diff --git a/du3/program.c b/du3/program.c
index f4994b2..e0006b3 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -2,6 +2,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <ctype.h>
+#include <string.h>
 
 #define SIZE 128
 
@@ -10,21 +11,21 @@
 int IsArithCorrect(float num1, float num2, char* op, float result)
 {
 
-    switch (op)
+    switch (*op)
     {
-        case '-'
+        case '-':
         if ((num1-num2) == result) { return 1;}
         break;
 
-        case '+'
+        case '+':
         if ((num1-num2) == result) { return 1;}
         break;
 
-        case '*'
+        case '*':
         if ((num1*num2) == result) { return 1;}
         break;
 
-        case '/'
+        case '/':
         if (num2 == 0) { return -1;}
         if ((num1-num2) == result) { return 1;}
         break;
@@ -60,11 +61,11 @@ int main()
 
             for (int i = 0; i != '\0'; i++)
             {
-                if (isdigit(i) != 0) 
+                if (isdigit(strBuffer[i]) != 0) 
                 {
                     //skontroluj, ze ci char po nom je tiez cislo, AK NIE, povazuj buduce cisla v riadku ako ine cislo 
                     // a inkrementuj kontrolnu citaciu premenu
-                    if (isdigit(i+1) == 0) 
+                    if (isdigit(strBuffer[i+1]) == 0) 
                     {
                         writeIntoArrayNum += 1;
                     }
@@ -86,7 +87,7 @@ int main()
                     continue;
                 }
 
-                if (ispunct() != 0)
+                if (ispunct(strBuffer[i]) != 0)
                 {
                     //ak je to nejaky printable symbol ('*/-,:./), skontroluj ci to nie je artimeticke znamienko alebo desatinna bodka,
                     //AK NIE, povazuj za riadok neplatny...
@@ -121,7 +122,7 @@ int main()
                     continue;
                 }
 
-                if (isalpha(i) != 0)
+                if (isalpha(strBuffer[i]) != 0)
                 {
                     isLineInvalid = true;
                     break;