
 
 import (
@@ -13,6 +14,7 @@ import (
 	"fyne.io/fyne/v2"
 )
 
+// IFFChunk represents a chunk in an IFF file.
 type IFFChunk struct {
 	// the chunk data from the file
 	ID    string
@@ -31,7 +33,10 @@ type IFFChunk struct {
 	ChType string
 }
 
+// ReadIFFFile reads an IFF file and returns the root chunk.
+// In case of an error, the function returns nil and the error.
 func ReadIFFFile(reader fyne.URIReadCloser) (*IFFChunk, error) {
+	// TODO: get rid of fyne.URIReadCloser
 	var chunk *IFFChunk
 
 	file, err := os.Open(reader.URI().Path())
@@ -51,7 +56,10 @@ func ReadIFFFile(reader fyne.URIReadCloser) (*IFFChunk, error) {
 	return chunk, err
 }
 
+// readChunkID reads the ID of a chunk from the reader.
+// In case of an error, the function returns an empty string and the error.
 func readChunkID(reader io.Reader) (string, error) {
+	//TODO: check for valid characters
 	var id [4]byte
 	_, err := reader.Read(id[:])
 	if err != nil {
@@ -61,6 +69,8 @@ func readChunkID(reader io.Reader) (string, error) {
 	return string(id[:]), nil
 }
 
+// readChunkSize reads the size of a chunk from the reader.
+// In case of an error, the function returns 0 and the error.
 func readChunkSize(reader io.Reader) (uint32, error) {
 	var size uint32
 	err := binary.Read(reader, binary.BigEndian, &size)
@@ -71,6 +81,8 @@ func readChunkSize(reader io.Reader) (uint32, error) {
 	return size, nil
 }
 
+// readChunk recursively reads the chunks from the reader.
+// In case of an error, the function returns nil and the error.
 func readChunk(reader io.Reader, parentChunk *IFFChunk, maxSize int64, level int) (*IFFChunk, error) {
 	var chunk IFFChunk
 	var err error
@@ -159,6 +171,8 @@ func readChunk(reader io.Reader, parentChunk *IFFChunk, maxSize int64, level int
 	return &chunk, nil
 }
 
+// PrintIffChunk prints the chunk and its children to stdout.
+// The level parameter must be set to 0.
 func PrintIffChunk(chunk *IFFChunk, level int) {
 	for i := 0; i < level; i++ {
 		fmt.Print("  ")
@@ -169,6 +183,7 @@ func PrintIffChunk(chunk *IFFChunk, level int) {
 	}
 }
 
+// isGeneric returns true if the chunk ID is generic.
 func isGeneric(id string) bool {
 
 	return slices.Contains([]string{"ANNO", "AUTH", "CHRS",
diff --git a/internal/chunks/database.go b/internal/chunks/database.go
index 075bcf2..0712862 100644
--- a/internal/chunks/database.go
+++ b/internal/chunks/database.go
@@ -7,13 +7,19 @@ import (
 	"fmt"
 )
 
+// StructResult is a list of key-value pairs.
 type StructResult [][2]string
+
+// ChunkHandler is a function that processes a chunk and returns the structured data.
 type ChunkHandler func(data []byte) (StructResult, error)
+
+// ChunkData contains the handler and the description for each chunk type.
 type ChunkData struct {
 	Handler     ChunkHandler
 	Description string
 }
 
+// structData contains the handler and the description for each chunk type.
 var structData = map[string]ChunkData{
 	// generic chunks
 	"(any).ANNO": {handleAnyIso8859, "Annotation"},
@@ -137,6 +143,11 @@ var structData = map[string]ChunkData{
 	"YUVN": {nil, "YUV Image Data"},
 }
 
+// GetStructData returns the description and the structured data of a chunk.
+// - chType is the chunk type, e.g. "ILBM", "ILBM.BMHD"
+// - data is the chunk data
+// It returns the description and the structured data as a list of key-value pairs.
+// In case of an error the incomplete result is returned.
 func GetStructData(chType string, data []byte) (string, StructResult, error) {
 	var result StructResult
 	var description string
@@ -161,6 +172,9 @@ func GetStructData(chType string, data []byte) (string, StructResult, error) {
 	return description, result, err
 }
 
