Address operator and pointers, Operating System

Assignment Help:

  We are use to using variables within C without thinking about where they are stored. Most variables are dynamic i.e. can change, therefore they are stored in Ram, unlike a program once developed is static i.e. doesn't change; this is often storage in EPROM or Rom. We can directly access the address where the variable is stored by means of the address operator '&' .This returns the address of the variable followed i.e.

printf("The address of var A is %lx and the contents of var A is %x",&a,a) 
 
This address is often fixed by the compiler and cannot be altered easily, very often we want initialize the address of a variable and vary it, C uses the concept of the pointer to handle this. A pointer is a variable which holds an address (This is in fact an address register on the 68Hc11 i.e. X, Y). We can explicitly load up the variable with any number (address which we like) and perform simple mathematical functions on it i.e. add, mul, sub etc. In order to declare the variable as a pointer we need to prefix it with a * in its declarations i.e.

      int *point;  
      char *point; 
      float *point;

The type of pointer  used describes the size of the data to be read  i.e. a char pointer reads 7 bits of data , unsigned char 8 bits i.e. (some programmers use sizeof function to get actual machine size).

    char * point  == 7 bits
     unsigned char * point  == 8 bits
     int * point  == 15 bits
     unsigned int  * point  == 16 bits
     float * point  == 31 bits
     unsigned float  * point  == 32 bits


Related Discussions:- Address operator and pointers

Monolithic, What is monolithic and its diagram

What is monolithic and its diagram

Difference between message passing and shared memory, Problem: a) To en...

Problem: a) To ensure proper operation, the operating system and all the other programs must be protected from any malfunctioning program. Describe a mechanism which is impleme

Explain two level directory, Two Level Directory This kind of structure...

Two Level Directory This kind of structure overcomes the problems of assigning unique names to the files. Thus there need not be any confusion among users. In this kind of s

What is belady anomaly, What is Belady's anomaly When plotting on a g...

What is Belady's anomaly When plotting on a graph the page faults versus the number of available frames. We notice that the number of faults for four frames is greater than th

Linear programming problem, A paper mill produces two grades of paper viz.,...

A paper mill produces two grades of paper viz., X and Y. Because of raw material restrictions, it cannot produce more than 400 tons of grade X paper and 300 ton

Developing code with threads, Developing Code with Threads Writing code...

Developing Code with Threads Writing code to support a thread-based implementation is very straightforward. Simple APIs are presented to the developer for each threads package.

Transfer time, A hard-disk drive reads “120 GB HDD 7200 rpm 3 GB/sec transf...

A hard-disk drive reads “120 GB HDD 7200 rpm 3 GB/sec transfer rate”. If the drive has a sector size of 512 bytes, what is the average rotational latency and transfer time to read

Explain kernel-level threads (klt), KERNEL-LEVEL THREADS (KLT) In this...

KERNEL-LEVEL THREADS (KLT) In this level every thread management is done by kernel .No thread library except an API system calls to the kernel thread facility exists. The kern

Which of the subsequent instructions should be privileged, Q. Which of the ...

Q. Which of the subsequent instructions should be privileged? a) Read the clock b) Clear memory c) Set value of timer d) Issue a trap instruction e) Turn off interr

What are two probable uses of these multiple modes, Q. Several CPUs provide...

Q. Several CPUs provide for more than two modes of operation. What are two probable uses of these multiple modes? Answer: Although most systems merely distinguish between use

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