What is the purpose of these two lines : ? word(p):=sizeof(mytype);
In real mode TP it sets the offset of the segment:offset pair to 1.
Probably it originally was meant as a simple inc(p);
The problem it expects that the offset part of a newly allocated block is always zero, which is afaik not true. (real mode TP allocates per half segment).
p:=pchar(p)+2;
inc(p,2); or p:=@p[2];
The overall effect therefore is inc(p,3); or p:=pchar(p)[3];