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main()
{
char *p1="Name";
char *p2;
p2=(char *)malloc(20);
while(*p2++=*p1++);
printf("%s\n",p2);
}
what is the output?
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Answer / sanath
ANS: NULL
It is a bit tricky question. If u observe carefully then we
are incrementing the pointers p1,p2. When it reached the end
of the string, *p2 points to NULL. We have lost the address
of the starting position.
| Is This Answer Correct ? | 40 Yes | 5 No |
Hi all,
#1 Mannucse's ans is wrong. cos as mentioned "Name" will
not be the output.
#2 Sanath's ans is wrong. Cos at the end of the while loop,
p2 will not point to NULL. It will point to the next byte
to the NULL termination ie., 6th byte.
#3 Shruti's ans is wrong. cos i think she got confused
between assignment(=) and comparisonal(==) operators. And
the statement given as "we cannot copy the value of p1 in
p2, the way its mentioned here" is absolutely wrong.
So,
Lets Analyse the program and how to get the required output.
hav a look on th program again.
main()
{
char *p1="Name";
char *p2;
p2=(char *)malloc(20);
while(*p2++ = *p1++)
{
printf("TEST \n");
}
printf("%s\n",p2);
getch();
}
Here, in every iteration of while loop, we are assigning
*p1 to *p2, and incrementing both pointers p1 and p2, After
completion(when *p1 value would be '\0')of the while loop,
first 5 bytes of p2 holds the
characters 'N','a','m','e' '\0'. At the end of while loop
p2 points to the 6th byte in the memory.
So, now printf("%s\n",p2); shall start print the values
from the 6th byte to 20th bytes of the memory which was
allocated dynamically.
----------------------------------
To get the desired output change the printf statement to
printf("%s\n",p2-5);
Now (p2-5) points to the starting address of p2 and will
print the values in the memory till it encounters '\0'
termination. ie., The output would be -> Name
| Is This Answer Correct ? | 9 Yes | 6 No |
In addtion to the answer #5.
printf("%s\n",p2); will print the values from 6th byte to
20th byte.
6th byte to 20th bytes of the memory will contain some
Garbage value. So the output will be a string of garbage
values.
For desired o/p see the ans #5
| Is This Answer Correct ? | 6 Yes | 3 No |
Answer / ali fakoor
A part of uninitialized (and/or unowned) memory after (and
including) the sixth byte of the malloc-ed memory will be
printed out until reaching a NULL character in the memory
somewhere!
| Is This Answer Correct ? | 6 Yes | 4 No |
int main()
{
char *p1="Name";
char *p2,*s1,*s2;;
p2=(char *)malloc(20);
s1 = p1;
s2 = p2;
while(*p2++ = *p1++);
printf("%s %s",s1,s2);
return 0;
}
Store the Start address of p1 and p2 before incrementing the pointer so that it could be later used to print the String.
| Is This Answer Correct ? | 1 Yes | 0 No |
-> while(*p2++ "=" *p1++)
the syntax of while is
while("condition");
in condition statement the assignment operator is used in a
wrong way..
when we are using loop it should be "=="..
we cannot copy the value of p1 in p2, the way its mentioned
here..
** It will either give an error or display some garbage
value in p2 , or no value..
depends on what p2 is initialised to implicitly..
| Is This Answer Correct ? | 1 Yes | 12 No |
What is the main difference between calloc () and malloc ()?
A variable that is defined in a specified portion of a program but can be used throughout the program a) global variable b) local variable c) character d) none
a parameter passed between a calling program and a called program a) variable b) constant c) argument d) all of the above
What are header files? What are their uses?
What's wrong with "char *p = malloc(10);" ?
what is a function prototype?
write aprogram for There is a mobile keypad with numbers 0-9 and alphabets on it. take input of 7 keys and then form a word from the alphabets present on those keys.
