Fun fact. The COM file size was limited to 64K. The program size was not. Most COM memory models set CS=DS=SS=ES. However, the Zortech C compiler, would have CS set differently.

CS pointed to the start of the code segment, DS to the start of the data segment. As long as the code segment plus the initialized data of the data segment was less than 64K, you could have a considerably larger runtime footprint (up to 128K) and still be a COM file with all near pointers.