Answer Posted / antonio leite

extern states that a variable is referenced in a module but
is declared in another module. This makes the linker not
generate an error/warning when the extern variable is
referenced but wait till the declaration is stated in a
module.
volatile states that the value of a variable can be changed
anywhere in the code. This is used by the optimizer to know
that a piece of code must not be optimized when a volatile
variable is found. For example, when a variable is changed
by a interrupt timer it must be declared volatile. The code
seems to be always true because Timer_xpto seems to be
always > 0. If the code is optimized, the if would simply
disapper from the code, but this is not what the programmer
wants, so declare
extern volatile unsigned long Timer_xpto;
so that the compiler will never optimize the code below.

Timer_xpto = 100;
do something
if (Timer_xpto > 0 )
{
do any other thing
}

Here extern is stating that the variable is declared in
other module and volatile that the code where the
Timer_xpto appears must not be optimized.
See http://www.eetimes.com/discussion/programming-
pointers/4025609/Place-volatile-accurately

Do you know pointer in c?

1104

---

What is the use of a static variable in c?

1105

---

Differentiate between calloc and malloc.

1317

---

what is the role you expect in software industry?

2197

---

Explain c preprocessor?

1155

---

main() { struct s1 { char *str; struct s1 *ptr; }; static struct s1 arr[] = { {"Hyderabad",arr+1}, {"Bangalore",arr+2}, {"Delhi",arr} }; struct s1 *p[3]; int i; < BR> for(i=0;i<=2;i++) p[i] = arr[i].ptr; printf("%s ",(*p)->str); printf("%s ",(++*p)->str); printf("%s ",((*p)++)->str); }

1506

---

What is %d used for?

1087

---

can anyone please tell about the nested interrupts?

2182

---

Write a program to print “hello world” without using semicolon?

1179

---

Write a C/C++ program that connects to a MySQL server and checks if the InnoDB plug-in is installed on it. If so, your program should print the maximum number of concurrent threads that the InnoDB plug-in can create.

1993

---

You are to write your own versions of strcpy() and strlen (). Call them mystrcpy() and mystrlen(). Write them first as code within main(), not as functions, then, convert them to functions. You will pass two arrays to the function in the case of mystrcpy(), the source and target array.

2402

---

What does. int *x[](); means ?

1132

---

What is time complexity c?

1040

---

How can I read data from data files with particular formats?

1091

---

What is oops c?

1337

---