strings and pointer

[shinjianata]

I have been asked to make a program which can change lowercase letter to upper case without using any given functions from C libraries ( for example toupper from string.h ). It should work like this
Input string to capitalised: input
Enter line of txt : input is wrong
INPUT is wrong.
What I have done is above, do help please!!

#include <stdio.h>
#define maxlen 80
main ()
{
    char line1 [maxlen +1];
    char   string[80];
    char i,c;
    char *str;                    
    char *line=0;
    void readline (char *,int);
    void to_cap_str(char *, char *);
    printf ("Input String to Capitalise:");
    scanf ("%s",string);
    printf ("Enter a line of txt:\n");
    scanf ("%s",line1);
    str = string;
    line = line1;
    to_cap_str(line,str);
    readline (line, maxlen);       
}
void readline (char *line,int length)
{
    int i=0,c;
    while (i++ <length &&(c = getchar ()) != '\n' && c != EOF)
    *line++ = c;
    *line ='\0';
}
void to_cap_str(char *line, char *str)
{
    int i=-1,c=0;
    *str++ = c;
    for (c=0; c<i; c++)
    {
    if (c==i)
    {
        i=i-32;
        i++;
    }
 
    else break;
    }    
    *line++ = i;
}
 

[shinjianata]

I for got to mention that program will not terminated until CTRL+D is issued

[AdrianH]

I for got to mention that program will not terminated until CTRL+D is issued

Well you have done a good job of it so far. Your readline() is a bit convoluted but it should work (personally I'd have built my format string and used scanf(), but to each their own, yours might be faster, though faster doesn't usually mean much in user input unless you are writing a game).

Your main problem appears to be in to_cap_str(). I'm not sure what you are trying to attempt, but the loop will never execute as c<i is always false (c=0, i=-1).

What you should try is to make a to_cap_str() that capitalises the first n chars in a c-string, and make a find_str() funciton to find the beginning of a string that you want to captilise. Then loop over the string with these functions.

In this way you have broken down the problem into more manageable parts, with each being far more attainable and testable.

NOTE: A C-String is interesting as you can pass a sub string from anywhere in it to the terminating null by passing the address of an indexed element. I.e.

char str[]="Hello there.";
char * substr = &str[6];
printf("%s", substr);  // output "there."
 

Hope this helps.


Adrian