It is a compile time unary operator which can be used to compute the size of its operand. Usage sizeof operator is used in different way according to the operand type. When operand is a Data Type. When sizeof is used with the data types such as int, float, char… etc it simply returns the amount of memory is allocated to that data types. Note : sizeof may give different output according to machine, we have run our program on 32 bit gcc compiler.
When operand is an expression. When sizeof is used with the expression, it returns size of the expression. Let see example: C. As we know from first case size of int and diy light box display is 4 and 8 respectively, a is int variable while d is a double variable. The final result will be a double, Hence the output of our program is 8 bytes. Need of Sizeof 1. To find out number of elements in a array.
Sizeof can be used to calculate number of elements of the array automatically. Let see Example : C. To allocate a block of memory dynamically. We can allocate with the help of sizeof. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
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sizeof operator in C
It only takes a minute to sign up. I had to create a program that had a struct that held data inside of it. I had to read an input file and take the contents and read it into an array of structs. Then, I had to solve for some particular statistical data such as finding the lowest and highest scores from the data. I completed my source code and it runs and gives me the correct output, but I would like second opinions.
Please note that the comments are for my own personal benefit. Even though the source code easily allows readers to understand what is going on, I have included them to help myself stay organized.
Using functional decomposition, write a program to keep records and perform statistical analysis for a class of 9 students. There are 3 exams, each worth points, during the semester. Each student is identified by a 4-digit student ID with a first name and a last name and followed by three exam scores. You will read the input data from an input file scores. Each line of data for one student will be read from file and then assigned to a struct variable. Consequently, you will need an array of structs to store all the data read from the input file.
This will be a 1-dimensional array. Once you read data from the file to your array, you are required to calculate and display the following statistics for each exam. The statistics to be shown will be the:. It will be better to have an array for each statistic of size 3, that is an array for lowest values, and so on.
You may assume the scores from the file had been validated and they are all valid. The grade will be based on the total of all the 3 exams which will be out ofand grade will be as follows:. Putting using namespace std at the top of every program is a bad habit that you'd do well to avoid.
Know when to use it and when not to as when writing include headers. It's generally better to explicitly pass variables your function will need rather than using the vague implicit linkage of a global variable. For example, the calcLowest gets the StudentData array as a passed parameter -- the size of that array should also be passed.11 - Programming with C++ , Struct , Struct with functions,Struct with arrays برمجة
Size of what? What info? The first is that it is not portable to other operating systems which you may or may not care about now.
Do not use sizeof for array parameters
The second is that it's a security hole, which you absolutely must care about. Specifically, if some program is defined and named PAUSE or pauseyour program will execute that program instead of what you intend, and that other program could be anything. First, isolate these into a seperate functions pause and then modify your code to call those functions instead of system. For example:. This code could be made portable if, in addition to the changes in the previous point, you omit the Windows-only include files include "stdafx.
The code currently has a great number of variables that are serially numbered such as std1std2etc.Behold, here we have a simple array and we are printing all the elements in the array using a range-based for loop, and it actually works! Not surprising for many programmers but it's surprising for me. The advantage of using std::vector or std::array is that it's a class which holds the size of the internal array as a data member.
It's your responsibility as the programmer to carry around the size of the array with you whenever you want to loop through the array. I know that the name of the array is simply a pointer to the first element. Without having the size, once you start looping, you don't know when to stop because you don't necessarily know how far the array extends in memory.
And yet the range-based for loop works. How does it do that? If I have a number of threads that each do some calculations based on a joint read only array, will it be faster if I provide each array with a separate copy of that array. Of course I could just try it out, but I will first have to learn how to implement threads in the first place. I am kinda new to programming, so pardon me for any stupid questions :P, i noticed that when i write this.
The output is 0 afirstly why is the size 0? I might have overlooked something but i would be really appreciate if some could point out the cause.
Thank you. Is it guaranteed that thread two will see the value of non atomic x as If not, if I change the access to y to use load and store, will that make a difference? Is it guaranteed that thread two will see the result of all non atomic operations that come before thread one sets y to true? I have simple code: first thread pushes std::strings to the std::list, and second thread pops std::strings from this std::list.
This code permanently prints error to console: "Error: lst. Can someone please explain what are acquire and release semantics in memory accessing? My very first thought when hearing acquire and release was about something like mutex in application layer. Are those memory accessing model and mutex relevant things? And how are they related to load and store operations? In matlab, we can use a vector B to get the sublist of vector A by coding like A B. But in Eigen, I am wondering if there is anyway to do that?
I've searched the answer s to this question online but I have yet to find a satisfactory answer. I was wondering what are all the rules for initialization of objects of struct and class types, specifically when it comes to constructors vs braced initializer lists.
Are the rules different for structs vs classes too? I attempt to initialize Rectangle r the way you would usually do it in C, using a plain old braced initializer list. That is not very useful error message it seems at first glance. However I think that it has something to do with the constructor, because if I remove it, the code compiles and runs!
