diff --git a/app/data/file.txt b/app/data/file.txt
new file mode 100644
index 0000000..b45ef6f
--- /dev/null
+++ b/app/data/file.txt
@@ -0,0 +1 @@
+Hello, World!
\ No newline at end of file
diff --git a/app/data/zadanie01/sum.txt b/app/data/zadanie01/sum.txt
index e69de29..615088b 100644
--- a/app/data/zadanie01/sum.txt
+++ b/app/data/zadanie01/sum.txt
@@ -0,0 +1 @@
+108
\ No newline at end of file
diff --git a/app/data/zadanieDnia/test.txt b/app/data/zadanieDnia/test.txt
index 47c17e3..315424d 100644
--- a/app/data/zadanieDnia/test.txt
+++ b/app/data/zadanieDnia/test.txt
@@ -4,4 +4,4 @@ Foreword
 Kyle Simpson is a thorough pragmatist.
 
 I can't think of higher praise than this. To me, these are two of the most important qualities that a software developer must have. That's right: must, not should. Kyle's keen ability to tease apart layers of the JavaScript programming language and present them in understandable and meaningful portions is second to none.
-[https://github.com/getify/You-Dont-Know-JS/blob/master/es6%20%26%20beyond/foreword.md]
\ No newline at end of file
+[https://github.com/getify/You-Dont-Know-JS/blob/master/es6%20%26%20beyond/foreword.md]
diff --git a/app/data/zadanieDnia/test2.txt b/app/data/zadanieDnia/test2.txt
new file mode 100644
index 0000000..f7a3d88
--- /dev/null
+++ b/app/data/zadanieDnia/test2.txt
@@ -0,0 +1,7 @@
+YoU DoN'T KnOw jS: eS6 & bEyOnD
+FoReWoRd
+
+KyLe sImPsOn iS A ThOrOuGh pRaGmAtIsT.
+
+I CaN'T ThInK Of hIgHeR PrAiSe tHaN ThIs. To mE, tHeSe aRe tWo oF ThE MoSt iMpOrTaNt qUaLiTiEs tHaT A SoFtWaRe dEvElOpEr mUsT HaVe. ThAt's rIgHt: MuSt, NoT ShOuLd. KyLe's kEeN AbIlItY To tEaSe aPaRt lAyErS Of tHe jAvAsCrIpT PrOgRaMmInG LaNgUaGe aNd pReSeNt tHeM In uNdErStAnDaBlE AnD MeAnInGfUl pOrTiOnS Is sEcOnD To nOnE.
+[HtTpS://GiThUb.cOm/gEtIfY/YoU-DoNt-kNoW-Js/bLoB/MaStEr/eS6%20%26%20bEyOnD/FoReWoRd.mD]
diff --git a/app/zadanie01.js b/app/zadanie01.js
index 8c20173..8c84e1e 100644
--- a/app/zadanie01.js
+++ b/app/zadanie01.js
@@ -1 +1,18 @@
-//Twój kod
\ No newline at end of file
+const fs = require('fs');
+const path = './data/zadanie01';
+fs.readFile(`${path}/input.json`, 'utf8', (error, data) => {
+    if (error) {
+        console.error('Błąd podczas odczytu pliku!', error);
+    } else {
+        const arrayOfNumbers = JSON.parse(data);
+        let arraySum = 0;
+        arrayOfNumbers.forEach((value) => arraySum += value);
+        fs.writeFile(`${path}/sum.txt`, arraySum, err => {
+            if (err === null){
+                console.info('Zapisano poprawnie!');
+            } else {
+                console.error('Błąd podczas zapisu pliku!', err);
+            }
+        });
+    }
+});
diff --git a/app/zadanie02.js b/app/zadanie02.js
index 8c20173..45dafbd 100644
--- a/app/zadanie02.js
+++ b/app/zadanie02.js
@@ -1 +1,12 @@
-//Twój kod
\ No newline at end of file
+const fs = require('fs');
+
+fs.readdir('./data/zadanie02', (err, files) => {
+    if (err === null){
+        console.log('Lista plików:');
+        files.forEach(file => {
+            console.log(file);
+        });
+    } else {
+        console.log('Błąd podczas listowania katalogu!', err);
+    }
+});
diff --git a/app/zadanieDnia.js b/app/zadanieDnia.js
index 8c20173..92666ce 100644
--- a/app/zadanieDnia.js
+++ b/app/zadanieDnia.js
@@ -1 +1,23 @@
-//Twój kod
\ No newline at end of file
+//Twój kod
+const fs = require('fs');
+const fileName = process.argv[2];
+const path = `./data/zadanieDnia/${fileName}`;
+
+fs.readFile(path, 'utf8', (error_read, data) => {
+    if (error_read === null){
+        let content = '';
+        for (let i = 0; i < data.length; i += 1){
+            console.log('znak data[i] =', data[i]);
+            content += (i % 2 === 0) ? data[i].toUpperCase() : data[i].toLowerCase();
+        }
+        fs.writeFile(`./data/zadanieDnia/test2.txt`, content, error_write => {
+            if (error_write === null){
+                console.log('zapisno plik.');
+            } else {
+                console.log('blad zapisu:', error_write);
+            }
+        });
+    } else {
+        console.log('nie udalo sie odczytac pliku =', error_read);
+    }
+});