Describe program control instructions, Computer Engineering

Assignment Help:

Q. Describe Program Control Instructions?

These instructions specify conditions for altering the sequence of program execution or we can say in other words that the content of PC (program counter) register.  PC points to memory location which holds the subsequent instruction to be executed. The alteration in value of PC as a result of execution of control instruction such as BRANCH or JUMP causes a break in sequential execution of instructions. The most common control instructions are as following:

JUMP and BRANCH may be unconditional or conditional. JUMP is an unconditional branch used to implement simple loops. JNE jump not equal is conditional branch instruction. The conditional branch instructions like BRP X and BRN X causes a branch to memory location X if the result of most recent operation is positive or negative correspondingly. If the condition is true PC is loaded with branch address X and next instruction is taken from X otherwise PC is not changed and the subsequent instruction is taken from location pointed by PC. Figure below displays an unconditional branch instruction and a conditional branch instruction if content of AC is zero.

MBR←0; Assign 0 to MBR register

X←2001; Assume X to be an address location 2001

READ X; Read a value from memory location 2001 into AC

BRZ 1007; Branch to location 1007 if AC is zero (Conditional branch on zero)

ADD MBR; add the content of MBR to AC and store result to AC

TRAS MBR; Transfer the contents of AC to MBR 

INC X; Increment X to point to next location 

JUMP 1001;Loop back for further processing.


Related Discussions:- Describe program control instructions

Explain about the e-commerce over extranets, Explain about the e-commerce o...

Explain about the e-commerce over extranets. Extranets are regarding “joining up” the supply chain-suppliers, distributors, resellers and customers are enabling business-to bus

Estimate the natural frequency and damping factor, On the Moodle site just ...

On the Moodle site just below the assignment you will find data from a slow sine sweep test conducted on a car on a "four-post" road simulator for the frequency range 0 to 20 Hz in

What are the event key words in interactive reporting, What are the event k...

What are the event key words in interactive reporting? Event Keyword                                                 Event AT LINE-SELECTION         Moment at which the u

What is functional modelling, What is  Functional Modelling  We know ...

What is  Functional Modelling  We know that Data flow modelling is an ordinary technique used for analysis of a problem in software engineering. It is very useful for analyzi

What is a zombie, What is a zombie? When a program forks and the child ...

What is a zombie? When a program forks and the child finishes before the parent, the kernel still keeps some of its information about the child in case the parent might require

How can you show only selected records with a form, How can you show only s...

How can you show only selected records with a form? There are dissimilar ways in which you can limit the records that you will see with a form, you can: Open a form and app

When can a user program execution be interrupted, When can a user program e...

When can a user program execution be interrupted? It won't be desirable to interrupt a program when an instruction is being executed and is in a state such as instruction decod

Write a subroutine in c which toggles the cursor, Q . Write a subroutine in...

Q . Write a subroutine in C which toggles the cursor? Write a subroutine in C which toggles the cursor. It takes one argument which toggles the value between on (1) and off (0)

Explain token ring, Explain Token Ring. Token Ring: A token ring is ...

Explain Token Ring. Token Ring: A token ring is a collection of single point -to-point links, which arise from a circle. In a token ring a special bi t pattern, termed as th

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