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

What are the advantages of linked allocation, What are the advantages of Li...

What are the advantages of Linked allocation? The benefits are a. No external fragmentation b. Size of the file does not require to be declared

What is the translation look aside buffer (tlb), Translation Look aside Buf...

Translation Look aside Buffer In a cached system, the base addresses of the last few indexed pages is maintained in registers named the TLB that adds in faster lookup. TLB has

Explain single level directory structure, Single level directory: This ...

Single level directory: This is the easiest directory structure. All the files are controlled in the same directory, which is simple to support and understand. Few of the li

What is the purpose of system calls, What is the purpose of system calls? ...

What is the purpose of system calls? System calls permit user-level processes to request services of the operating system.

Operating system, The term Operating System (OS) is often misused. It is co...

The term Operating System (OS) is often misused. It is common, for example, for people to speak of an OS when they are in fact referring to an OS and to a set of additional applica

What is a path name, What is a path name? A pathname is the path from t...

What is a path name? A pathname is the path from the root by all subdirectories to a specified file. In a two-level directory structure a user name and a file name explain a pa

Difference among pre-emptive and non pre-emptive scheduling, Q. Define the ...

Q. Define the difference among pre-emptive and non pre-emptive scheduling. Answer: Pre-emptive scheduling permits a process to be interrupted in the midst of its execution ta

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