C Making the First Letter Uppercase

Question

I wanted to write a code which makes a uppercase of first letter of string 1 and 3 and printing those.

1. I tried the code below this but compiler gives İNVALİD CONVERSİON OF CHAR TO İNT

2. What is wrong with this code should i try with strlen and for loop? This is code;

   int main()
   { 
     char str1[] = "elektrik";
     char str2[] = "ve";
     char str3[] = "elektronik";
   
     str1 = toupper(str1);
     str3 = toupper(str3);
     printf("%s %s %s",str1,str2,str3);
     getch();
   
     return 0;
   
   }
   

Answer 1

You need

*str1 = toupper(*str1);

...

Asssuming that str1 is a pointer to char (and include the appropriate header files)