It would be a paradox I think, both the braced initializer list and the constructor are competing to initialize the data members it seems.The function fun receives an array parameter arr and tries to find out number of elements in arr using sizeof operator. In C, array parameters are treated as pointers See this for details. Therefore, sizeof should not be used to get number of elements in such cases.
A separate parameter for array size or length should be passed to fun. So the corrected program is:. Please write comments if you find anything incorrect in the above article or you want to share more information about the topic discussed above. Writing code in comment?
Please use ide. Implement Your Own sizeof How to count set bits in a floating point number in C? How to change the output of printf in main? What is the difference between single quoted and double quoted declaration of char array? How to dynamically allocate a 2D array in C? Must Do Coding Questions Company-wise. Consider the below program. Recommended Posts: Is sizeof for a struct equal to the sum of sizeof of each member? Why C treats array parameters as pointers?
Improved By : shohamziner. Load Comments.Forum: Beginning Java. Kd Martin. I have a few questions pertaining to this assignment I have.
Firstly, I'm having some trouble figuring out how to add a student to a course and keep an index of the courses the student is enrolled in. I also don't understand what exactly I am supposed to use the Student array for. The instructions said to add the setCapacity method but I don't know what that is supposed to be used for. A public method enrollStudent Student s to add s to this course and return true if the student was successfully added, or false if not A public method removeStudent Student s to remove s from the students array Part III: 20 pts Create a test class to check whether above classes work properly.
It should be able to create Course and Student objects, enroll student or drop student to these courses, printout current enrolled courses for a given student. Pranav Raulkar. I like Hi Kd Martin, In order to know which courses the student has enrolled to, you need to have something, ideally, an collection of Course objects in your student class.
Hope this helps. Campbell Ritchie. Why have you got a number field in the student class? You do not appear to use it for anything. Are you supposed to use that field to set the ID number? If you, you would not want to pass the ID to the constructor.
Have you got any way of getting courses from the student class? The question about which course a student enrols for sounds like something out of a database assignment, where you get a relation between student and course and you can query it both ways.
You can search through all the courses for a particular student, but that is hardly an elegant or efficient solution. You can try a bidirectional mapbut that is probably too complicated for your level of experience. You can add some way of recording courses inside the Student class, you can have students recorded in each course, and courses recorded in each student.The function fun receives an array parameter arr and tries to find out number of elements in arr using sizeof operator.
In C, array parameters are treated as pointers See this for details. Therefore, sizeof should not be used to get number of elements in such cases. A separate parameter for array size or length should be passed to fun. So the corrected program is:. Please write comments if you find anything incorrect in the above article or you want to share more information about the topic discussed above. Writing code in comment?
Please use ide. Implement Your Own sizeof How to count set bits in a floating point number in C? How to change the output of printf in main? What is the difference between single quoted and double quoted declaration of char array? How to dynamically allocate a 2D array in C? Deploy Python Flask App on Heroku. Consider the below program. Recommended Posts: Is sizeof for a struct equal to the sum of sizeof of each member?
Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Brevity isn't wise here, so I made some changes and laid everything out.
I'm still at my wits' end trying to figure this out and made some changes that was recommended. I'm trying to invoke the method in the driver program to add objects called students, defined in the Student-class, to be added to a roster found in the Course-class so the driver program can print out who is in the course. The Course-class has a method called addStudent which returns a boolean expression.
Depending if there is enough room to add the student, the student will be added. ArrayList-class is not allowed i. After all that, I get a hashcode, or a memory address, is printed. I would like this to be expandable so that when students becomes existent, then that too can easily be added to the course roster and so on.
You had it the other way round, your current code reads "if the capacity is more than or equal to 5 then add a new entry" when infact you want to say "if the capacity is NOT more than or equal to 5 add a new entry. Given the limited information I have from your question, I would assume that roster is a member of Course with the type Student which contains all students that are following the course.
I have no idea why you have another local two-dimensional array of String within addStudent method though. I would also suggest to return true for the method addStudent if the call is successful instead of the other way around. Learn more. How do I add students to a roster from different classes in Java?
Ask Question. Asked 4 years, 9 months ago. Active 4 years, 9 months ago. Viewed 2k times. S First post. Here's to not giving up. Francisco Francisco 21 5 5 bronze badges. First question: since the course roster is a list of students, why isn't it declared as a list or array of Student? I'm not sure why you're trying to make it a two-dimensional array of String.
That just complicates things. What is this code a part of? You should include at least outlines of your classes since the current version is difficult to follow.
Do not use sizeof for array parameters
Why is there a definition of addStudent in the middle of something that doesn't look like the Course class? String roster is local to the method and get garbage collected when you exit the function.
It should be outside this method. You will have to figure how to manipulate this array. Active Oldest Votes. You have a logic error in your code: if roster.
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