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برمجة النظم

رابعة حاسب محاضرة (١٠)

دكتور/ أحمد الحربي

Specification of Data Structures

Figure 5.16 depicts the interplay between the two passes of a loader

in a direct-linking loading scheme.

The next step in our design procedure is to identify the data bases

required by each pass of the loader.

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Diagram describes the two passes of direct-linking loader scheme.

Format of Data Bases

` The third step in our design procedure is to specify the format

and content of each of the data bases. The major data bases are

depicted in the next figure (5.17).

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Object Deck:

The object deck has been discussed several times, depict in

detail and deck format that is used by various IBM 370 or 360

direct-linking loaders.

.المعلومات ول يتم توضيح الشكل التي تحفظ بهمن خالل ھذه الجدا

Global External Symbol Table:

المعرفة بـ external symbolsويستخدم ھذا الجدول لحفظ كل

A Segment Definition (SD) or Local Definition (LD) entry on an

External Symbol Dictionary (ESD) card.

:5.18ل لھذا الكرت تكون كما يلي بالشكل والتفاصي

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TXT card

:5.19والتفاصيل لھذا الكرت تكون كما يلي بالشكل

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RLD Card

:5.20والتفاصيل لھذا الكرت تكون كما يلي بالشكل

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END Card

:5.21والتفاصيل لھذا الكرت تكون كما يلي بالشكل

GEST Card

.Global External Symbolsھو عبارة عن جدول تحفظ به

Assigned core address 4-bytes

External Symbol 8-bytes

104

124

134

168

184

PG1bbbbb

PG1ENT1b

PG1ENT2b

PG2bbbbb

PG2ENT1b

Notation: This sample GEST content is based upon the example in Figure 5.12 and 5.15

0

20

30

0

16

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Figure 5.22 Global External Symbol Table (GEST) format

Local External Symbol Array

In pass 2 of the loader the GEST and ESD information for each

individual object deck is merged to produce the local external symbol

array that directly relates ID number and value. Figure 5.23 depicts the

format of the Local External Symbol Array (LESA).

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