pleae explain why i m not able to compare

Question

i tried to compare str[i]=='i' so that i can find it is a vowel or not but it is not comparing it.my problem is to compare a string character and change them to their next alphabet (like a to b) and if they are vowel i have to change them to uppercase...now help me...
here is my code...
int size=strlen(str);
for(int i=0;i<size;i++)
{
int flag=0;
if(str[i]=='a'||str[i]=='e'||str[i]=='i'||str[i]=='o'||str[i]=='u')flag=1;
char str[i]++;

if(flag==1)str[i]=toupper(str[i]);

}
all requied hearder files are added now help mee pls

Answer 1

there is no flag = 1; in your code

Answer 2

oh..my mistake...now it ia ok