Programming Studio #12ECE 190Programming Studio #12• Topics this week:• Basic Data Structures• Enumerations• Dynamic Memory Allocation• In Studio Assignment– Complex Number AdderAnnouncements• MP 5– Challenging, so start early. – Checkpoint 1 Due date extended by 1 week• Exam 2– Regrade requests due today.• Final Exam– Monday May 10th– 1:30 – 4:30– Conflict Exam: Friday May 7th– 1:30 – 4:30 (see website to see if you are eligible for a conflict exam). Notify us by April 30thCheating• Reminder: We do not tolerate any form of cheating.– Sharing code is cheating– Sharing code and renaming variables is still cheating– Sharing code and adding/removing spaces/tabs is still cheating• We have identified multiple cheaters on MP3 and MP4…guilty parties will be notified soonData Structures• What are the basic data types in C?– Integer, float, double, character• What about data in the real world?– Also integer, float, double, characters– Data is often organized into groups• Vectors: direction, magnitude• Complex numbers: real part, complex part• Student record: last name, first name, UIN, GPA, standing…Structures• Grouping of primitive data types• Student Record ExampleFirst Name (char[])Last Name (char[])netID (char[])UIN (unsigned int)GPA (float)Student Record StructureJohnDoedoe11234567893.99Student 1SarahSmithSmith19876543214.00Student 2Structures• We must first define the customized data type (structure)• We can then create variables whose type is the structurestruct student_record {char first_name[12];char last_name[12];char netid[8];unsigned int uin;float gpa;};int main(){struct student_record student_1;student_1.first_name = ``John``;student_1.last_name = ‘’Doe’’;student_1.uin = 123456789;...}First Name (char[])Last Name (char[])netID (char[])UIN (unsigned int)GPA (float)Student Record StructureStructures• Memory is allocated the same way as for any variable– Locals are allocated on the run-time stack and globals are allocated on the global data section– Structures occupy contiguous regions of memory blocks. Each block takes as much memory as the sum of all of the member elements• How much space does each student entry take up?• Structure arrays can also be created:int main(){struct student_record students[100];student[0].first_name = ``John``;student[0].last_name = ‘’Doe’’;student[0].uin = 123456789;...}Structures and Pointers• Since structures are handled the same way as normal data types in C, pointers to structures can be created• The pointers can be dereferenced and accessed• Another way of accessing the values stored in pointers• The ‘->’ expression is like the dereference operator ‘*’ except it is used for dereferencing member elements of a structureint main(){struct student_recordstudents[100];struct student_record *st_ptr;st_ptr = &students[3];(*st_ptr).gpa = 3.25;st_ptr->gpa = 3.25;Enumerations• What if your data types should contain certain values?– Storing multiple choice answers (A,B,C,D)– Opcodes in an assembly language• You could just use an integer value to represent each of these things, but it is difficult to read for humans?– Which opcode is this? if(op == 2)• Solution: create a list where each number is assigned a human readable representation– This is much easier: if(op == LD)• Enumerated list: enum opcode {BR, ADD, LD};enum opcode op;op = 1;if(op == LD)Is this if statement true?Dynamic Memory Allocation• So far we know how to allocate memory using arrays– Limitation: we can only allocate a constant amount of elements– This amount must be known at compile time (specified in the source code)– Waste of memory, or danger of not allocating enough space to store all data• What if we want to allocate during run-time instead of compile time?Dynamic Memory Allocation• Use function “malloc(size)” to allocate memory at run time– Size is a parameter that tells malloc how many bytes to allocate– Memory is allocated in the heap• Dynamic memory must be freed manually using “free(<pointer>)”– <pointer> is a pointer to the memory block that needs to be freed– Without freeing no other programs/variables may use this memory block (we can run out of memory)int main(){struct student_record *students;int number;printf(``How many students?``);scanf(``%d``,&number);students = (student_record*) malloc(number * sizeof(student_record));/* students is now a pointer to the 0thelement of the ‘students’block */students[0].first_name = ``John``; /* behaves just like an array */students->last_name = ‘’Does’’;/* Code that initializes all student records */free(students);}Programming Studio Assignment• Complex number adder– Create a structure for a complex number (float real_part, float complex_part);– Ask the user how many complex numbers will be entered– Dynamically allocate enough space to hold all the complex numbers– Ask the user to enter each number (first ask for the real part, then ask for the complex part)– Add all the complex numbers together: • The real_part of the sum is just the sum of the real parts of all the numbers• The complex_part of the sum is just the sum of the complex parts of all the numbers– Print out the answer in the format: “Sum = <real_part> + j <complex_part>”– Remember to free the memory after you’re