Page 77 - DCAP507_SYSTEM_SOFTWARE

Unit 4: Design of Assembler

 After all the symbols have been depicted by pass 1, it is probable to terminate the assembly Notes
by processing each record and determining values for its operation code and its operand
field.
 Instead of observing the assembler as a single program (of 1,000 to 10,000 source statements),
we examine it as a coordinated collection of routines each of relatively minor size and
complexity.

4.3 Keywords

Absolute Addresses: These are the address fields that will not require to be customized by the
loader.
Assembler: 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.
Pass 1: Pass 1 requires only name, format, and length.

Pass 2: Pass 2 needs a Machine Operation Table containing name, length, binary code, and
format.
Relocatable Addresses: These 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.

4.4 Review Questions

1. What is an assembler? Discuss the function of assembler.

2. Illustrate various Addressing Options used in designing assembler.
3. Enlighten the steps on assembling a program with example.
4. How can we group tasks into two passes? Illustrate the purpose of pass 1 and pass 2.

5. Make distinction between pass 1 database and pass 2 databases.
6. Draw the Structure Flowchart for assembler pass 1 and assembler pass 2.
7. Explain the process of identifying the format and content of each of the databases.
8. How do you define symbols in pass 1? Write an algorithm to explain.
9. Explain the process of generating code with the help of an algorithm.

10. Illustrate the concept of modularity in designing assembler.

Answers: Self Assessment

1. Assembler 2. Absolute addresses
3. Relocatable addresses 4. Indirect
5. DATA 6. input

7. machine operation 8. Pass 1
9. simplifying 10. format
11. assembly 12. length

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