diff --git a/Caesar Ciper.c b/Caesar Ciper.c
new file mode 100644
index 0000000..e9bfba6
--- /dev/null
+++ b/Caesar Ciper.c	
@@ -0,0 +1,73 @@
+#include<ctype.h>
+#include <stdlib.h>
+#include<stdio.h>
+#include<string.h>
+
+typedef char* string;
+
+//Declaration of Encryping and Number Checker Function
+string encryptCaesar(string plainText, int key);
+int isNumber(string s);
+
+int main(int argc, string argv[])
+{
+    //Check for Command Line Arguments
+    int key = 0;
+    if (argc == 2 && isNumber(argv[1]))
+    {
+        key = atoi(argv[1]);
+    }
+    else
+    {
+        printf("Usage: ./caesar key\n");
+        return 1;
+    }
+
+    //Getting Plain Text from User
+    string plainText; 
+    printf("plaintext: ");
+    gets(plainText);
+
+    //Getting Caesar Cipher by Calling method
+    string cipherText = encryptCaesar(plainText, key);
+    printf("ciphertext: %s\n", cipherText);
+    return 0;
+}
+
+//Definition of Caesar Ciper Function
+string encryptCaesar(string plainText, int key)
+{
+    string cipherText = malloc(sizeof(plainText));
+    for (int i = 0, n = strlen(plainText); i <= n; i++)
+    {
+        if (plainText[i] >= 97 && plainText[i] <= 122)
+        {
+            int a = ((int)plainText[i] - 97 + key) % 26;
+            cipherText[i] = (int)(97 + a);
+        }
+        else if (plainText[i] >= 65 && plainText[i] <= 90)
+        {
+            int a = ((int)plainText[i] - 65 + key) % 26;
+            cipherText[i] = (int)(65 + a);
+        }
+        else
+        {
+            cipherText[i] = plainText[i];
+        }
+    }
+    return cipherText;
+}
+
+//Function for Checking Number
+int isNumber(string s)
+{
+    for (int i = 0, n = strlen(s); i < n; i++)
+    {
+        if (!isdigit(s[i]))
+        {
+            return 0;
+        }
+    }
+    //checking for non negative keys
+    return atoi(s) > 0;
+}