HP 3000 Manuals HP 3000 Manuals
Packed Arrays
Table 5-3 shows how the HP Pascal packing algorithm allocates and
aligns the elements of a packed array. The element types are in
alphabetical order.
Table 5-3. Allocation and Alignment of Packed Array Elements
(HP Pascal Packing Algorithm)
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| | | |
| Element Type | Allocation | Alignment |
| | | |
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| | | |
| Anyptr | 8 bytes | 4-bytes |
| | | |
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| | | |
| Array, crunched | Same as crunched array that is not part of an array | Byte |
| | or record (see Table 5-9 ); then padded to the | |
| | nearest byte. | |
| | | |
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| | | |
| Array, packed | Same as packed array that is not part of an array | Same as element, |
| | or record (find element type in this table and use | or byte, |
| | formula in section "Arrays" ); then padded to | whichever is |
| | alignment boundary. | larger. |
| | | |
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| | | |
| Array, unpacked | Same as unpacked array that is not part of an array | Same as element. |
| | or record (find element type in this table and use | |
| | formula in section "Arrays" ). | |
| | | |
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| | | |
| Bit16 | 2 bytes | 2-byte |
| | | |
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| | | |
| Bit32 | 4 bytes | 4-byte |
| | | |
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| | | |
| Bit52 | 8 bytes | 4-byte |
| | | |
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| | | |
| Boolean | 1 bit | 1 bit |
| | | |
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| | | |
| Char | 1 byte | 1-byte |
| | | |
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| | | |
| Enumeration | See "Enumerations and Subranges" . | |
| | | |
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| | | |
| File | See "Files". | 8-byte |
| | | |
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| | | |
| Function | 8 bytes | 4-byte |
| | | |
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| | | |
| Integer | 4 bytes | 4-byte |
| | | |
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| | | |
| Globalanyptr | 8 bytes | 4-byte |
| | | |
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| | | |
| Localanyptr | 4 bytes | 4-byte |
| | | |
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| | | |
| Longint | 8 bytes | 4-byte |
| | | |
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| | | |
| Longreal | 8 bytes | 8-byte |
| | | |
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| | | |
| Pointer | 4 bytes | 4-byte |
| | | |
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| | | |
| Procedure | 8 bytes | 4-byte |
| | | |
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| | | |
| Real | 4 bytes | 4-byte |
| | | |
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| | | |
| Record, crunched | Fields are allocated by type, and record is padded | Byte |
| | to byte boundary. | |
| | | |
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Table 5-3. Allocation and Alignment of Packed Array Elements
(HP Pascal Packing Algorithm) (cont.)
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| | | |
| Element Type | Allocation | Alignment |
| | | |
-----------------------------------------------------------------------------------------------
| | | |
| Record, packed | Fields are allocated by type, and record is padded | Largest alignment |
| | to the alignment boundary. | boundary of any |
| | | field, or byte, |
| | | whichever is |
| | | larger. |
| | | |
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| | | |
| Record, unpacked | Fields are allocated by type, and record is padded | Largest alignment |
| | to the alignment boundary. | boundary of any |
| | | field. |
| | | |
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| | |
| Set | See "Sets" . |
| | |
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| | | |
| Shortint | 2 bytes | 2-byte |
| | | |
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| | | |
| Strings | See "Strings" . | 4-byte |
| | | |
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| | |
| Subrange | See "Enumerations and Subranges" . |
| | |
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Example
VAR
uba : ARRAY [1..3] OF Boolean;
pba : PACKED ARRAY [1..3] OF Boolean;
The array uba takes three bytes:
![[]](../../pic3k/M010194/FFN283c50.gif)
The array pba takes three bits:
![[]](../../pic3k/M010194/FFN293c50.gif)
If an array is not within a crunched structure, the compiler aligns the
entire array on the same boundary as its first element, or on a byte
boundary.
Declaring an array PACKED has no effect on its elements if the elements
are unpacked structures.