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return 0 vs return 1


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nismo

Mon Aug 11 2008, 08:49AM

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Does anyone knows what does return 1 does?

shyam

Mon Aug 11 2008, 12:03PM

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Joined: Mon Aug 06 2007, 11:33AM

Posts: 725
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suppose u have a fun say add

you can use return as follows..

CODE:

int add(void);

main()

{

printf("sum of 2 and 3 is %d ",add());

}

int add(void)

{

return 5;

}

thus we can say return 1 returns a 1

[ Edited Wed Aug 13 2008, 03:31AM ]

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Ajay

Tue Aug 12 2008, 04:31AM

Rickey's World Admin

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In programming language, return 0 and return 1 are used to return the status of function.

return 0 <- return false
return 1 <- return true

ex.

CODE:

int greater (int a, int b){

   if(a>b)

      return 1;

   return 0;

}

void main(){

    if(greater(3,2)){

         printf("its greater");

     } else

         printf("its smaller");

}

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nismo

say2paul

Tue Aug 12 2008, 04:54AM

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Joined: Tue Jun 17 2008, 10:56AM

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The return statement

A return statement ends the processing of the current function and returns control to the caller of the function.

CODE:

>>-return--+--------------------------+--;---------------------><

           '-+---+--expression--+---+-'

             '-(-'              '-)-'

A value-returning function should include a return statement, containing an expression. C only If an expression is not given on a return statement in a function declared with a non-void return type, the compiler issues a warning message. C++ If an expression is not given on a return statement in a function declared with a non-void return type, the compiler issues an error message.

If the data type of the expression is different from the function return type, conversion of the return value takes place as if the value of the expression were assigned to an object with the same function return type.

For a function of return type void, a return statement is not strictly necessary. If the end of such a function is reached without encountering a return statement, control is passed to the caller as if a return statement without an expression were encountered. In other words, an implicit return takes place upon completion of the final statement, and control automatically returns to the calling function. C++ If a return statement is used, it must not contain an expression.
Examples of return statements

The following are examples of return statements:

CODE:

return;            /* Returns no value            */

return result;     /* Returns the value of result */

return 1;          /* Returns the value 1         */

return (x * x);    /* Returns the value of x * x  */

The following function searches through an array of integers to determine if a match exists for the variable number. If a match exists, the function match returns the value of i. If a match does not exist, the function match returns the value -1 (negative one).

CODE:

int match(int number, int array[ ], int n)

{

   int i;

   for (i = 0; i < n; i++)

      if (number == array[i])

         return (i);

   return(-1);

}

A function can contain multiple return statements. For example:

CODE:

void copy( int *a, int *b, int c)

{

   /* Copy array a into b, assuming both arrays are the same size */

   if (!a || !b)       /* if either pointer is 0, return */

      return;

   if (a == b)         /* if both parameters refer */

      return;          /*    to same array, return */

   if (c == 0)         /* nothing to copy */

      return;

   for (int i = 0; i < c; ++i;) /* do the copying */

      b[i] = a[1];

                       /* implicit return */

}

In this example, the return statement is used to cause a premature termination of the function, similar to a break statement.

An expression appearing in a return statement is converted to the return type of the function in which the statement appears. If no implicit conversion is possible, the return statement is invalid.

Source: XL C/C++ V8.0 IBM

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nismo

pdi33

Tue Aug 12 2008, 06:42AM

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Joined: Mon Jun 04 2007, 09:28AM

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Another interesting application of the return function is when it is used in the main() function. Here the return (value) returns the value to the operating system which is used by the operating system for its own use (especially when unix operating system is used.)
but this feature is not applicable in our real time embedded system where the control never reaches the return statement.

* inspired to develop,developing to inspire *

nismo

Tue Aug 12 2008, 09:17AM

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Joined: Thu Jul 31 2008, 09:03AM

Posts: 77
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very clear

no wonder my lecturer told me India has a lot of good programmers.. Thanks

[ Edited Tue Aug 12 2008, 09:19AM ]

nismo

Tue Aug 12 2008, 09:27AM

Registered Member #9479

Joined: Thu Jul 31 2008, 09:03AM

Posts: 77
Thanked 1 time in 1 posts

void copy( int *a, int *b, int c)
{
/* Copy array a into b, assuming both arrays are the same size */

if (!a || !b) /* if either pointer is 0, return */
return;

if (a == b) /* if both parameters refer */
return; /* to same array, return */

if (c == 0) /* nothing to copy */
return;

for (int i = 0; i < c; ++i;) /* do the copying */
b[i] = a[1];
/* implicit return */
}

Yoyo, Mr say2paul... what does the return does in this routine? Does it mean return to the main function?

pdi33

Tue Aug 12 2008, 12:01PM

Registered Member #1329

Joined: Mon Jun 04 2007, 09:28AM

Posts: 770
Thanked 185 times in 180 posts

hi nismo,
well, if u have called the function copy ( ) from the main function, then it will return back to the main function. but if the function was called by another function say abc() then the control will return to that function.

case1: calling from main function

main()
{
.
copy (....);
. <------- control will return here
.
}

case2: calling from another function

main()
{
.
.
abc(...);
.
.
}

abc()
{
.
.
copy();
. <------ control will return here
.
}

* inspired to develop,developing to inspire *