Word Processor

I am trying to create a program that a common error that users often make is that they forget the caps locks on an print text like this: "tHIS IS A SAMPLE of an error", this usually happens at the beginning of a new sentence. Write a program to detect this error and fix it. The input will be a long string on keyboard. Basically I am trying to change: "tHIS IS A SAMPLE of an error" to "This is a simple of an error." The only error I got is "isalpha"

#include <stdio.h>

#include <string.h>



main()

{

char sent [30];

int length=0, i=0, capCount=0, endLoop=0;

printf ("Enter sentence up to 30 characters:\n" );

gets (sent);

length=strlen(sent);

for (i=0; i<length; i=i+1)

{

if (sent[i]>65 && sent [i]<91)

{

capCount= capCount+1;

sent[i]=sent[i]+32;

}

}

for(i = 0; i < length && endLoop == 0; i++)

{

if(isalpha(sent[i]))

{

sent[i] -= 32;

endLoop = 1;

}

}

printf("--------------------------------------\n" );

printf("There was(were) %d capitalized letters.\n" , capCount);

printf("The sentence after ridding the caps is as follows:\n" );

printf(" %s\n", sent);

getchar();

getchar();

return 0;

}