Quick injection of data in C without 3rd party functions -

this code made. objective @ first make abcdef appear on screen least amount of code possible given abc 1 memory space , def memory space.

#include "stdio.h"  void catstring3(){     char space[10];     char toadd[5]={'d','e','f','\0'};     char *string=space;     char *addon=toadd;     *string++='a';     *string++='b';     *string++='c';     *string++='def' // how?     *string++='\0';     string=space;     printf("result: %s\n",string); }  void catstring(){     char space[10];     char toadd[5]={'d','e','f','\0'};     char *string=space;     char *addon=toadd;     *string++='a';     *string++='b';     *string++='c';     while (*addon!='\0'){     *string++=*addon++;     }     *string++='\0';     string=space;     printf("result: %s\n",string); }  void catstring2(){     char space[10];     char *string=space;     *string++='a';     *string++='b';     *string++='c';     *string++='d';     *string++='e';     *string++='f';     *string++='\0';     string=space;     printf("result: %s\n",string); }  int main(int argc,char* argv[]){     catstring();     catstring2();     catstring3();     return 0; } 

of functions, feel function catstring2 produce slowest results because i'm setting values of each string space , added 1 line of code (one line per character of string). catstring bit cleaner processing wise, still same. catstring3 not execute @ //how? line because in conventional c can't assign string variable expecting one-character value.

what want assign @ least 2 bytes of data string pointer @ least 2 bytes modified @ once in string without use of third party functions such strcpy , memcpy , strcat.

anyone know easiest way or stuck setting 1 character @ time?