strings in C language

strings.c

#include <stdio.h>
unsigned scat(char *s, char *s2)
{
    int i,j;
    for(i=0;s[i]!=0; i++);
        s[i++]=32;
    for(j=0;s2[j]!=0;j++){
        s[i]=s2[j];
	i++;
    }
    s[i]=0;

}

unsigned slen (char *s)
{
    int i;
    for(i=0;s[i]!=0;i++);
    return i;
}

char* create(char *s,char *s2)
{

    static char s3[100];
    s3[0]=0;
    scat(s3,s);
    scat(s3,s2);
    printf(" ");
    return s3;
}

int main()
{

    char str1[50]="Alice";
    char str2[]="dog";
    char str3[]="Peter",str4[]="Cat";
    char *st1,*st2;
    st1=create(str1,str2);
    printf("st1=%s\nst1=%p\nst2=%s\nst2=%p\n\n",st1,st1,st2,st2);
    st2=create(str3,str4);
    printf("st2=%s\nst2=%p\nst1=%p\n\n",st2,st2,st1);

}