Enumerate data structures used during 1-pass of assembler, Computer Engineering

Assignment Help:

Enumerate the data structures used during the first pass of the assembler. Indicate the fields of these data structures and their purpose/usage.

Three main data structures used throughout the first pass of the assembler are given below:

- LOCCTR i.e. Location counter

- OPTAB i.e. operation code table

- SYMTAB i.e. Symbol table

LOCCTR: It is Location Counter that maintains track machine addresses of symbolic tables.

  • Initialized with START.
  • Raised for all instructions
  • Pseudo Instructions are: BYTE, WORD, RESB and RESW.
  • Machine Instructions are: Fixed length (i.e. 3 bytes) for SIC, variable length for SIC/XE (looking up OPTAB).
  • Allocate the value (address) of LOCCTR to consequent symbol table.

OPTAB: In this operation table mnemonic operation code and have its machine language equivalent.

346_OPTAB.png

  OPTAB can be implemented by using hashing function for fast access.

  SYMTAB: in Symbol table symbolic label, operand and their consequent machine are keeps addresses.

656_SYMTAB.png

  • SYMTAB is dynamic, constructed throughout Pass 1:

                   a. For symbolic label, fill in address and symbol (as per to current LOCCTR).

                   b. For symbolic operand, fill into symbol and mark this as undefined. Address field will be challenged later.

  • SYMTAB can be implemented by using hashing function for fast access.

Related Discussions:- Enumerate data structures used during 1-pass of assembler

Add the equation by using 648 and 487 in bcd code, Add 648 and 487 in BCD c...

Add 648 and 487 in BCD code. Ans. In BCD Code, addition of 648 and 487: 6 4 8  =  0 1 1 0   0 1 0 0      1 0 0 0 4 8 7  =  0 1 0 0   1 0 0 0      0 1 1 1 ---------------------

Concept development of project, Concept Development Journal General In...

Concept Development Journal General Information: Once you have researched and gained some insight into the topic you must then begin developing your ideas and your conceptua

Define how ptrace is used by debuggers, State how Shared Memory is used for...

State how Shared Memory is used for inter process communication. Define how ptrace is used by debuggers.  What are modules? Explain how data mapping takes place among modules

Define process control block, Define Process Control Block (PCB). Pr...

Define Process Control Block (PCB). Process Control Block (PCB): Information related with each process is stored into Process control Block. a)      Process state b)

What is input - output instructions, Q. What is Input - Output Instructions...

Q. What is Input - Output Instructions? An I/O instruction is stored in memory of computer and is fetched as well as executed by processor producing an I/O-related command for

What is electronic cash, What is electronic cash? E-cash is cash which ...

What is electronic cash? E-cash is cash which is shown by two models. One is the on-line form of e-cash which permits for the completion of all types of internet transactions.

Interpreted language and a compiled language, Difference between an interpr...

Difference between an interpreted language and a compiled language? Ans) A compiled language is written and then run by a compiler which checks its syntax and compresses it int

Determine grade of service is given worse service or not, The larger the Gr...

The larger the Grade of Service, the worse is the service given, it is true or false. Ans: It is true that larger the Grade of Service, the worse service is provided.

Explain program interpretation process, Explain program interpretation pr...

Explain program interpretation process. In a program interpretation process , the interpreter reads the source program and stores this in its memory. This bridges an executi

Describe the difference between cache and virtual memory, Question 1: (...

Question 1: (a) What do you meant by an expert system? (b) Describe benefits of the EDI. (c) Describe what you understand by: (i) File Infectors (ii) Boot Sect

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd