Page 142 - DCAP507_SYSTEM_SOFTWARE

System Software

Notes {
fscanf(fp1, "%s%lx", input, &loc);
while((strcmp(input, "R")!=0))
{
strcpy(table[count].csect, "");
strcpy(table[count].sym_name, input);
table[count].add=loc+start;
table[count++].length=0;
fscanf(fp1, "%s%lx", input, &loc);
}
while(strcmp(input, "T")!=0)
fscanf(fp1, "%s", input);
}
if(strcmp(input, "T")==0)
while(strcmp(input, "E")!=0)
fscanf(fp1, "%s", input);
fscanf(fp1, "%s", input);
start=start+length;
}
for(i=0; i<count; i++)
fprintf(fp2, "%s\t%s\t%lx\t%d\n", table[i].csect, table[i].sym_name,
table[i].add, table[i].length);
printf("\nPass 1 of Direct Linking Loaded is completed");
getch();
}

Pass 2 – Load Text and Relocate/Link Address Constants

After all the segments have been allocate locations and the external symbols have been defined
by pass 1, it is possible to complete the loading by loading the text and changing (relocation or
linking) address constants. At the end of pass 2, the loader will transmit control to the loaded
program. The following simple rule is frequently used to find out where to begin execution:
1. If an address is stated on the END record, that address is used as the implementation start address.

2. Or else, execution will begin at the beginning of the first segment
At the starting of pass 2 the program load address is initialized as in pass 1, and the execution
start address

(EXADDR) is set to IPLA. The records are read one by one from the object file left by pass 1.
All of the five types of records is processed in a different way, as follows:

ESD Records

Each of the ESD record types is processed in a different way.

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