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

User threads control dispatching, Consider a particular system that does no...

Consider a particular system that does not have an interrupting clock.  The only way a thread can lose the processor is to voluntarily surrender it.  Additionally, the operating sy

Explain the demand paging system, Question : (a) In the demand paging ...

Question : (a) In the demand paging system, when a process tries to access a page that was not brought into memory, a page fault occurs that involves a series of actions. The

Allocation techniques, Since most of the programs require a lot of memory a...

Since most of the programs require a lot of memory allocation/deallocation, we expect the memory management to be fast, to have low fragmentation, make good use of locality, and be

How does windows xp execute transport protocols, Q. What kinds of networkin...

Q. What kinds of networking does Windows XP support? How does Windows XP execute transport protocols? Describe two networking protocols. Answer: Support is offer for bo

Operating system structure, Problem: (a) Modern operating systems are i...

Problem: (a) Modern operating systems are interrupt driven. If there are no processes to execute, no I/O devices to service, and no users to whom to respond, an operating syste

What are the common strategies to select a free hole, What are the common s...

What are the common strategies to select a free hole from a set of available holes? The most common methods are a. First fit b. Best fit c. Worst fit

Explain disadvantages of the two-level directory, How do we overcome the di...

How do we overcome the disadvantages of the two-level directory? Give links from one user directory to another, creating path names; system files become available by letting th

Process destruction, Most process abstractions support processes being dest...

Most process abstractions support processes being destroyed when the program terminates, or in response to a specific kill directive. There are two common implementations, one a "p

Research proposal, what topic i choose for os research proposal

what topic i choose for os research proposal

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