1 Answers iGate, Shashi, Source Bits, Subex,
consider the following structure: struct num nam{ int no; char name[25]; }; struct num nam n1[]={{12,"Fred"},{15,"Martin"},{8,"Peter"},{11,Nicholas"}}; ..... ..... printf("%d%d",n1[2],no,(*(n1 + 2),no) + 1); What does the above statement print? a.8,9 b.9,9 c.8,8 d.8,unpredictable value
Here is a neat trick for checking whether two strings are equal
Topics: Structures, Arrays, Searching and Sorting Assume there is a small mobile computer device including a hard disk and a slot for a memory card. The device shall be used to backup photos e.g. during holiday. Every time a memory card is connected all photos of the card are copied into a new folder automatically. And your task is to develop some basic controlling software to show, add, remove, search and sort the directories of photos. Step by Step Implementation 1.Define two symbolic constants, one to hold the total volume of the disk (e.g. VOLUME) and another one to hold the number of entries the files system of the device can handle (MAXFOLD). 2.Define a new structure data type named DATE to store a date consisting of year, month and day as unsigned values. 3.Define an other structure data type FOLDER to store the information of one folder of photos: ◦A title as character array of appropriate length ◦The location (event) the photos are taken as character array of appropriate length ◦The date of the day the photos are copied to the disk using the just defined data type DATE ◦The number of photos as natural number ◦And the size of the folder in MB as floating point value 4.Define the following global variables and initialise them: ◦disk as an array with MAXFOLD elements of data type FOLDER ◦folders as natural value to count the number of folders currently stored at the disk (valid elements in the array) TEST: Now you should be able to compile the code the first time without any warning or error. In the menu only "p" to print and "q" to quit will work!. 5.Now complete the functions given by their prototype: float freeSpace ();The function has to calculate the sum of the size component of all elements currently stored in the disk array. The function shall return the free space of the disk by the difference between the available total volume and the calculated sum. TEST: To test this function you only need to uncomment printing the "statusline" at the function actionmenu(). Compare the calculated value with a manual calculation of the example values given above. unsigned isBefore (DATE, DATE);The function checks if one date is before the other. There are 3 different possibilities which have to be handled. Imagine for example these 3 different combinations of values: ◦2010-01-01 : 2010-01-02 ◦2010-01-01 : 2010-02-01 ◦2010-01-01 : 2009-01-01 The function shall just return the result of the comparison. unsigned isEqual (DATE, DATE);The function checks if one date is equal to the other, all components have to be compared. The function shall just return the result of the comparison. int findByDate (DATE);As the array is should be kept in order (sorted by date) implement a binary search for a folder by its date here. You need only to adapt the binary search we used in the exercise. Use the 2 comparing functions above where appropriate. The function shall return the index of the element which was found or -1. TEST: Now you can try searching a folder by date via the "s" in the menu. Activate the corresponding part in the main function. int isSpaceLeft (FOLDER);This function compares the free space of the disk with the size of folder given with the parameter list. The function shall return 1 if there is enough space to add the folder, otherwise 0 (just the result of the comparison). void SortByDate ();This function shall implement the InsertionSort using the component date as key. Use the provided algorithm/souce code of the exercise as template. If you need a comparison between dates, use the function isBefore you have written again. void addFolder (FOLDER);The function has to check if the disk has additional capacities to add the new folder (number of folders and space left). If at least one of these conditions is false print an error message and return -1. Else there has to be added an other test to avoid 2 folder elements with the same date (use the findByDate function here. If there is no folder with the new date simply attach the new folder at the end of the array and call the sorting algorithm afterwards to keep the order in the array. TEST: Now you can try to add a folder via the "a" in the menu. Activate the corresponding part in the main function. void delDir (int);This function removes one element of the disk array. The input parameter contains the index of the element to delete. Deletion can simply be done by moving all elements at the right one to the left (overwriting the element to delete. The function may get a -1. This has to be checked first (certainly there is nothing to delete then!) Don't forget to decrement the counter of elements at the end. TEST: Now you can try to remove a folder by date via the "r" in the menu. Activate the corresponding part in the main function. unsigned findAllOfLocation(char[], FOLDER[]);This is an optional additional task: The function shall find all elements with the given value for the component location (first input parameter). The array elements which are found have to be added to the FOLDER array (second input parameter). As this parameter is an array we can use the result later in the main function. There kernel of function implements a modified linear search on the disk array (it does not stop if one element is found bat continues search until the location of all elements is checked). The finally function shall return the number of elements found in the disk array. TEST: Now you can try to add a folder by date via the "l" in the menu. Activate the corresponding part in the main function.
What is d'n in c?
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