+// getBeUword reads a big-endian unsigned WORD from the data at the given offset.
+// The offset is incremented by 2.
+// In case of an error, it returns 0 and the error. The offset is unchanged.
 func getBeUword(data []byte, offset *uint32) (uint16, error) {
 	var result uint16
 
@@ -172,6 +186,9 @@ func getBeUword(data []byte, offset *uint32) (uint16, error) {
 	return result, nil
 }
 
+// getBeWord reads a big-endian signed WORD from the data at the given offset.
+// The offset is incremented by 2.
+// In case of an error, it returns 0 and the error. The offset is unchanged.
 func getBeWord(data []byte, offset *uint32) (int16, error) {
 	var result int16
 
@@ -183,6 +200,9 @@ func getBeWord(data []byte, offset *uint32) (int16, error) {
 	return result, nil
 }
 
+// getBeUlong reads a big-endian unsigned LONG from the data at the given offset.
+// The offset is incremented by 4.
+// In case of an error, it returns 0 and the error. The offset is unchanged.
 func getBeUlong(data []byte, offset *uint32) (uint32, error) {
 	var result uint32
 
@@ -195,6 +215,9 @@ func getBeUlong(data []byte, offset *uint32) (uint32, error) {
 	return result, nil
 }
 
+// getBeLong reads a big-endian signed LONG from the data at the given offset.
+// The offset is incremented by 4.
+// In case of an error, it returns 0 and the error. The offset is unchanged.
 func getBeLong(data []byte, offset *uint32) (int32, error) {
 	var result int32
 
@@ -207,6 +230,9 @@ func getBeLong(data []byte, offset *uint32) (int32, error) {
 	return result, nil
 }
 
+// getUbyte reads an unsigned BYTE from the data at the given offset.
+// The offset is incremented by 1.
+// In case of an error, it returns 0 and the error. The offset is unchanged.
 func getUbyte(data []byte, offset *uint32) (uint8, error) {
 	var result uint8
 
@@ -218,6 +244,9 @@ func getUbyte(data []byte, offset *uint32) (uint8, error) {
 	return result, nil
 }
 
+// getByte reads a signed BYTE from the data at the given offset.
+// The offset is incremented by 1.
+// In case of an error, it returns 0 and the error. The offset is unchanged.
 func getByte(data []byte, offset *uint32) (int8, error) {
 	var result int8
 
diff --git a/internal/chunks/handle_8svx.go b/internal/chunks/handle_8svx.go
index 97a0aa9..3671fc0 100644
--- a/internal/chunks/handle_8svx.go
+++ b/internal/chunks/handle_8svx.go
@@ -8,6 +8,7 @@ import (
 	"log"
 )
 
+// handle8svxVhdr processes the 8SVX.VHDR chunk.
 func handle8svxVhdr(data []byte) (StructResult, error) {
 	log.Println("Handling 8SVX.VHDR chunk")
 
@@ -74,6 +75,7 @@ func handle8svxVhdr(data []byte) (StructResult, error) {
 	return result, nil
 }
 
+// handle8svxAtakRlse processes the 8SVX.ATAK or 8SVX.RLSE chunk.
 func handle8svxAtakRlse(data []byte) (StructResult, error) {
 	log.Println("Handling 8SVX.ATAK or 8SVX.RLSE chunk")
 
diff --git a/internal/chunks/handle_anim.go b/internal/chunks/handle_anim.go
index 66c2c60..f8c6097 100644
--- a/internal/chunks/handle_anim.go
+++ b/internal/chunks/handle_anim.go
@@ -8,6 +8,7 @@ import (
 	"log"
 )
 
+// handleAnimAnhd processes the ANIM.ANHD chunk.
 func handleAnimAnhd(data []byte) (StructResult, error) {
 	log.Println("Handling ANIM.ANHD chunk")
 
