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Annotation of coherent/a/usr/man/ALL/address, revision 1.1.1.1

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                      3: address                     Definition                    address
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                      8: An address  is the location  where an item  of data is  stored in
                      9: memory.
                     10: 
                     11: On the  i8086, a physical address is a  20-bit number.  The i8086
                     12: builds an  address by left-shifting  a 16-bit segment  address by
                     13: four bits,  and then adding  it to a 16-bit  offset address.  The
                     14: segment  address points  to a  particular  chunk of  memory.  The
                     15: i8086 uses  four segment registers, each of  which governs a dif-
                     16: ferent portion of a program, as follows:
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                     18: 
                     19:              CS      Address of code segment
                     20:              DS      Address of data segment
                     21:              ES      Address of ``extra'' segment
                     22:              SS      Address of stack segment
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                     24: 
                     25: SMALL-model programs  use only  the offset address;  hence, their
                     26: pointers are  only 16  bits long,  equivalent to an  iinntt.  LARGE-
                     27: model programs use  both segment and offset addresses.  Their ad-
                     28: dresses  are 20  bits  long, which  must  be stored  in a  32-bit
                     29: pointer, equivalent to a lloonngg.  COHERENT currently supports SMALL
                     30: model.
                     31: 
                     32: On  the M68000,  an address  is simply a  24-bit integer  that is
                     33: stored as  a 32-bit integer.   The upper eight  bits are ignored;
                     34: this is  not true with the more  advanced microprocessors in this
                     35: family,  such as  the M68020.  The  M68000 uses  no segmentation;
                     36: memory is organized as a ``flat address space'', with no restric-
                     37: tions set on the size of code or data.
                     38: 
                     39: On machines  with memory-mapped I/O, such as  the 68000, some ad-
                     40: dresses  may be  used to control  or communicate  with peripheral
                     41: devices.
                     42: 
                     43: ***** Example *****
                     44: 
                     45: The following printes the address and contents of a given byte of
                     46: memory.
                     47: 
                     48: 
                     49: #include <stdio.h>
                     50: 
                     51: main()
                     52: {
                     53:         char byte = 'a';
                     54:         printf("Address == %x\tContents == \"%c\"\n",
                     55:                 &byte, byte);
                     56: }
                     57: 
                     58: 
                     59: ***** See Also *****
                     60: 
                     61: data formats, definitions, pointer
                     62: 
                     63: 
                     64: COHERENT Lexicon                                           Page 1
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                     68: 
                     69: address                     Definition                    address
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                     73: 
                     74: ***** Notes *****
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                     76: COHERENT is in i8086 SMALL model; thus, its addresses are 16 bits
                     77: long.
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                    130: COHERENT Lexicon                                           Page 2
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