Page 76 - DCAP507_SYSTEM_SOFTWARE

System Software

Notes 2. ........................... are the address fields that will not require to be customized by the loader.
3. ........................... are the addresses that will require to be accustomed if and only if the
loader choose to position this program at a dissimilar memory location than the assembler
allocated.
4. ........................... Addresses refers to a location in memory that comprises the target address.
5. The ........................... instruction is a directive asking the assembler to describe some data.

6. Since symbols can emerge before they are defined, it is suitable to make two passes over
the ............................
7. Pass 2 needs a ........................... Table containing name, length, binary code, and format.

8. ........................... requires only name, format, and length.
9. By ........................... the table formats, we could merge the tables into one table.
10. Once we decide what information fist in each database, it is essential to identify the
........................... of each entry.
11. The contents of fixed tables are not filled in or tainted during the ........................... process.
12. The ........................... field signifies the length (in bytes) of the instruction or data to which
the symbol is connected.
13. For every instruction in ..........................., we generate the equivalent machine language
instruction.

14. The reason of the ........................... pass is to allocate a location to every instruction and data
defining pseudo-instruction, and thus to define addresses/values for symbols occurring
in the label fields of the source program.
15. When the ........................... pseudo-op is encountered, pass 1 is finished.

4.2 Summary

 An assembler is a program that receives as input an assembly language program and
generates its machine language correspondent along with information for the linker/
loader and report for the consumer.

 Absolute addresses are the address fields that will not require to be customized by the
loader.
 Relocatable addresses are the addresses that will require to be accustomed if and only if
the loader choose to position this program at a dissimilar memory location than the
assembler allocated.

 Since symbols can emerge before they are defined, it is suitable to make two passes over
the input (as this example displays).
 Once we decide what information fist in each database, it is essential to identify the format
of each entry.
 The Symbol Table and Literal Table comprise for each entry the name and assembly-time
address/value fields but also a length field, usage field, and a relative position indicator.

 The reason of the first pass is to allocate a location to every instruction and data defining
pseudo-instruction, and thus to define addresses/values for symbols occurring in the
label fields of the source program.

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