diff --git a/Lab04/content/part1/analyse/main.go b/Lab04/content/part1/analyse/main.go
index 1152a17..e366ca0 100644
--- a/Lab04/content/part1/analyse/main.go
+++ b/Lab04/content/part1/analyse/main.go
@@ -1,14 +1,15 @@
 package main
 
 import (
+	"flag"
 	"fmt"
 	"github.com/dariubs/percent"
 	"gonum.org/v1/plot"
 	"gonum.org/v1/plot/plotter"
 	"gonum.org/v1/plot/plotutil"
 	"gonum.org/v1/plot/vg"
-	"io/ioutil"
 	"log"
+	"os"
 	"sort"
 	"strings"
 )
@@ -26,27 +27,39 @@ func (l letterList) Len() int {
 	return len(l)
 }
 
-func (l letterList) Less(i, j int) bool {
-	return l[i].frequency > l[j].frequency
+func (l letterList) Less(firstIndex, secondIndex int) bool {
+	return l[firstIndex].frequency > l[secondIndex].frequency
 }
 
-func (l letterList) Swap(i, j int) {
-	l[i], l[j] = l[j], l[i]
+func (l letterList) Swap(firstIndex, secondIndex int) {
+	l[firstIndex], l[secondIndex] = l[secondIndex], l[firstIndex]
 }
 
 const lettersInTheAlphabet = 'Z' - 'A' + 1
 
 var letters = make([]letter, lettersInTheAlphabet)
 
-func initLetterStruct() {
+func init() {
 	for i := 0; i < lettersInTheAlphabet; i++ {
 		letters[i].upperCase = string(rune('A' + i))
 		letters[i].lowerCase = string(rune('A' + i + 32))
 	}
 }
 
+func parseArguments() string {
+	var inputFile string
+	flag.StringVar(&inputFile, "f", "", "Specify file to analyse.")
+	flag.Parse()
+	if inputFile == "" {
+		log.Print("No flag provided\n\nHelp:\n")
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+	return inputFile
+}
+
 func readFile(relativePath string) string {
-	content, err := ioutil.ReadFile(relativePath)
+	content, err := os.ReadFile(relativePath)
 	if err != nil {
 		log.Fatalln(err)
 	}
@@ -100,15 +113,14 @@ func plotResult() {
 		xAxisNaming = append(xAxisNaming, letters[index].upperCase)
 	}
 	p.NominalX(xAxisNaming...)
-	if err := p.Save(25*vg.Centimeter, 15*vg.Centimeter, "barChart.png"); err != nil {
+	if err = p.Save(25*vg.Centimeter, 15*vg.Centimeter, "barChart.png"); err != nil {
 		log.Fatalln(err)
 	}
 }
 
 func main() {
-	initLetterStruct()
-	//totalCount := countLetters(readFile("plaintext.txt"))
-	totalCount := countLetters(readFile("../encrypt/output.txt"))
+	inputFile := parseArguments()
+	totalCount := countLetters(readFile(inputFile))
 	calculateFrequency(totalCount)
 	plotResult()
 	sort.Sort(letterList(letters))
diff --git a/Lab04/content/part1/encrypt/main.go b/Lab04/content/part1/encrypt/main.go
index 00b43ec..11e5683 100644
--- a/Lab04/content/part1/encrypt/main.go
+++ b/Lab04/content/part1/encrypt/main.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"flag"
-	"io/ioutil"
 	"log"
 	"os"
 	"regexp"
@@ -27,7 +26,7 @@ func parseArguments() (string, string) {
 }
 
 func readFile(relativePath string) string {
-	content, err := ioutil.ReadFile(relativePath)
+	content, err := os.ReadFile(relativePath)
 	if err != nil {
 		log.Fatalln(err)
 	}