@@ -151,6 +152,7 @@ func handleAnimAnhd(data []byte) (StructResult, error) {
 	return result, nil
 }
 
+// handleAnimDpan processes the ANIM.DPAN chunk.
 func handleAnimDpan(data []byte) (StructResult, error) {
 	log.Println("Handling ANIM.DPAN chunk")
 
diff --git a/internal/chunks/handle_any.go b/internal/chunks/handle_any.go
index 795765d..d603d9d 100644
--- a/internal/chunks/handle_any.go
+++ b/internal/chunks/handle_any.go
@@ -7,6 +7,7 @@ import (
 	"golang.org/x/text/encoding/charmap"
 )
 
+// handleAnyIso8859 processes any chunk with ISO-8859-1 encoding.
 func handleAnyIso8859(data []byte) (StructResult, error) {
 	var result StructResult
 
@@ -19,6 +20,7 @@ func handleAnyIso8859(data []byte) (StructResult, error) {
 	return result, nil
 }
 
+// handleAnyUtf8 processes any chunk with UTF-8 encoding.
 func handleAnyUtf8(data []byte) (StructResult, error) {
 	var result StructResult
 
diff --git a/internal/chunks/handle_ilbm.go b/internal/chunks/handle_ilbm.go
index c99fd29..94f17e1 100644
--- a/internal/chunks/handle_ilbm.go
+++ b/internal/chunks/handle_ilbm.go
@@ -8,6 +8,7 @@ import (
 	"log"
 )
 
+// handleIlbmBmhd processes the ILBM.BMHD chunk.
 func handleIlbmBmhd(data []byte) (StructResult, error) {
 	log.Println("Handling ILBM.BMHD chunk")
 
@@ -109,6 +110,7 @@ func handleIlbmBmhd(data []byte) (StructResult, error) {
 	return result, nil
 }
 
+// handleIlbmCmap processes the ILBM.CMAP chunk.
 func handleIlbmCmap(data []byte) (StructResult, error) {
 	log.Println("Handling ILBM.CMAP chunk")
 
@@ -133,6 +135,7 @@ func handleIlbmCmap(data []byte) (StructResult, error) {
 	return result, nil
 }
 
+// handleIlbmGrab processes the ILBM.GRAB chunk.
 func handleIlbmGrab(data []byte) (StructResult, error) {
 	log.Println("Handling ILBM.GRAB chunk")
 
@@ -156,6 +159,7 @@ func handleIlbmGrab(data []byte) (StructResult, error) {
 	return result, nil
 }
 
+// handleIlbmCamg processes the ILBM.CAMG chunk.
 func handleIlbmCamg(data []byte) (StructResult, error) {
 	log.Println("Handling ILBM.CAMG chunk")
 
@@ -173,6 +177,7 @@ func handleIlbmCamg(data []byte) (StructResult, error) {
 	return result, nil
 }
 
+// handleIlbmDpi processes the ILBM.DPI chunk.
 func handleIlbmDpi(data []byte) (StructResult, error) {
 	log.Println("Handling ILBM.DPI chunk")
 
@@ -199,6 +204,7 @@ func handleIlbmDpi(data []byte) (StructResult, error) {
 	return result, err
 }
 
+// handleIlbmDest processes the ILBM.DEST chunk.
 func handleIlbmDest(data []byte) (StructResult, error) {
 	log.Println("Handling ILBM.DEST chunk")
 
@@ -242,6 +248,7 @@ func handleIlbmDest(data []byte) (StructResult, error) {
 	return result, nil
 }
 
+// handleIlbmSplt processes the ILBM.SPLT chunk.
 func handleIlbmSprt(data []byte) (StructResult, error) {
 	log.Println("Handling ILBM.SPRT chunk")
 
@@ -259,6 +266,7 @@ func handleIlbmSprt(data []byte) (StructResult, error) {
 	return result, nil
 }
 
