Please help me.

Program has the following definition:

char string[] = "1234";

How do I make a program which converts numbers given in a string to integer without using the "atoi" -function?

My greatest problem is how to compare a single character in a string.
For example

if (string[0]=="1") // this naturally is wrong

Thanks in advance.

Mikko, Finland

Maybe this (rather nice looking) site will help. I've not touched C so this site will be more help than me :P

Eddie's Basic Guide To C Programming

In particular:
C - atoi, itoa, sprintf and sscanf
C - Copying Strings: strcpy, strncpy and strcmp - Using strcpy to Copy Strings, Using strncpy to Copy Strings, Using strcmp to Compare Strings

hi mikko,

In C we can't compare two strings using relational operators.But using strcmp() we can compare two strings. Instead of using if (string[0]=="1") you just use if(string[0]='1') to compate two chracters.you can convert a character in to number by subtracting character 'zero' or integer 48.




for(I=0;string[i]!='\0';i++)
{
int j=string[i]-'0';

num=num*10+j;

}

hi mikko,

In C we can't compare two strings using relational operators.But using strcmp() we can compare two strings. Instead of using if (string[0]=="1") you just use if(string[0]='1') to compate two chracters.you can convert a character in to number by subtracting character 'zero' or integer 48.




for(I=0;string[i]!='\0';i++)
{
int j=string[i]-'0';

num=num*10+j;

}

Hhhhhhhhhhhhhh