File content as of revision 0:97a47026da17:

// Simple substring demo using only the default MBED library
// Theo@Ekelmans.com (NL)

#include "mbed.h"

Serial usbUART ( USBTX, USBRX );

void substring(char *s,char *d,int pos,int len) {
//usage: substring(Source,Destination,pos,len);

    char *t;

    s=s+(pos-1);
    t=s+len;
    while (s!=t) {
        *d=*s;
        s++;
        d++;
    }
    *d='\0';
}


int main() {
    usbUART.baud(115200);
    usbUART.printf("%c", 12);

    char Source[50]="working with strings is fun 0123456789 9876543210";
    char Destination[50];
    int pos,len;

    usbUART.printf("----------------------------------------------------------\r\n");
    usbUART.printf("                 substring demo                           \r\n");
    usbUART.printf("----------------------------------------------------------\r\n");
    usbUART.printf("source: %s\r\n", Source);
    usbUART.printf("----------------------------------------------------------\r\n");
    printf("input the start position, tap enter, input length, tap enter ");
    scanf("%d%d",&pos,&len);
    printf("\n\n");

    substring(Source,Destination,pos,len);
    
    printf("s= %s\n\r", Source);
    printf("d= %s\n\r", Destination);

}