+// handleIlbmCrng processes the ILBM.CRNG chunk.
 func handleIlbmCrng(data []byte) (StructResult, error) {
 	log.Println("Handling ILBM.CRNG chunk")
 
diff --git a/internal/chunks/handle_pefs.go b/internal/chunks/handle_pefs.go
index 5a9b3d2..58cfdda 100644
--- a/internal/chunks/handle_pefs.go
+++ b/internal/chunks/handle_pefs.go
@@ -8,6 +8,7 @@ import (
 	"log"
 )
 
+// handlePrefPrhd processes the PREF.PRHD chunk.
 func handlePrefPrhd(data []byte) (StructResult, error) {
 	log.Println("Handling PREF.PRHD chunk")
 
diff --git a/internal/gui/chunkview.go b/internal/gui/chunkview.go
index 1591dea..98ba3d8 100644
--- a/internal/gui/chunkview.go
+++ b/internal/gui/chunkview.go
@@ -11,6 +11,7 @@ import (
 	"golang.org/x/text/encoding/charmap"
 )
 
+// NewHexTableView creates a new fyne table for the hexadecimal view.
 func NewHexTableView(appData *AppData) *widget.Table {
 	table := widget.NewTable(
 		// Provide the size of the table
@@ -46,6 +47,7 @@ func NewHexTableView(appData *AppData) *widget.Table {
 	return table
 }
 
+// NewIsoTableView creates a new fyne table for the ISO-8859-1 view.
 func NewIsoTableView(appData *AppData) *widget.Table {
 	table := widget.NewTable(
 		// Provide the size of the table
@@ -82,6 +84,7 @@ func NewIsoTableView(appData *AppData) *widget.Table {
 	return table
 }
 
+// NewStructTableView creates a new fyne table for the structure view.
 func NewStructTableView(appData *AppData) *widget.Table {
 	table := widget.NewTable(
 		// Provide the size of the table
@@ -113,6 +116,8 @@ func NewStructTableView(appData *AppData) *widget.Table {
 	return table
 }
 
+// iso8859ToUtf8Char converts an ISO-8859-1 character to a UTF-8 string.
+// Some special characters are converted to escape sequences.
 func iso8859ToUtf8Char(isoChar byte) string {
 	// handle special characters
 	if isoChar == 0 {
diff --git a/internal/gui/gui.go b/internal/gui/gui.go
index cf37a3b..706e731 100644
--- a/internal/gui/gui.go
+++ b/internal/gui/gui.go
@@ -1,6 +1,7 @@
 // Copyright (c) 2025 Matthias Rustler
 // Licensed under the MIT License - see LICENSE for details
 
+// Package gui provides the GUI for the IFF Master application
 package gui
 
 import (
@@ -32,6 +33,7 @@ type AppData struct {
 	structTableView *widget.Table
 }
 
+// OpenGUI layouts the main window and opens it
 func OpenGUI() {
 	var appData AppData
 	var fileDlg *dialog.FileDialog
diff --git a/internal/gui/nodelistview.go b/internal/gui/nodelistview.go
index 90181e4..3de61e0 100644
--- a/internal/gui/nodelistview.go
+++ b/internal/gui/nodelistview.go
@@ -12,6 +12,8 @@ import (
 	"github.com/mattrust/iffmaster/internal/chunks"
 )
 
+// ListEntry is a struct to hold the data for the list view.
+// It embeds the IFFChunk struct to hold the chunk data.
 type ListEntry struct {
 	label            string
 	description      string
@@ -19,6 +21,8 @@ type ListEntry struct {
 	*chunks.IFFChunk // Embedding the IFFChunk struct
 }
 
+// NewListView creates a new fyne list view.
+// It creates a list widget with the chunk ID.
 func NewListView(appData *AppData) *widget.List {
 	list := widget.NewList(
 
@@ -48,6 +52,8 @@ func NewListView(appData *AppData) *widget.List {
 	return list
 }
 
+// ConvertIFFChunkToListNode traverses to a IFF chunk nodes and appends
+// data which is neede for ghe GUI.
 func ConvertIFFChunkToListNode(chunk *chunks.IFFChunk) []ListEntry {
 	var nodeList []ListEntry